1
|
Bertling K, Veidt M, Perchoux J, Rakić AD. Imaging elastic waves in solids: how to use laser feedback interferometry to visualize them. Opt Express 2023; 31:32761-32771. [PMID: 37859071 DOI: 10.1364/oe.497676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 09/07/2023] [Indexed: 10/21/2023]
Abstract
The use of ultrasonic elastic waves is a well established technique for non-destructive testing of materials and structures, in particular to exploit the interaction of waves with structural features to detect and characterize defects. Optical methods offer the advantage of visualising the distribution of elastic waves in a non-contact manner without disturbing the elastic wave. In this work we propose a laser feedback interferometry (LFI) based system as a cost effective, non-contact, alternative to a well established laser Doppler vibrometer technique. We demonstrate the visualization of the elastic waves, using an example of an elastic wave propagating through a prismatic acrylic rod. We show that the ultra-compact and simple implementation of LFI enables accurate visualization of the elastic waves in solids, and opens the pathway to a range of new opportunities in ultrasonic non-destructive testing and evaluation.
Collapse
|
2
|
Kashyap M, Torniainen J, Bertling K, Kundu U, Singh K, Donose BC, Gillespie T, Lim YL, Indjin D, Li L, Linfield EH, Davies AG, Dean P, Smith M, Chapman S, Bandyopadhyay A, Sengupta A, Rakić AD. Coherent terahertz laser feedback interferometry for hydration sensing in leaves. Opt Express 2023; 31:23877-23888. [PMID: 37475228 DOI: 10.1364/oe.490217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 06/08/2023] [Indexed: 07/22/2023]
Abstract
The response of terahertz to the presence of water content makes it an ideal analytical tool for hydration monitoring in agricultural applications. This study reports on the feasibility of terahertz sensing for monitoring the hydration level of freshly harvested leaves of Celtis sinensis by employing a imaging platform based on quantum cascade lasers and laser feedback interferometry. The imaging platform produces wide angle high resolution terahertz amplitude and phase images of the leaves at high frame rates allowing monitoring of dynamic water transport and other changes across the whole leaf. The complementary information in the resulting images was fed to a machine learning model aiming to predict relative water content from a single frame. The model was used to predict the change in hydration level over time. Results of the study suggest that the technique could have substantial potential in agricultural applications.
Collapse
|
3
|
Guo X, Degnan Z, Steele JA, Solano E, Donose BC, Bertling K, Fedorov A, Rakić AD, Jacobson P. Near-Field Localization of the Boson Peak on Tantalum Films for Superconducting Quantum Devices. J Phys Chem Lett 2023; 14:4892-4900. [PMID: 37199508 DOI: 10.1021/acs.jpclett.3c00850] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Superconducting circuits are among the most advanced quantum computing technologies; however, their performance is limited by losses found in surface oxides and disordered materials. In this work, we demonstrate the identification and spatial localization of a near-field signature of loss centers on tantalum films using terahertz scattering-type scanning near-field optical microscopy. By utilizing terahertz nanospectroscopy, we observe a localized excess vibrational mode around 0.5 THz and identify this resonance as the boson peak, a signature of amorphous materials. Grazing-incidence wide-angle X-ray scattering reveals that oxides on freshly solvent-cleaned samples are amorphous, whereas crystalline phases emerge after aging in air. Through nanoscale localization of defect centers, our findings provide valuable insights for the optimization of fabrication procedures for new low-loss superconducting circuits.
Collapse
Affiliation(s)
- Xiao Guo
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Zachary Degnan
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
- ARC Centre of Excellence for Engineered Quantum Systems, Brisbane, QLD 4072, Australia
| | - Julian A Steele
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
- cMACS, Department of Microbial and Molecular Systems, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Eduardo Solano
- NCD-SWEET Beamline, ALBA Synchrotron Light Source, Cerdanyola del Vallés, 08290 Barcelona, Spain
| | - Bogdan C Donose
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Arkady Fedorov
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
- ARC Centre of Excellence for Engineered Quantum Systems, Brisbane, QLD 4072, Australia
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Peter Jacobson
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
- ARC Centre of Excellence for Engineered Quantum Systems, Brisbane, QLD 4072, Australia
| |
Collapse
|
4
|
Qi X, Bertling K, Stark MS, Taimre T, Kao YC, Lim YL, Han S, O’Brien B, Collins A, Walsh M, Torniainen J, Gillespie T, Donose BC, Dean P, Li LH, Linfield EH, Davies AG, Indjin D, Soyer HP, Rakić AD. Terahertz imaging of human skin pathologies using laser feedback interferometry with quantum cascade lasers. Biomed Opt Express 2023; 14:1393-1410. [PMID: 37078035 PMCID: PMC10110320 DOI: 10.1364/boe.480615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 01/31/2023] [Accepted: 02/03/2023] [Indexed: 05/03/2023]
Abstract
Early detection of skin pathologies with current clinical diagnostic tools is challenging, particularly when there are no visible colour changes or morphological cues present on the skin. In this study, we present a terahertz (THz) imaging technology based on a narrow band quantum cascade laser (QCL) at 2.8 THz for human skin pathology detection with diffraction limited spatial resolution. THz imaging was conducted for three different groups of unstained human skin samples (benign naevus, dysplastic naevus, and melanoma) and compared to the corresponding traditional histopathologic stained images. The minimum thickness of dehydrated human skin that can provide THz contrast was determined to be 50 µm, which is approximately one half-wavelength of the THz wave used. The THz images from different types of 50 µm-thick skin samples were well correlated with the histological findings. The per-sample locations of pathology vs healthy skin can be separated from the density distribution of the corresponding pixels in the THz amplitude-phase map. The possible THz contrast mechanisms relating to the origin of image contrast in addition to water content were analyzed from these dehydrated samples. Our findings suggest that THz imaging could provide a feasible imaging modality for skin cancer detection that is beyond the visible.
Collapse
Affiliation(s)
- Xiaoqiong Qi
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Mitchell S. Stark
- The University of Queensland Diamantina Institute, The University of Queensland, Dermatology Research Centre, Brisbane, QLD 4102, Australia
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Yung-Ching Kao
- The University of Queensland Diamantina Institute, The University of Queensland, Dermatology Research Centre, Brisbane, QLD 4102, Australia
| | - Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - She Han
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Blake O’Brien
- Sullivan Nicolaides Pathology, Brisbane, QLD, Australia
| | - Angus Collins
- Sullivan Nicolaides Pathology, Brisbane, QLD, Australia
| | - Michael Walsh
- Sullivan Nicolaides Pathology, Brisbane, QLD, Australia
| | - Jari Torniainen
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Timothy Gillespie
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Bogdan C. Donose
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Lian He Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Edmund H. Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - A. Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - H. Peter Soyer
- The University of Queensland Diamantina Institute, The University of Queensland, Dermatology Research Centre, Brisbane, QLD 4102, Australia
- Department of Dermatology, Princess Alexandra Hospital, Brisbane, Queensland, Australia
| | - Aleksandar D. Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| |
Collapse
|
5
|
Singh K, Bandyopadhyay A, Bertling K, Lim YL, Gillespie T, Indjin D, Li L, Linfield EH, Davies AG, Dean P, Rakić AD, Sengupta A. Comparison of Physical and System Factors Impacting Hydration Sensing in Leaves Using Terahertz Time-Domain and Quantum Cascade Laser Feedback Interferometry Imaging. Sensors (Basel) 2023; 23:2721. [PMID: 36904925 PMCID: PMC10007308 DOI: 10.3390/s23052721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 02/24/2023] [Accepted: 02/28/2023] [Indexed: 06/18/2023]
Abstract
To reduce the water footprint in agriculture, the recent push toward precision irrigation management has initiated a sharp rise in photonics-based hydration sensing in plants in a non-contact, non-invasive manner. Here, this aspect of sensing was employed in the terahertz (THz) range for mapping liquid water in the plucked leaves of Bambusa vulgaris and Celtis sinensis. Two complementary techniques, broadband THz time-domain spectroscopic imaging and THz quantum cascade laser-based imaging, were utilized. The resulting hydration maps capture the spatial variations within the leaves as well as the hydration dynamics in various time scales. Although both techniques employed raster scanning to acquire the THz image, the results provide very distinct and different information. Terahertz time-domain spectroscopy provides rich spectral and phase information detailing the dehydration effects on the leaf structure, while THz quantum cascade laser-based laser feedback interferometry gives insight into the fast dynamic variation in dehydration patterns.
