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Kim AD, McGovern DJ, Williams BS. Multi-bounce self-mixing in terahertz metasurface external-cavity lasers. OPTICS EXPRESS 2024; 32:18880-18895. [PMID: 38859035 DOI: 10.1364/oe.523012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Accepted: 04/29/2024] [Indexed: 06/12/2024]
Abstract
The effects of optical feedback on a terahertz (THz) quantum-cascade metasurface vertical-external-cavity surface-emitting laser (QC-VECSEL) are investigated via self-mixing. A single-mode 2.80 THz QC-VECSEL operating in continuous-wave is subjected to various optical feedback conditions (i.e., feedback strength, round-trip time, and angular misalignment) while variations in its terminal voltage associated with self-mixing are monitored. Due to its large radiating aperture and near-Gaussian beam shape, we find that the QC-VECSEL is strongly susceptible to optical feedback, which is robust against misalignment of external optics. This, in addition to the use of a high-reflectance flat output coupler, results in high feedback levels associated with multiple round-trips within the external cavity-a phenomenon not typically observed for ridge-waveguide QC-lasers. Thus, a new theoretical model is established to describe self-mixing in the QC-VECSEL. The stability of the device under variable optical feedback conditions is also studied. Any mechanical instabilities of the external cavity (such as vibrations of the output coupler), are enhanced due to feedback and result in low-frequency oscillations of the terminal voltage. The work reveals how the self-mixing response differs for the QC-VECSEL architecture, informs other systems in which optical feedback is unavoidable, and paves the way for QC-VECSEL self-mixing applications.
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2
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Teng CC, Westberg J, Wysocki G. Gapless tuning of quantum cascade laser frequency combs with external cavity optical feedback. OPTICS LETTERS 2023; 48:363-366. [PMID: 36638458 DOI: 10.1364/ol.478950] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/09/2022] [Indexed: 06/17/2023]
Abstract
We present the operation of quantum cascade laser frequency combs in an external cavity configuration. Experimental observations show dependence of comb repetition rate and optical spectrum on the external cavity length. The low phase-noise comb regime is extended to a broader range of bias currents, enabling gapless frequency tuning of the comb modes. Dual-comb measurements also confirm improved comb stability in the presence of unwanted optical feedback when operating in an external cavity configuration. These observations indicate that aside from the continuing efforts to assure low and uniform dispersion characteristics of quantum cascade laser frequency combs, the proposed simple approach of adding a broadband external cavity can significantly enhance operation of sub-optimal devices for spectroscopic applications.
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Bertling K, Qi X, Taimre T, Lim YL, Rakić AD. Feedback Regimes of LFI Sensors: Experimental Investigations. SENSORS (BASEL, SWITZERLAND) 2022; 22:9001. [PMID: 36433597 PMCID: PMC9696093 DOI: 10.3390/s22229001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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.
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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
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4
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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, SWITZERLAND) 2022; 22:8501. [PMID: 36366193 PMCID: PMC9658095 DOI: 10.3390/s22218501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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.
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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
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5
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Pistore V, Pogna EAA, Viti L, Li L, Davies AG, Linfield EH, Vitiello MS. Self-Induced Phase Locking of Terahertz Frequency Combs in a Phase-Sensitive Hyperspectral Near-Field Nanoscope. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2200410. [PMID: 35711084 PMCID: PMC9534969 DOI: 10.1002/advs.202200410] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/04/2022] [Indexed: 06/15/2023]
Abstract
Chip-scale, electrically-pumped terahertz (THz) frequency-combs (FCs) rely on nonlinear four-wave-mixing processes, and have a nontrivial phase relationship between the evenly spaced set of emitted modes. Simultaneous monitoring and manipulation of the intermode phase coherence, without any external seeding or active modulation, is a very demanding task for which there has hitherto been no technological solution. Here, a self-mixing intermode-beatnote spectroscopy system is demonstrated, based on THz quantum cascade laser FCs, in which light is back-scattered from the tip of a scanning near-field optical-microscope (SNOM) and the intracavity reinjection monitored. This enables to exploit the sensitivity of FC phase-coherence to optical feedback and, for the first time, manipulate the amplitude, linewidth and frequency of the intermode THz FC beatnote using the feedback itself. Stable phase-locked regimes are used to construct a FC-based hyperspectral, THz s-SNOM nanoscope. This nanoscope provides 160 nm spatial resolution, coherent detection of multiple phase-locked modes, and mapping of the THz optical response of nanoscale materials up to 3.5 THz, with noise-equivalent-power (NEP) ≈400 pW √Hz-1 . This technique can be applied to the entire infrared range, opening up a new approach to hyper-spectral near-field imaging with wide-scale applications in the study of plasmonics and quantum science, inter alia.