Collapse
Affiliation(s)
- Khushboo Singh
- Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Aparajita Bandyopadhyay
- DRDO-Industry-Academia Center of Excellence, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Karl Bertling
- School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Yah Leng Lim
- School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Tim Gillespie
- School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Lianhe Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Edmund H. Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - A. Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Aleksandar D. Rakić
- School of Information Technology & Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Amartya Sengupta
- Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| |
Collapse
|
6
|
Bertling K, Qi X, Taimre T, Lim YL, Rakić AD. Feedback Regimes of LFI Sensors: Experimental Investigations. Sensors (Basel) 2022; 22:9001. [PMID: 36433597 PMCID: PMC9696093 DOI: 10.3390/s22229001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/11/2022] [Accepted: 11/18/2022] [Indexed: 06/16/2023]
Abstract
In this article, we revisit the concept of optical feedback regimes in diode lasers and explore each regime experimentally from a somewhat unconventional point of view by relating the feedback regimes to the laser bias current and its optical feedback level. The results enable setting the operating conditions of the diode laser in different applications requiring operation in different feedback regimes. We experimentally explored and theoretically supported this relationship from the standard Lang and Kobayashi rate equation model for a laser diode under optical feedback. All five regimes were explored for two major types of laser diodes: inplane lasers and vertical-cavity surface emitting lasers. For both lasers, we mapped the self-mixing strength vs. drive current and feedback level, observed the differences in the shape of the self-mixing fringes between the two laser architectures and a general simulation, and monitored other parameters of the lasers with changing optical feedback.
Collapse
Affiliation(s)
- Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Xiaoqiong Qi
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Aleksandar D. Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| |
Collapse
|
7
|
Qi X, Loh HY, Taimre T, Bertling K, Indjin D, Rakić AD. Self-Pulsations in Terahertz Quantum Cascade Lasers under Strong Optical Feedback: The Effect of Multiple Reflections in the External Cavity. Sensors (Basel) 2022; 22:8501. [PMID: 36366193 PMCID: PMC9658095 DOI: 10.3390/s22218501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/29/2022] [Accepted: 11/03/2022] [Indexed: 06/16/2023]
Abstract
We have recently reported the self-pulsation phenomenon under strong optical feedback in terahertz (THz) quantum cascade lasers (QCLs). One important issue, however, we left open: the effect of multiple round trips in the external cavity on the laser response to feedback. Our current analysis also casts additional light on the phenomenon of self-pulsations. Using only one external cavity round trip (ECRT) in the model has been the common approach following the seminal paper by Lang-Kobayashi in 1980. However, the conditions under which the Lang-Kobayashi model, in its original single-ECRT formulation, is applicable has been rarely explored. In this work, we investigate the self-pulsation phenomenon under multiple ECRTs. We found that the self-pulsation waveform changes when considering more than one ECRT. This we attribute to the combined effect of the extended external cavity length and the frequency modulation of the pulsation frequency by the optical feedback. Our findings add to the understanding of the optical feedback dynamics under multiple ECRTs and provide a pathway for selecting the appropriate numerical model to study the optical feedback dynamics in THz QCLs and semiconductor lasers in general.
Collapse
Affiliation(s)
- Xiaoqiong Qi
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Hui Yi Loh
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Aleksandar D. Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| |
Collapse
|
8
|
Cometta S, Jones RT, Juárez-Saldivar A, Donose BC, Yasir M, Bock N, Dargaville TR, Bertling K, Brünig M, Rakić AD, Willcox M, Hutmacher DW. Melimine-Modified 3D-Printed Polycaprolactone Scaffolds for the Prevention of Biofilm-Related Biomaterial Infections. ACS Nano 2022; 16:16497-16512. [PMID: 36245096 PMCID: PMC9620410 DOI: 10.1021/acsnano.2c05812] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
Biomaterial-associated infections are one of the major causes of implant failure. These infections result from persistent bacteria that have adhered to the biomaterial surface before, during, or after surgery and have formed a biofilm on the implant's surface. It is estimated that 4 to 10% of implant surfaces are contaminated with bacteria; however, the infection rate can be as high as 30% in intensive care units in developed countries and as high as 45% in developing countries. To date, there is no clinical solution to prevent implant infection without relying on the use of high doses of antibiotics supplied systemically and/or removal of the infected device. In this study, melimine, a chimeric cationic peptide that has been tested in Phase I and II human clinical trials, was immobilized onto the surface of 3D-printed medical-grade polycaprolactone (mPCL) scaffolds via covalent binding and adsorption. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of melimine-treated surfaces confirmed immobilization of the peptide, as well as its homogeneous distribution throughout the scaffold surface. Amino acid analysis showed that melimine covalent and noncovalent immobilization resulted in a peptide density of ∼156 and ∼533 ng/cm2, respectively. Furthermore, we demonstrated that the immobilization of melimine on mPCL scaffolds by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride (EDC) coupling and noncovalent interactions resulted in a reduction of Staphylococcus aureus colonization by 78.7% and 76.0%, respectively, in comparison with the nonmodified control specimens. Particularly, the modified surfaces maintained their antibacterial properties for 3 days, which resulted in the inhibition of biofilm formation in vitro. This system offers a biomaterial strategy to effectively prevent biofilm-related infections on implant surfaces without relying on the use of prophylactic antibiotic treatment.
Collapse
Affiliation(s)
- Silvia Cometta
- Faculty
of Engineering, School of Mechanical, Medical and Process Engineering, Queensland University of Technology, Brisbane, QLD 4000, Australia
- Australian
Research Council Training Centre for Multiscale 3D Imaging, Modelling
and Manufacturing (M3D Innovation), Queensland
University of Technology, Kelvin
Grove, QLD 4059, Australia
- Max
Planck Queensland Centre, Queensland University
of Technology, Brisbane, QLD 4000, Australia
| | - Robert T. Jones
- Central
Analytical Research Facility (CARF), Queensland
University of Technology, Brisbane, QLD 4000, Australia
- Centre
for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4000, Australia
| | - Alfredo Juárez-Saldivar
- Unidad Académica
Multidisciplinaria Reynosa Aztlán, Universidad Autónoma de Tamaulipas, Reynosa 88740, Mexico
| | - Bogdan C. Donose
- School
of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Muhammad Yasir
- School
of Optometry and Vision Science, University
of New South Wales, Sydney, NSW 2033, Australia
| | - Nathalie Bock
- Australian
Research Council Training Centre for Multiscale 3D Imaging, Modelling
and Manufacturing (M3D Innovation), Queensland
University of Technology, Kelvin
Grove, QLD 4059, Australia
- Max
Planck Queensland Centre, Queensland University
of Technology, Brisbane, QLD 4000, Australia
- Faculty
of Health, School of Biomedical Sciences, Queensland University of Technology, Brisbane, QLD 4000, Australia
- Translational Research
Institute, Woolloongabba, QLD 4102, Australia
| | - Tim R. Dargaville
- Centre
for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4000, Australia
| | - Karl Bertling
- School
of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Michael Brünig
- School
of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Aleksandar D. Rakić
- School
of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Mark Willcox
- School
of Optometry and Vision Science, University
of New South Wales, Sydney, NSW 2033, Australia
| | - Dietmar W. Hutmacher
- Faculty
of Engineering, School of Mechanical, Medical and Process Engineering, Queensland University of Technology, Brisbane, QLD 4000, Australia
- Australian
Research Council Training Centre for Multiscale 3D Imaging, Modelling
and Manufacturing (M3D Innovation), Queensland
University of Technology, Kelvin
Grove, QLD 4059, Australia
- Max
Planck Queensland Centre, Queensland University
of Technology, Brisbane, QLD 4000, Australia
- Translational Research
Institute, Woolloongabba, QLD 4102, Australia
- Australian
Research Council Industrial Transformation Training Centre in Additive
Biomanufacturing, Queensland University
of Technology, Brisbane, QLD 4059, Australia
- Australian
Research Council Training Centre for Cell and Tissue Engineering Technologies, Queensland University of Technology, Brisbane, QLD 4059, Australia
| |
Collapse
|
9
|
Plöschner M, Morote MM, Dahl DS, Mounaix M, Light G, Rakić AD, Carpenter J. Spatial tomography of light resolved in time, spectrum, and polarisation. Nat Commun 2022; 13:4294. [PMID: 35879290 PMCID: PMC9314355 DOI: 10.1038/s41467-022-31814-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Accepted: 07/01/2022] [Indexed: 11/11/2022] Open
Abstract
Measuring polarisation, spectrum, temporal dynamics, and spatial complex amplitude of optical beams is essential to studying phenomena in laser dynamics, telecommunications and nonlinear optics. Current characterisation techniques apply in limited contexts. Non-interferometric methods struggle to distinguish spatial phase, while phase-sensitive approaches necessitate either an auxiliary reference source or a self-reference, neither of which is universally available. Deciphering complex wavefronts of multiple co-propagating incoherent fields remains particularly challenging. We harness principles of spatial state tomography to circumvent these limitations and measure a complete description of an unknown beam as a set of spectrally, temporally, and polarisation resolved spatial state density matrices. Each density matrix slice resolves the spatial complex amplitude of multiple mutually incoherent fields, which over several slices reveals the spectral or temporal evolution of these fields even when fields spectrally or temporally overlap. We demonstrate these features by characterising the spatiotemporal and spatiospectral output of a vertical-cavity surface-emitting laser. The work harnesses principles of spatial state tomography to fully characterise an optical beam in space, time, spectrum, and polarisation. Analysis of the output of a vertical-cavity surface-emitting laser illustrates the technique’s capabilities.
Collapse
Affiliation(s)
- Martin Plöschner
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia.
| | - Marcos Maestre Morote
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Daniel Stephen Dahl
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Mickael Mounaix
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Greta Light
- II-VI Incorporated, 48800 Milmont Dr., Fremont, CA, 94538, USA
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Joel Carpenter
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| |
Collapse
|
10
|
Qi X, Bertling K, Taimre T, Agnew G, Leng Lim Y, Gillespie T, Demić A, Dean P, He Li L, Linfield EH, Giles Davies A, Indjin D, Rakić AD. Terahertz quantum cascade laser under optical feedback: effects of laser self-pulsations on self-mixing signals. Opt Express 2021; 29:39885-39895. [PMID: 34809343 DOI: 10.1364/oe.437861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 09/27/2021] [Indexed: 06/13/2023]
Abstract
In this article, we explore the interplay between the self-pulsations (SPs) and self-mixing (SM) signals generated in terahertz (THz) quantum cascade lasers (QCLs) under optical feedback. We find that optical feedback dynamics in a THz QCL, namely, SPs, modulate the conventional SM interference fringes in a laser feedback interferometry system. The phenomenon of fringe loss in the SM signal - well known in interband diode lasers - was also observed along with pronounced SPs. With an increasing optical feedback strength, SM interference fringes transition from regular fringes at weak feedback (C ≤ 1) to fringes modulated by SPs under moderate feedback (1 < C ≤ 4.6), and then [under strong feedback (C > 4.6)] to a SM waveform with reduced number of fringes modulated by SP, until eventually (under even greater feedback) all the fringes are lost and only SPs are left visible. The transition route described above was identified in simulation when the SM fringes are created either by a moving target or a current modulation of the THz QCL. This SM signal transition route was successfully validated experimentally in a pulsed mode THz QCL with SM fringes created by current modulation during the pulse. The effects of SP dynamics in laser feedback interferometric system investigated in this work not only provides a further understanding of nonlinear dynamics in a THz QCL but also helps to understand the SM waveforms generated in a THz QCLs when they are used for various sensing and imaging applications.
Collapse
|
11
|
Solemanifar A, Guo X, Donose BC, Bertling K, Laycock B, Rakić AD. Probing peptide nanowire conductivity by THz nanoscopy. Nanotechnology 2021; 33:065503. [PMID: 34715680 DOI: 10.1088/1361-6528/ac34a6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/29/2021] [Indexed: 06/13/2023]
Abstract
Significant efforts have recently been invested in assessing the physical and chemical properties of microbial nanowires for their promising role in developing alternative renewable sources of electricity, bioelectronic materials and implantable sensors. One of their outstanding properties, the ever-desirable conductivity has been the focus of numerous studies. However, the lack of a straightforward and reliable method for measuring it seems to be responsible for the broad variability of the reported data. Routinely employed methods tend to underestimate or overestimate conductivity by several orders of magnitude. In this work, synthetic peptide nanowires conductivity is interrogated employing a non-destructive measurement technique developed on a terahertz scanning near-field microscope to test if peptide aromaticity leads to higher electrical conductivity. Our novel peptide conductivity measurement technique, based on triple standards calibration method, shows that in the case of two biopolymer mimicking peptides, the sample incorporating aromatic residues (W6) is about six times more conductive than the negative control (L6). To the best of our knowledge, this is the first report of a quantitative nano-scale terahertz s-SNOM investigation of peptides. These results prove the suitability of the terahertz radiation-based non-destructive approach in tandem with the designer peptides choice as model test subjects. This approach requires only simple sample preparation, avoids many of the pitfalls of typical contact-based conductivity measurement techniques and could help understanding fundamental aspects of nature's design of electron transfer in biopolymers.
Collapse
Affiliation(s)
- Armin Solemanifar
- School of Chemical Engineering, The University of Queensland, QLD 4072, Australia
| | - Xiao Guo
- School of Information Technology and Electrical Engineering, The University of Queensland, QLD 4072, Australia
| | - Bogdan C Donose
- School of Chemical Engineering, The University of Queensland, QLD 4072, Australia
- School of Information Technology and Electrical Engineering, The University of Queensland, QLD 4072, Australia
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, QLD 4072, Australia
| | - Bronwyn Laycock
- School of Chemical Engineering, The University of Queensland, QLD 4072, Australia
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, QLD 4072, Australia
| |
Collapse
|
12
|
Qi X, Agnew G, Taimre T, Han S, Lim YL, Bertling K, Demić A, Dean P, Indjin D, Rakić AD. Laser feedback interferometry in multi-mode terahertz quantum cascade lasers. Opt Express 2020; 28:14246-14262. [PMID: 32403467 DOI: 10.1364/oe.390433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 03/19/2020] [Indexed: 06/11/2023]
Abstract
The typical modal characteristics arising during laser feedback interferometry (LFI) in multi-mode terahertz (THz) quantum cascade lasers (QCLs) are investigated in this work. To this end, a set of multi-mode reduced rate equations with gain saturation for a general Fabry-Pérot multi-mode THz QCL under optical feedback is developed. Depending on gain bandwidth of the laser and optical feedback level, three different operating regimes are identified, namely a single-mode regime, a multi-mode regime, and a tuneable-mode regime. When the laser operates in the single-mode and multi-mode regimes, the self-mixing signal amplitude (peak to peak value of the self-mixing fringes) is proportional to the feedback coupling rate at each mode frequency. However, this rule no longer holds when the laser enters into the tuneable-mode regime, in which the feedback level becomes sufficiently strong (the boundary value of the feedback level depends on the gain bandwidth). The mapping of the identified feedback regimes of the multi-mode THz QCL in the space of the gain bandwidth and feedback level is investigated. In addition, the dependence of the aforementioned mapping of these three regimes on the linewidth enhancement factor of the laser is also explored, which provides a systematic picture of the potential of LFI in multi-mode THz QCLs for spectroscopic sensing applications.
Collapse
|
13
|
Keeley J, Bertling K, Rubino PL, Lim YL, Taimre T, Qi X, Kundu I, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG, Cunningham J, Dean P. Detection sensitivity of laser feedback interferometry using a terahertz quantum cascade laser. Opt Lett 2019; 44:3314-3317. [PMID: 31259948 DOI: 10.1364/ol.44.003314] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
We report on the high detection sensitivity of a laser feedback interferometry scheme based on a terahertz frequency quantum cascade laser (QCL). We show that variations on the laser voltage induced by optical feedback to the laser can be resolved with the reinjection of powers as low as ∼-125 dB of the emitted power. Our measurements demonstrate a noise equivalent power of ∼1.4 pW/√Hz, although, after accounting for the reinjection losses, we estimate that this corresponds to only ∼1 fW/√Hz being coupled to the QCL active region.