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Affiliation(s)
- Valentino Pistore
- NESTCNR‐Istituto Nanoscienze and Scuola Normale SuperiorePisa5612Italy
| | | | - Leonardo Viti
- NESTCNR‐Istituto Nanoscienze and Scuola Normale SuperiorePisa5612Italy
| | - Lianhe Li
- School of Electronic and Electrical EngineeringUniversity of LeedsLeedsLS2 9JTUK
| | - A. Giles Davies
- School of Electronic and Electrical EngineeringUniversity of LeedsLeedsLS2 9JTUK
| | - Edmund H. Linfield
- School of Electronic and Electrical EngineeringUniversity of LeedsLeedsLS2 9JTUK
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6
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Liao X, Wang X, Zhou K, Guan W, Li Z, Ma X, Wang C, Cao JC, Wang C, Li H. Terahertz quantum cascade laser frequency combs with optical feedback. OPTICS EXPRESS 2022; 30:35937-35950. [PMID: 36258533 DOI: 10.1364/oe.467992] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 08/26/2022] [Indexed: 06/16/2023]
Abstract
Optical feedback exists in most laser configurations and strongly affects laser performances depending on the feedback strength, length, and phase. In this paper, we investigate the frequency comb behaviour of a semiconductor quantum cascade laser emitting around 4.2 THz with external optical feedback. A periodic evolution of the laser inter-mode beatnote from single-line to multiple-line structures is experimentally observed with a minor change of optical feedback length (phase) on the wavelength scale. The comb stability of the laser with feedback is also measured and compared with the same laser without feedback. Furthermore, our simulations reveal that the dynamical oscillations invoked by optical feedback are responsible for the measured multiple-line beatnotes. It is found that the characteristic feedback period is determined by the half wavelength of the laser, while the comb operation is maintained at most feedback length positions. Therefore, terahertz quantum cascade laser combs are robust against the minor position vibration of the feedback mirror in practice, owing to the much smaller feedback phase change than that of common near-infrared laser diodes.
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7
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Zhao BB, Wang XG, Wang C. Low-Frequency Oscillations in Quantum Cascade Lasers With Tilted Optical Feedback. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS 2022; 28:1-7. [DOI: 10.1109/jstqe.2021.3091186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Affiliation(s)
- Bin-Bin Zhao
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xing-Guang Wang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Cheng Wang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
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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. OPTICS 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] [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.
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Zhou XY, Wang XG, Zhao BB, Liao QF, Wang C. Frequency noise reduction of delay-coupled quantum cascade lasers. OPTICS EXPRESS 2021; 29:9030-9042. [PMID: 33820341 DOI: 10.1364/oe.415997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 02/25/2021] [Indexed: 06/12/2023]
Abstract
This work theoretically investigates the frequency noise and spectral linewidth characteristics of mutually delay-coupled quantum cascade lasers, which are operated in the stable locking regime. We demonstrate that the mutual injection significantly reduces the frequency noise at proper coupling phases. However, the relative intensity noise is insensitive to the mutual injection. Influences of the pump current, the linewidth broadening factor, the coupling phase, and the delay time on the frequency noise are discussed as well. In addition, it is found that the appearance of multiple compound laser modes can deteriorate the frequency noise performance of the lasers.