Collapse
|
14
|
Lim YL, Bertling K, Taimre T, Gillespie T, Glenn C, Robinson A, Indjin D, Han Y, Li L, Linfield EH, Davies AG, Dean P, Rakić AD. Coherent imaging using laser feedback interferometry with pulsed-mode terahertz quantum cascade lasers. Opt Express 2019; 27:10221-10233. [PMID: 31045166 DOI: 10.1364/oe.27.010221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/14/2019] [Indexed: 06/09/2023]
Abstract
We report a coherent terahertz (THz) imaging system that utilises a quantum cascade laser (QCL) operating in pulsed-mode as both the source and detector. The realisation of a short-pulsed THz QCL feedback interferometer permits both high peak powers and improved thermal efficiency, which enables the cryogen-free operation of the system. In this work, we demonstrated pulsed-mode swept-frequency laser feedback interferometry experimentally. Our interferometric detection scheme not only permits the simultaneous creation of both amplitude and phase images, but inherently suppresses unwanted background radiation. We demonstrate that the proposed system utilising microsecond pulses has the potential to achieve 0.25 mega-pixel per second acquisition rates, paving the pathway to video frame rate THz imaging.
Collapse
|
15
|
Keeley J, Freeman J, Bertling K, Lim YL, Mohandas RA, Taimre T, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG, Dean P. Publisher Correction: Measurement of the emission spectrum of a semiconductor laser using laser-feedback interferometry. Sci Rep 2018; 8:17648. [PMID: 30504784 PMCID: PMC6269521 DOI: 10.1038/s41598-018-36015-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|
16
|
Kundu I, Wang F, Qi X, Nong H, Dean P, Freeman JR, Valavanis A, Agnew G, Grier AT, Taimre T, Li L, Indjin D, Mangeney J, Tignon J, Dhillon SS, Rakić AD, Cunningham JE, Linfield EH, Davies AG. Author Correction: Ultrafast switch-on dynamics of frequency-tuneable semiconductor lasers. Nat Commun 2018; 9:5181. [PMID: 30504849 PMCID: PMC6269525 DOI: 10.1038/s41467-018-07629-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Affiliation(s)
- Iman Kundu
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| | - Feihu Wang
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Xiaoqiong Qi
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Hanond Nong
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Joshua R Freeman
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Alexander Valavanis
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Gary Agnew
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Andrew T Grier
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Lianhe Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Juliette Mangeney
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Jérôme Tignon
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Sukhdeep S Dhillon
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - John E Cunningham
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Edmund H Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - A Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| |
Collapse
|
17
|
Herbert J, Bertling K, Taimre T, Rakić AD, Wilson S. Microparticle discrimination using laser feedback interferometry. Opt Express 2018; 26:25778-25792. [PMID: 30469674 DOI: 10.1364/oe.26.025778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 08/30/2018] [Indexed: 06/09/2023]
Abstract
In this work, we present a method to discriminate between different microparticle sizes in mixed flowing media based on laser feedback interferometry, which could ultimately form the basis for a small, low-cost, real-time microembolus detector. We experimentally evaluated the performance of the system using microparticle phantoms, and the system achieved approximately 45% positive predictive value and better than 98% negative predictive value in the detection and classification of abnormally large particles.
Collapse
|
18
|
Kundu I, Wang F, Qi X, Nong H, Dean P, Freeman JR, Valavanis A, Agnew G, Grier AT, Taimre T, Li L, Indjin D, Mangeney J, Tignon J, Dhillon SS, Rakić AD, Cunningham JE, Linfield EH, Davies AG. Ultrafast switch-on dynamics of frequency-tuneable semiconductor lasers. Nat Commun 2018; 9:3076. [PMID: 30082762 PMCID: PMC6078980 DOI: 10.1038/s41467-018-05601-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 07/13/2018] [Indexed: 12/02/2022] Open
Abstract
Single-mode frequency-tuneable semiconductor lasers based on monolithic integration of multiple cavity sections are important components, widely used in optical communications, photonic integrated circuits and other optical technologies. To date, investigations of the ultrafast switching processes in such lasers, essential to reduce frequency cross-talk, have been restricted to the observation of intensity switching over nanosecond-timescales. Here, we report coherent measurements of the ultrafast switch-on dynamics, mode competition and frequency selection in a monolithic frequency-tuneable laser using coherent time-domain sampling of the laser emission. This approach allows us to observe hopping between lasing modes on picosecond-timescales and the temporal evolution of transient multi-mode emission into steady-state single mode emission. The underlying physics is explained through a full multi-mode, temperature-dependent carrier and photon transport model. Our results show that the fundamental limit on the timescales of frequency-switching between competing modes varies with the underlying Vernier alignment of the laser cavity. Single-mode, tuneable monolithic semiconductor lasers are important light sources for integrated photonics. Here, Kundu et al. observe the switch-on dynamics and mode competition of a terahertz quantum cascade laser and explain the behaviour with a carrier and photon transport model.
Collapse
Affiliation(s)
- Iman Kundu
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| | - Feihu Wang
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Xiaoqiong Qi
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Hanond Nong
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Joshua R Freeman
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Alexander Valavanis
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Gary Agnew
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Andrew T Grier
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Lianhe Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Juliette Mangeney
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Jérôme Tignon
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Sukhdeep S Dhillon
- Laboratoire Pierre Aigrain, Département de physique de l'ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, 75005, Paris, France
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - John E Cunningham
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Edmund H Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - A Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| |
Collapse
|
19
|
Mowla A, Du BW, Taimre T, Bertling K, Wilson S, Rakić AD. Polarization-sensitive laser feedback interferometry for specular reflection removal. Appl Opt 2018; 57:4067-4074. [PMID: 29791380 DOI: 10.1364/ao.57.004067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 04/21/2018] [Indexed: 06/08/2023]
Abstract
Specular reflection from the surface of targets or prepared specimens represents a significant problem in optical microscopy and related optical imaging techniques as usually the surface reflection does not contribute to the desired signal. Solutions exist for many of these imaging techniques; however, remedial techniques for imaging based on laser feedback interferometry (LFI) are absent. We propose a reflection cancellation technique based on crossed-polarization filtering that is tailored for a typical LFI configuration. The technique is validated with three experimental designs, and a significant improvement of about 40 dB in the ratio of the diffuse and specular LFI signal is observed. Applications of this principle extend from specular reflection removal to characterization of target materials in industrial to biomedical domains.
Collapse
|
20
|
Mowla A, Du BW, Taimre T, Bertling K, Wilson S, Soyer HP, Rakić AD. Confocal laser feedback tomography for skin cancer detection. Biomed Opt Express 2017; 8:4037-4048. [PMID: 28966845 PMCID: PMC5611921 DOI: 10.1364/boe.8.004037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/21/2017] [Accepted: 07/27/2017] [Indexed: 06/07/2023]
Abstract
Tomographic imaging of soft tissue such as skin has a potential role in cancer detection. The penetration of infrared wavelengths makes a confocal approach based on laser feedback interferometry feasible. We present a compact system using a semiconductor laser as both transmitter and receiver. Numerical and physical models based on the known optical properties of keratinocyte cancers were developed. We validated the technique on three phantoms containing macro-structural changes in optical properties. Experimental results were in agreement with numerical simulations and structural changes were evident which would permit discrimination of healthy tissue and tumour. Furthermore, cancer type discrimination was also able to be visualized using this imaging technique.