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10
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Versatile Multimodality Imaging System Based on Detectorless and Scanless Optical Feedback Interferometry-A Retrospective Overview for A Prospective Vision. SENSORS 2020; 20:s20205930. [PMID: 33092265 PMCID: PMC7589569 DOI: 10.3390/s20205930] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 10/15/2020] [Accepted: 10/17/2020] [Indexed: 11/25/2022]
Abstract
In this retrospective compendium, we attempt to draw a “fil rouge” along fifteen years of our research in the field of optical feedback interferometry aimed at guiding the readers to the verge of new developments in the field. The general reader will be moved at appreciating the versatility and the still largely uncovered potential of the optical feedback interferometry, for both sensing and imaging applications. By discovering the broad range of available wavelengths (0.4–120 μm), the different types of suitable semiconductor lasers (Fabry–Perot, distributed feedback, vertical-cavity, quantum-cascade), and a number of unconventional tenders in multi-axis displacement, ablation front progression, self-referenced measurements, multispectral, structured light feedback imaging and compressive sensing, the specialist also could find inspirational suggestions to expand his field of research.
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11
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Wang XG, Zhao BB, Deng Y, Wang C. Destabilization of Quantum Cascade Lasers Using Tilted Optical Feedback. 2020 IEEE PHOTONICS CONFERENCE (IPC) 2020. [DOI: 10.1109/ipc47351.2020.9252389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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12
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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. OPTICS 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] [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.
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13
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Wang XG, Zhao BB, Grillot F, Wang C. Spectral linewidth reduction of quantum cascade lasers by strong optical feedback. JOURNAL OF APPLIED PHYSICS 2020; 127. [DOI: 10.1063/1.5124521] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
In this work, we propose to employ strong optical feedback to narrow the spectral linewidth of quantum cascade lasers without using any phase control. Rate equation analysis demonstrates that optical feedback beyond a certain level always reduces the laser linewidth for any feedback phase. It is also found that the linewidth becomes less sensitive to the feedback phase for higher feedback strength. Simulations show that optical feedback with a feedback ratio of −10 dB can suppress the laser linewidth by about two orders of magnitude. This is in contrast to near-infrared laser diodes, which can be easily destabilized by strong feedback.
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Affiliation(s)
- Xing-Guang Wang
- School of Information Science and Technology, ShanghaiTech University 1 , Shanghai 201210, China
- Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences 2 , Shanghai 200050, China
- University of Chinese Academy of Sciences 3 , Beijing 100049, China
| | - Bin-Bin Zhao
- School of Information Science and Technology, ShanghaiTech University 1 , Shanghai 201210, China
- Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences 2 , Shanghai 200050, China
- University of Chinese Academy of Sciences 3 , Beijing 100049, China
| | - Frédéric Grillot
- LTCI, Télécom Paris, Institut Polytechnique de Paris 4 , 46 Rue Barrault, 75013 Paris, France
| | - Cheng Wang
- School of Information Science and Technology, ShanghaiTech University 1 , Shanghai 201210, China
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Ottomaniello A, Keeley J, Rubino P, Li L, Cecchini M, Linfield EH, Davies AG, Dean P, Pitanti A, Tredicucci A. Optomechanical response with nanometer resolution in the self-mixing signal of a terahertz quantum cascade laser. OPTICS LETTERS 2019; 44:5663-5666. [PMID: 31774748 DOI: 10.1364/ol.44.005663] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Owing to their intrinsic stability against optical feedback (OF), quantum cascade lasers (QCLs) represent a uniquely versatile source to further improve self-mixing interferometry at mid-infrared and terahertz (THz) frequencies. Here, we show the feasibility of detecting with nanometer precision, the deeply subwavelength ($ \lt \lambda /6000 $<λ/6000) mechanical vibrations of a suspended $ {{\rm Si}_3}{{\rm N}_4} $Si3N4 membrane used as the external element of a THz QCL feedback interferometer. Besides representing an extension of the applicability of vibrometric characterization at THz frequencies, our system can be exploited for the realization of optomechanical applications, such as dynamical switching between different OF regimes and a still-lacking THz master-slave configuration.