Collapse
Affiliation(s)
- Alireza Mowla
- The University of Queensland, School of Information Technology and Electrical Engineering, St. Lucia, Brisbane, 4072,
Australia
| | - Benjamin Wensheng Du
- The University of Queensland, School of Information Technology and Electrical Engineering, St. Lucia, Brisbane, 4072,
Australia
| | - Thomas Taimre
- The University of Queensland, School of Mathematics and Physics, St. Lucia, Brisbane, 4072,
Australia
| | - Karl Bertling
- The University of Queensland, School of Information Technology and Electrical Engineering, St. Lucia, Brisbane, 4072,
Australia
| | - Stephen Wilson
- The University of Queensland, School of Information Technology and Electrical Engineering, St. Lucia, Brisbane, 4072,
Australia
| | - H. Peter Soyer
- Dermatology Research Centre, The University of Queensland, The University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, 4102,
Australia
| | - Aleksandar D. Rakić
- The University of Queensland, School of Information Technology and Electrical Engineering, St. Lucia, Brisbane, 4072,
Australia
| |
Collapse
|
21
|
Keeley J, Freeman J, Bertling K, Lim YL, Mohandas RA, Taimre T, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG, Dean P. Measurement of the emission spectrum of a semiconductor laser using laser-feedback interferometry. Sci Rep 2017; 7:7236. [PMID: 28775327 PMCID: PMC5543105 DOI: 10.1038/s41598-017-07432-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 06/28/2017] [Indexed: 11/09/2022] Open
Abstract
The effects of optical feedback (OF) in lasers have been observed since the early days of laser development. While OF can result in undesirable and unpredictable operation in laser systems, it can also cause measurable perturbations to the operating parameters, which can be harnessed for metrological purposes. In this work we exploit this 'self-mixing' effect to infer the emission spectrum of a semiconductor laser using a laser-feedback interferometer, in which the terminal voltage of the laser is used to coherently sample the reinjected field. We demonstrate this approach using a terahertz frequency quantum cascade laser operating in both single- and multiple-longitudinal mode regimes, and are able to resolve spectral features not reliably resolved using traditional Fourier transform spectroscopy. We also investigate quantitatively the frequency perturbation of individual laser modes under OF, and find excellent agreement with predictions of the excess phase equation central to the theory of lasers under OF.
Collapse
Affiliation(s)
- James Keeley
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Joshua Freeman
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Reshma A Mohandas
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Lianhe H Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Edmund H Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - A Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| |
Collapse
|
22
|
Qi X, Agnew G, Kundu I, Taimre T, Lim YL, Bertling K, Dean P, Grier A, Valavanis A, Linfield EH, Giles Davies A, Indjin D, Rakić AD. Multi-spectral terahertz sensing: proposal for a coupled-cavity quantum cascade laser based optical feedback interferometer. Opt Express 2017; 25:10153-10165. [PMID: 28468390 DOI: 10.1364/oe.25.010153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 03/20/2017] [Indexed: 06/07/2023]
Abstract
We propose a laser feedback interferometer operating at multiple terahertz (THz) frequency bands by using a pulsed coupled-cavity THz quantum cascade laser (QCL) under optical feedback. A theoretical model that contains multi-mode reduced rate equations and thermal equations is presented, which captures the interplay between electro-optical, thermal, and feedback effects. By using the self-heating effect in both active and passive cavities, self-mixing signal responses at three different THz frequency bands are predicted. A multi-spectral laser feedback interferometry system based on such a coupled-cavity THz QCL will permit ultra-high-speed sensing and spectroscopic applications including material identification.
Collapse
|
23
|
Grier A, Dean P, Valavanis A, Keeley J, Kundu I, Cooper JD, Agnew G, Taimre T, Lim YL, Bertling K, Rakić AD, Li LH, Harrison P, Linfield EH, Ikonić Z, Davies AG, Indjin D. Origin of terminal voltage variations due to self-mixing in terahertz frequency quantum cascade lasers. Opt Express 2016; 24:21948-21956. [PMID: 27661929 DOI: 10.1364/oe.24.021948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 08/13/2016] [Indexed: 06/06/2023]
Abstract
We explain the origin of voltage variations due to self-mixing in a terahertz (THz) frequency quantum cascade laser (QCL) using an extended density matrix (DM) approach. Our DM model allows calculation of both the current-voltage (I-V) and optical power characteristics of the QCL under optical feedback by changing the cavity loss, to which the gain of the active region is clamped. The variation of intra-cavity field strength necessary to achieve gain clamping, and the corresponding change in bias required to maintain a constant current density through the heterostructure is then calculated. Strong enhancement of the self-mixing voltage signal due to non-linearity of the (I-V) characteristics is predicted and confirmed experimentally in an exemplar 2.6 THz bound-to-continuum QCL.
Collapse
|
24
|
Agnew G, Grier A, Taimre T, Lim YL, Bertling K, Ikonić Z, Valavanis A, Dean P, Cooper J, Khanna SP, Lachab M, Linfield EH, Davies AG, Harrison P, Indjin D, Rakić AD. Model for a pulsed terahertz quantum cascade laser under optical feedback. Opt Express 2016; 24:20554-20570. [PMID: 27607659 DOI: 10.1364/oe.24.020554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor lasers are operated using pulsed-mode excitation, their behavior under optical feedback depends on the electronic and thermal characteristics of the laser, as well as the nature of the external cavity. Predicting the behavior of a laser under both optical feedback and pulsed operation therefore requires a detailed model that includes laser-specific thermal and electronic characteristics. In this paper we introduce such a model for an exemplar bound-to-continuum terahertz frequency quantum cascade laser (QCL), illustrating its use in a selection of pulsed operation scenarios. Our results demonstrate significant interplay between electro-optical, thermal, and feedback phenomena, and that this interplay is key to understanding QCL behavior in pulsed applications. Further, our results suggest that for many types of QCL in interferometric applications, thermal modulation via low duty cycle pulsed operation would be an alternative to commonly used adiabatic modulation.
Collapse
|
25
|
Mowla A, Taimre T, Lim YL, Bertling K, Wilson SJ, Prow TW, Soyer HP, Rakić AD. Concurrent Reflectance Confocal Microscopy and Laser Doppler Flowmetry to Improve Skin Cancer Imaging: A Monte Carlo Model and Experimental Validation. Sensors (Basel) 2016; 16:E1411. [PMID: 27598157 PMCID: PMC5038689 DOI: 10.3390/s16091411] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 08/25/2016] [Accepted: 08/26/2016] [Indexed: 11/16/2022]
Abstract
Optical interrogation of suspicious skin lesions is standard care in the management of skin cancer worldwide. Morphological and functional markers of malignancy are often combined to improve expert human diagnostic power. We propose the evaluation of the combination of two independent optical biomarkers of skin tumours concurrently. The morphological modality of reflectance confocal microscopy (RCM) is combined with the functional modality of laser Doppler flowmetry, which is capable of quantifying tissue perfusion. To realize the idea, we propose laser feedback interferometry as an implementation of RCM, which is able to detect the Doppler signal in addition to the confocal reflectance signal. Based on the proposed technique, we study numerical models of skin tissue incorporating two optical biomarkers of malignancy: (i) abnormal red blood cell velocities and concentrations and (ii) anomalous optical properties manifested through tissue confocal reflectance, using Monte Carlo simulation. We also conduct a laboratory experiment on a microfluidic channel containing a dynamic turbid medium, to validate the efficacy of the technique. We quantify the performance of the technique by examining a signal to background ratio (SBR) in both the numerical and experimental models, and it is shown that both simulated and experimental SBRs improve consistently using this technique. This work indicates the feasibility of an optical instrument, which may have a role in enhanced imaging of skin malignancies.
Collapse
Affiliation(s)
- Alireza Mowla
- School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Brisbane 4072, Australia.
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, St. Lucia, Brisbane 4072, Australia.
| | - Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Brisbane 4072, Australia.
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Brisbane 4072, Australia.
| | - Stephen J Wilson
- School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Brisbane 4072, Australia.
| | - Tarl W Prow
- Dermatology Research Centre, The University of Queensland, School of Medicine, Translational Research Institute, Brisbane 4102, Australia.
| | - H Peter Soyer
- Dermatology Research Centre, The University of Queensland, School of Medicine, Translational Research Institute, Brisbane 4102, Australia.
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, St. Lucia, Brisbane 4072, Australia.
| |
Collapse
|
26
|
Han S, Bertling K, Dean P, Keeley J, Burnett AD, Lim YL, Khanna SP, Valavanis A, Linfield EH, Davies AG, Indjin D, Taimre T, Rakić AD. Laser Feedback Interferometry as a Tool for Analysis of Granular Materials at Terahertz Frequencies: Towards Imaging and Identification of Plastic Explosives. Sensors (Basel) 2016; 16:E352. [PMID: 27005629 PMCID: PMC4813927 DOI: 10.3390/s16030352] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 02/22/2016] [Accepted: 03/04/2016] [Indexed: 11/16/2022]
Abstract
We propose a self-consistent method for the analysis of granular materials at terahertz (THz) frequencies using a quantum cascade laser. The method is designed for signals acquired from a laser feedback interferometer, and applied to non-contact reflection-mode sensing. Our technique is demonstrated using three plastic explosives, achieving good agreement with reference measurements obtained by THz time-domain spectroscopy in transmission geometry. The technique described in this study is readily scalable: replacing a single laser with a small laser array, with individual lasers operating at different frequencies will enable unambiguous identification of select materials. This paves the way towards non-contact, reflection-mode analysis and identification of granular materials at THz frequencies using quantum cascade lasers.
Collapse
Affiliation(s)
- She Han
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia.
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia.
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - James Keeley
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - Andrew D Burnett
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
- School of Chemistry, University of Leeds, Leeds LS2 9JT, UK.
| | - Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia.
| | - Suraj P Khanna
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - Alexander Valavanis
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - Edmund H Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - A Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK.
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane QLD 4072, Australia.
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia.
| |
Collapse
|
27
|
Nikolić M, Lim YL, Bertling K, Taimre T, Rakić AD. Multiple signal classification for self-mixing flowmetry. Appl Opt 2015; 54:2193-2198. [PMID: 25968500 DOI: 10.1364/ao.54.002193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 02/04/2015] [Indexed: 06/04/2023]
Abstract
For the first time to our knowledge, we apply the multiple signal classification (MUSIC) algorithm to signals obtained from a self-mixing flow sensor. We find that MUSIC accurately extracts the fluid velocity and exhibits a markedly better signal-to-noise ratio (SNR) than the commonly used fast Fourier transform (FFT) method. We compare the performance of the MUSIC and FFT methods for three decades of scatterer concentration and fluid velocities from 0.5 to 50 mm/s. MUSIC provided better linearity than the FFT and was able to accurately function over a wider range of algorithm parameters. MUSIC exhibited excellent linearity and SNR even at low scatterer concentration, at which the FFT's SNR decreased to impractical levels. This makes MUSIC a particularly attractive method for flow measurement systems with a low density of scatterers such as microfluidic and nanofluidic systems and blood flow in capillaries.
Collapse
|
28
|
Keeley J, Dean P, Valavanis A, Bertling K, Lim YL, Alhathlool R, Taimre T, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG. Three-dimensional terahertz imaging using swept-frequency feedback interferometry with a quantum cascade laser. Opt Lett 2015; 40:994-997. [PMID: 25768165 DOI: 10.1364/ol.40.000994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate coherent three-dimensional terahertz imaging by frequency modulation of a quantum cascade laser in a compact and experimentally simple self-mixing scheme. Through this approach, we can realize significantly faster acquisition rates compared to previous schemes employing longitudinal mechanical scanning of a sample. We achieve a depth resolution of better than 0.1 μm with a power noise spectral density below -50 dB/Hz, for a sampling time of 10 ms/pixel.
Collapse
|
29
|
Dean P, Keeley J, Valavanis A, Bertling K, Lim YL, Taimre T, Alhathlool R, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG. Active phase-nulling of the self-mixing phase in a terahertz frequency quantum cascade laser. Opt Lett 2015; 40:950-953. [PMID: 25768154 DOI: 10.1364/ol.40.000950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate an active phase-nulling scheme for terahertz (THz) frequency quantum cascade lasers (QCLs) under optical feedback, by active electronic feedback control of the emission frequency. Using this scheme, the frequency tuning rate of a THz QCL is characterized, with significantly reduced experimental complexity compared to alternative approaches. Furthermore, we demonstrate real-time displacement sensing of targets, overcoming the resolution limits imposed by quantization in previously implemented fringe-counting methods. Our approach is readily applicable to high-frequency vibrometry and surface profiling of targets, as well as frequency-stabilization schemes for THz QCLs.
Collapse
|
30
|
Al Roumy J, Perchoux J, Lim YL, Taimre T, Rakić AD, Bosch T. Effect of injection current and temperature on signal strength in a laser diode optical feedback interferometer. Appl Opt 2015; 54:312-318. [PMID: 25967631 DOI: 10.1364/ao.54.000312] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/28/2014] [Indexed: 06/04/2023]
Abstract
We present a simple analytical model that describes the injection current and temperature dependence of optical feedback interferometry signal strength for a single-mode laser diode. The model is derived from the Lang and Kobayashi rate equations, and is developed both for signals acquired from the monitoring photodiode (proportional to the variations in optical power) and for those obtained by amplification of the corresponding variations in laser voltage. The model shows that both the photodiode and the voltage signal strengths are dependent on the laser slope efficiency, which itself is a function of the injection current and the temperature. Moreover, the model predicts that the photodiode and voltage signal strengths depend differently on injection current and temperature. This important model prediction was proven experimentally for a near-infrared distributed feedback laser by measuring both types of signals over a wide range of injection currents and temperatures. Therefore, this simple model provides important insight into the radically different biasing strategies required to achieve optimal sensor sensitivity for both interferometric signal acquisition schemes.
Collapse
|
31
|
Mowla A, Nikolić M, Taimre T, Tucker JR, Lim YL, Bertling K, Rakić AD. Effect of the optical system on the Doppler spectrum in laser-feedback interferometry. Appl Opt 2015; 54:18-26. [PMID: 25967002 DOI: 10.1364/ao.54.000018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 11/15/2014] [Indexed: 06/04/2023]
Abstract
We present a comprehensive analysis of factors influencing the morphology of the Doppler spectrum obtained from a laser-feedback interferometer. We explore the effect of optical system parameters on three spectral characteristics: central Doppler frequency, broadening, and signal-to-noise ratio. We perform four sets of experiments and replicate the results using a Monte Carlo simulation calibrated to the backscattering profile of the target. We classify the optical system parameters as having a strong or weak influence on the Doppler spectrum. The calibrated Monte Carlo approach accurately reproduces experimental results, and allows one to investigate the detailed contribution of system parameters to the Doppler spectrum, which are difficult to isolate in experiment.
Collapse
|
32
|
Bertling K, Perchoux J, Taimre T, Malkin R, Robert D, Rakić AD, Bosch T. Imaging of acoustic fields using optical feedback interferometry. Opt Express 2014; 22:30346-30356. [PMID: 25606963 DOI: 10.1364/oe.22.030346] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This study introduces optical feedback interferometry as a simple and effective technique for the two-dimensional visualisation of acoustic fields. We present imaging results for several pressure distributions including those for progressive waves, standing waves, as well as the diffraction and interference patterns of the acoustic waves. The proposed solution has the distinct advantage of extreme optical simplicity and robustness thus opening the way to a low cost acoustic field imaging system based on mass produced laser diodes.
Collapse
|
33
|
Lim YL, Taimre T, Bertling K, Dean P, Indjin D, Valavanis A, Khanna SP, Lachab M, Schaider H, Prow TW, Peter Soyer H, Wilson SJ, Linfield EH, Giles Davies A, Rakić AD. High-contrast coherent terahertz imaging of porcine tissue via swept-frequency feedback interferometry. Biomed Opt Express 2014; 5:3981-9. [PMID: 25426324 PMCID: PMC4242032 DOI: 10.1364/boe.5.003981] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 09/10/2014] [Accepted: 10/12/2014] [Indexed: 05/19/2023]
Abstract
There is considerable interest in the interrogation of biological tissue at terahertz (THz) frequencies, largely due to the contrast in the optical properties of different biological tissues which occur in this electro-magnetic radiation band. Of particular interest are THz biomedical images, which have the potential to highlight different information than those acquired in other frequency bands, thereby providing an augmented picture of biological structures. In this work, we demonstrate the feasibility of an interferometric biological imaging technique using a THz quantum cascade laser (QCL) operating at 2.59 THz to perform coherent imaging of porcine tissue samples. We show the potential of this new THz biomedical imaging technique for in vivo studies, by virtue of its reflection geometry and useful tissue penetration depth enabled by the large THz powers emitted by the quantum cascade laser used in this work. The observed clustering of interferometric tissue signatures opens a pathway towards automatic techniques for the discrimination of healthy tissue types for the study of normal physiology and possible therapeutic approaches.
Collapse
Affiliation(s)
- Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072,
Australia
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072,
Australia
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072,
Australia
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - Alexander Valavanis
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - Suraj P. Khanna
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - Mohammad Lachab
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - Helmut Schaider
- Dermatology Research Centre, The University of Queensland, School of Medicine, Translational Research Institute, Brisbane, QLD 4102,
Australia
| | - Tarl W. Prow
- Dermatology Research Centre, The University of Queensland, School of Medicine, Translational Research Institute, Brisbane, QLD 4102,
Australia
| | - H. Peter Soyer
- Dermatology Research Centre, The University of Queensland, School of Medicine, Translational Research Institute, Brisbane, QLD 4102,
Australia
| | - Stephen J. Wilson
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072,
Australia
| | - Edmund H. Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - A. Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT,
UK
| | - Aleksandar D. Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072,
Australia
| |
Collapse
|
34
|
Rakić AD, Taimre T, Bertling K, Lim YL, Wilson SJ, Nikolić M, Valavanis A, Indjin D, Linfield EH, Davies AG, Ferguson B, Walker G, Schaider H, Soyer HP. THz QCL self-mixing interferometry for biomedical applications. ACTA ACUST UNITED AC 2014. [DOI: 10.1117/12.2061433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
|
35
|
Taimre T, Bertling K, Lim YL, Dean P, Indjin D, Rakić AD. Methodology for materials analysis using swept-frequency feedback interferometry with terahertz frequency quantum cascade lasers. Opt Express 2014; 22:18633-18647. [PMID: 25089482 DOI: 10.1364/oe.22.018633] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Recently, we demonstrated an interferometric materials analysis scheme at terahertz frequencies based on the self-mixing effect in terahertz quantum cascade lasers. Here, we examine the impact of variations in laser operating parameters, target characteristics, laser-target system properties, and the quality calibration standards on our scheme. We show that our coherent scheme is intrinsically most sensitive to fluctuations in interferometric phase, arising primarily from variations in external cavity length. Moreover we demonstrate that the smallest experimental uncertainties in the determination of extinction coefficients are expected for lossy materials.
Collapse
|
36
|
Kliese R, Taimre T, Bakar AAA, Lim YL, Bertling K, Nikolić M, Perchoux J, Bosch T, Rakić AD. Solving self-mixing equations for arbitrary feedback levels: a concise algorithm. Appl Opt 2014; 53:3723-3736. [PMID: 24921138 DOI: 10.1364/ao.53.003723] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 04/28/2014] [Indexed: 06/03/2023]
Abstract
Self-mixing laser sensors show promise for a wide range of sensing applications, including displacement, velocimetry, and fluid flow measurements. Several techniques have been developed to simulate self-mixing signals; however, a complete and succinct process for synthesizing self-mixing signals has so far been absent in the open literature. This article provides a systematic numerical approach for the analysis of self-mixing sensors using the steady-state solution to the Lang and Kobayashi model. Examples are given to show how this method can be used to synthesize self-mixing signals for arbitrary feedback levels and for displacement, distance, and velocity measurement. We examine these applications with a deterministic stimulus and discuss the velocity measurement of a rough surface, which necessitates the inclusion of a random stimulus.
Collapse
|
37
|
Lui HS, Taimre T, Bertling K, Lim YL, Dean P, Khanna SP, Lachab M, Valavanis A, Indjin D, Linfield EH, Davies AG, Rakić AD. Terahertz inverse synthetic aperture radar imaging using self-mixing interferometry with a quantum cascade laser. Opt Lett 2014; 39:2629-2632. [PMID: 24784063 DOI: 10.1364/ol.39.002629] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We propose a terahertz (THz)-frequency synthetic aperture radar imaging technique based on self-mixing (SM) interferometry, using a quantum cascade laser. A signal processing method is employed which extracts and exploits the radar-related information contained in the SM signals, enabling the creation of THz images with improved spatial resolution. We demonstrate this by imaging a standard resolution test target, achieving resolution beyond the diffraction limit.
Collapse
|
38
|
Taimre T, Rakić AD. On the nature of Acket's characteristic parameter C in semiconductor lasers. Appl Opt 2014; 53:1001-1006. [PMID: 24663282 DOI: 10.1364/ao.53.001001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 01/03/2014] [Indexed: 06/03/2023]
Abstract
Quasi-static interferometric signals in lasers under feedback arise from slowly varying perturbations of the intracavity electric field resulting from the reinjection of a portion of the emitted field into the cavity. Such interferometric signals are well described by the steady-state solution to the Lang-Kobayashi rate equation model. We give an exact series expansion for this steady-state solution that shows precisely how Acket's characteristic parameter C and Henry's linewidth enhancement factor α influence such signals. We show how the series coefficients can be extracted easily and explain how to determine C and α directly from them. Moreover, we draw a precise analogy between self-mixing and FM signals, showing that C plays exactly the same role in self-mixing as the modulation index does in FM.
Collapse
|
39
|
Tucker JR, Mowla A, Herbert J, Fuentes MA, Freakley CS, Bertling K, Lim YL, Matharu RS, Perchoux J, Taimre T, Wilson SJ, Rakić AD. Self-mixing sensing system based on uncooled vertical-cavity surface-emitting laser array: linking multichannel operation and enhanced performance. Opt Lett 2014; 39:394-397. [PMID: 24562155 DOI: 10.1364/ol.39.000394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We compare the performance of a self-mixing (SM) sensing system based on an uncooled monolithic array of 24×1 vertical-cavity surface-emitting lasers (VCSELs) in two modes of operation: single active channel and the concurrent multichannel operation. We find that the signal-to-noise ratio of individual SM sensors in a VCSEL array is markedly improved by multichannel operation, as a consequence of the increased operational temperature of the sensors. The performance improvement can be further increased by manufacturing VCSEL arrays with smaller pitch. This has the potential to produce an imaging system with high spatial and temporal resolutions that can be operated without temperature stabilization.
Collapse
|
40
|
Nikolić M, Hicks E, Lim YL, Bertling K, Rakić AD. Self-mixing laser Doppler flow sensor: an optofluidic implementation. Appl Opt 2013; 52:8128-8133. [PMID: 24513768 DOI: 10.1364/ao.52.008128] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 10/18/2013] [Indexed: 06/03/2023]
Abstract
We present the miniaturization of self-mixing interferometry (SMI) into a microfluidic circuit using an optical fiber, forming an optofluidic device that can be used as a component in lab on a chip systems. We characterize the performance of the device as a fluid velocity (and hence flow) sensor, showing it to produce good accuracy and correlation with theory over a range of velocities from 0.5 to 60 mm/s and almost four decades of scatterer concentration. SMI in an optofluidic system has the advantage that only a single path to the optical inspection point is needed, as the laser source is also the receiver of light. In addition, the same system that is used for measuring fluid velocity can be used to measure other quantities such as particle size. The configuration presented is inherently easy to optically align due to the self-aligned property of SMI and divergent nature of light exiting the embedded optical fiber, providing for low-cost manufacturing.
Collapse
|
41
|
Rakić AD, Taimre T, Bertling K, Lim YL, Dean P, Indjin D, Ikonić Z, Harrison P, Valavanis A, Khanna SP, Lachab M, Wilson SJ, Linfield EH, Davies AG. Swept-frequency feedback interferometry using terahertz frequency QCLs: a method for imaging and materials analysis. Opt Express 2013; 21:22194-22205. [PMID: 24104111 DOI: 10.1364/oe.21.022194] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of high-power radiation with a narrow intrinsic linewidth. As such, THz QCLs are extremely promising sources for applications including high-resolution spectroscopy, heterodyne detection, and coherent imaging. We exploit the remarkable phase-stability of THz QCLs to create a coherent swept-frequency delayed self-homodyning method for both imaging and materials analysis, using laser feedback interferometry. Using our scheme we obtain amplitude-like and phase-like images with minimal signal processing. We determine the physical relationship between the operating parameters of the laser under feedback and the complex refractive index of the target and demonstrate that this coherent detection method enables extraction of complex refractive indices with high accuracy. This establishes an ultimately compact and easy-to-implement THz imaging and materials analysis system, in which the local oscillator, mixer, and detector are all combined into a single laser.
Collapse
|
42
|
Nikolić M, Jovanović DP, Lim YL, Bertling K, Taimre T, Rakić AD. Approach to frequency estimation in self-mixing interferometry: multiple signal classification. Appl Opt 2013; 52:3345-3350. [PMID: 23669850 DOI: 10.1364/ao.52.003345] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 03/29/2013] [Indexed: 06/02/2023]
Abstract
Based on the nature of self-mixing signals, we propose the use of the multiple signal classification (MUSIC) algorithm in place of the fast Fourier transform (FFT) for processing signals obtained from self-mixing interferometry (SMI). We apply this algorithm to two representative SMI measurement techniques: range finding and velocimetry. Applying MUSIC to SMI range finding, we find its signal-to-noise ratio performance to be significantly better than that of the FFT, allowing for more robust, longer-range measurement systems. We further demonstrate that MUSIC enables a fundamental change in how SMI Doppler velocity measurement is approached, letting one discard the complex fitting procedure and allowing for a real-time frequency estimation process.
Collapse
Affiliation(s)
- Milan Nikolić
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | | | | | | | | |
Collapse
|
43
|
Bakar AAA, Lim YL, Wilson SJ, Fuentes M, Bertling K, Taimre T, Bosch T, Rakić AD. On the feasibility of self-mixing interferometer sensing for detection of the surface electrocardiographic signal using a customized electro-optic phase modulator. Physiol Meas 2013; 34:281-9. [DOI: 10.1088/0967-3334/34/2/281] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
44
|
Abstract
Self-mixing laser sensors require few components and can be used to measure velocity. The self-mixing laser sensor consists of a laser emitting a beam focused onto a rough target that scatters the beam with some of the emission re-entering the laser cavity. This 'self-mixing' causes measurable interferometric modulation of the laser output power that leads to a periodic Doppler signal spectrum with a peak at a frequency proportional to the velocity of the target. Scattering of the laser emission from a rough surface also leads to a speckle effect that modulates the Doppler signal causing broadening of the signal spectrum adding uncertainty to the velocity measurement. This article analyzes the speckle effect to provide an analytic equation to predict the spectral broadening of an acquired self-mixing signal and compares the predicted broadening to experimental results. To the best of our knowledge, the model proposed in this article is the first model that has successfully predicted speckle broadening in a self-mixing velocimetry sensor in a quantitative manner. It was found that the beam spot size on the target and the target speed affect the resulting spectral broadening caused by speckle. It was also found that the broadening is only weakly dependent on target angle. The experimental broadening was consistently greater than the theoretical speckle broadening due to other effects that also contribute to the total broadening.
Collapse
Affiliation(s)
- Russell Kliese
- The University of Queensland, School of Information Technology and Electrical Engineering, Brisbane, QLD 4072, Australia
| | | |
Collapse
|
45
|
Matharu RS, Perchoux J, Kliese R, Lim YL, Rakić AD. Maintaining maximum signal-to-noise ratio in uncooled vertical-cavity surface-emitting laser-based self-mixing sensors. Opt Lett 2011; 36:3690-3692. [PMID: 21931434 DOI: 10.1364/ol.36.003690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate a method for maintaining the maximum signal-to-noise ratio (SNR) of the signal obtained from the self-mixing sensor based on a vertical-cavity surface-emitting laser (VCSEL). It was found that the locus of the maximum SNR in the current-temperature space can be well approximated by a simple analytical model related to the temperature behavior of the VCSEL threshold current. The optimum sensor performance is achieved by tuning the laser current according to the proposed model, thus enabling the sensor to operate without temperature stabilization in a wide temperature range between -20 °C and +80 °C.
Collapse
Affiliation(s)
- Ranveer S Matharu
- The University of Queensland, School of Information Technology and Electrical Engineering, Brisbane, QLD, Australia
| | | | | | | | | |
Collapse
|
46
|
Dean P, Lim YL, Valavanis A, Kliese R, Nikolić M, Khanna SP, Lachab M, Indjin D, Ikonić Z, Harrison P, Rakić AD, Linfield EH, Davies AG. Terahertz imaging through self-mixing in a quantum cascade laser. Opt Lett 2011; 36:2587-2589. [PMID: 21725488 DOI: 10.1364/ol.36.002587] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect of self-mixing in the THz QCL, and, specifically, by monitoring perturbations to the voltage across the QCL, induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures.
Collapse
Affiliation(s)
- Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Lim YL, Kliese R, Bertling K, Tanimizu K, Jacobs PA, Rakić AD. Self-mixing flow sensor using a monolithic VCSEL array with parallel readout. Opt Express 2010; 18:11720-11727. [PMID: 20589032 DOI: 10.1364/oe.18.011720] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The self-mixing sensing technique is a compact, interferometric sensing technique that can be used for measuring fluid flows. In this work, we demonstrate a parallel readout self-mixing flow velocity sensing system based on a monolithic Vertical-Cavity Surface-Emitting Laser (VCSEL) array. The parallel sensing scheme enables high-resolution full-field imaging systems employing electronic scanning with faster acquisition rates than mechanical scanning systems. The self-mixing signal is acquired from the variation in VCSEL junction voltage, thus markedly reducing the system complexity. The system was validated by measuring velocity distribution of fluid in a custom built diverging-converging planar flow channel. The results obtained agree well with simulation and demonstrate the feasibility of high frame-rate and resolution parallel self-mixing sensors.
Collapse
Affiliation(s)
- Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
| | | | | | | | | | | |
Collapse
|
48
|
Abstract
The self-mixing (SM) laser sensing technique allows for a simple, self-aligned, and robust system for measuring velocity. Low-cost blue emitting GaN laser diodes have recently become available owing to the high volume requirements for Blu-ray Disc devices such as high-definition video players and gaming consoles. These GaN lasers have a significantly shorter wavelength (around 405 nm) compared with other semiconductor lasers (generally around 800 nm for SM sensors). Therefore, if used in SM flow sensors, they allow measuring of flow rates that would otherwise be too slow to measure. In this Letter we report what we believe to be the world's first SM flow measurement system based on a blue emitting semiconductor laser, demonstrating the ability to measure flow rates down to 26 microm/s.
Collapse
Affiliation(s)
- Russell Kliese
- The University of Queensland, School of Information Technology and Electrical Engineering, Queensland 4072, Australia
| | | | | | | |
Collapse
|
49
|
Lu AW, Rakić AD. Design of microcavity organic light emitting diodes with optimized electrical and optical performance. Appl Opt 2009; 48:2282-2289. [PMID: 19381179 DOI: 10.1364/ao.48.002282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A multivariable and multiobjective organic light emitting diode (OLED) design and optimization procedure is presented that produces a microcavity OLED with optimal optical and electrical characteristics. We propose here a design procedure that splits the design process into two design stages where each stage can be optimized independently. In the first stage we design the OLED with optimal electrical and optical performance, where the mirrors are specified by their optimal spectral reflectivity, transmissivity, absorptance, and the phase shift on reflection. In the second stage we synthesize the top and the bottom multilayer mirrors with a minimal number of layers that satisfy the required optimal spectral dependencies determined in the first part of the design process. As a case study we present an optimized design for a top-emitting OLED with a simple bilayered cavity consisting of N, N'-di(naphthalene-1-yl)-N, N'-diphenylbenzidine (NPB) as the hole transport layer and tris(8-hydroxyquinoline)aluminium (Alq3) as the electron transport layer. Conventional devices with an ITO-LiF/Al electrode pair and a Ag?Ag electrode pair are used as reference devices to benchmark the performance of our design. Electrical simulations using the drift-diffusion model and optical simulations employing the integrated dipole antenna approach are implemented to test the performance of the devices. The optimized device shows improved optical and electrical performance when compared with the reference devices.
Collapse
Affiliation(s)
- Albert W Lu
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | | |
Collapse
|
50
|
Lim YL, Nikolic M, Bertling K, Kliese R, Rakić AD. Self-mixing imaging sensor using a monolithic VCSEL array with parallel readout. Opt Express 2009; 17:5517-5525. [PMID: 19333319 DOI: 10.1364/oe.17.005517] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The advent of two-dimensional arrays of Vertical-Cavity Surface-Emitting Lasers (VCSELs) opened a range of potential sensing applications for nanotechnology and life-sciences. With each laser independently addressable, there is scope for the development of high-resolution full-field imaging systems with electronic scanning. We report on the first implementation of a self-mixing imaging system with parallel readout based on a monolithic VCSEL array. A self-mixing Doppler signal was acquired from the variation in VCSEL junction voltage rather than from a conventional variation in laser power, thus markedly reducing the system complexity. The sensor was validated by imaging the velocity distribution on the surface of a rotating disc. The results obtained demonstrate that monolithic arrays of Vertical-Cavity lasers present a powerful tool for the advancement of self-mixing sensors into parallel imaging paradigms and provide a stepping stone to the implementation of a full-field self-mixing sensor systems.
Collapse
Affiliation(s)
- Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, Australia
| | | | | | | | | |
Collapse
|