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15
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Zhao BB, Kovanis V, Wang C. Tunable Frequency Comb Generation Using Quantum Cascade Lasers Subject to Optical Injection. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS 2019; 25:1-7. [DOI: 10.1109/jstqe.2019.2919803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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16
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Zhao BB, Wang XG, Zhang J, Wang C. Relative intensity noise of a mid-infrared quantum cascade laser: insensitivity to optical feedback. OPTICS EXPRESS 2019; 27:26639-26647. [PMID: 31674540 DOI: 10.1364/oe.27.026639] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 07/16/2019] [Indexed: 06/10/2023]
Abstract
This article experimentally demonstrates that the relative intensity noise (RIN) of a mid-infrared quantum cascade laser is insensitive to the optical feedback for feedback ratios up to 31% (-5.1 dB). The RIN of the free-running laser is in the range of -150 dB/Hz to -160 dB/Hz, while the optical feedback induced RIN variation is less than ± 2.0 dB. In addition, the feedback-induced lasing frequency variation is less than 2.0 GHz. Rate equation analyses of the laser are in good agreement with the experimental observations.
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17
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Li Y, Chu W, Yang N, Ge L, Xie Y, Zhang W, Duan S, Wang Y, Sun J. Optically mutual-injected terahertz quantum cascade lasers for self-mixing velocity measurements. OPTICS EXPRESS 2019; 27:27076-27087. [PMID: 31674575 DOI: 10.1364/oe.27.027076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 08/16/2019] [Indexed: 06/10/2023]
Abstract
Self-mixing velocity sensor based on a mutual-injected two-element terahertz quantum cascade laser (THz QCL) array is studied theoretically. The working characteristics of mutual-injected THz QCL array with different frequency detunings and self-mixing feedback strengths, as well as their influences on the self-mixing measurements are discussed in detail. Within the phase-locked range, each laser in the array reaches a stable state rapidly and can be used as a self-mixing detector due to the mutual injection coupling. The array will no longer be phase-locked when the frequency detuning of the lasers is too large, and only the laser that receives the feedback light can still be used for self-mixing velocity measurements. It is also found that even for the case of strong feedback, the THz QCLs will not be completely unstable and the self-mixing velocity measurements could also be possible. In addition, the simulation also shows that the array could measure two independent moving targets simultaneously. These results provide the theoretical support for the future applications of THz QCL arrays in self-mixing sensors.
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Wang XG, Zhao BB, Wang C. Optical Feedback Effects on the Relative Intensity Noise of a Mid-Infrared Quantum Cascade Laser. 2019 IEEE PHOTONICS CONFERENCE (IPC) 2019. [DOI: 10.1109/ipcon.2019.8908436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Mezzapesa FP, Pistore V, Garrasi K, Li L, Davies AG, Linfield EH, Dhillon S, Vitiello MS. Tunable and compact dispersion compensation of broadband THz quantum cascade laser frequency combs. OPTICS EXPRESS 2019; 27:20231-20240. [PMID: 31510121 DOI: 10.1364/oe.27.020231] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 06/04/2019] [Indexed: 05/20/2023]
Abstract
Miniaturized frequency combs (FCs) can be self-generated at terahertz (THz) frequencies through four-wave mixing in the cavity of a quantum cascade laser (QCL). To date, however, stable comb operation is only observed over a small operational current range in which the bias-depended chromatic dispersion is compensated. As most dispersion compensation techniques in the THz range are not tunable, this limits the spectral coverage of the comb and the emitted output power, restricting potential applications in, for example, metrology and ultrashort THz pulse generation. Here, we demonstrate an alternative architecture that provides a tunable, lithographically independent, control of the free-running coherence properties of THz QCL FCs. This is achieved by integrating an on-chip tightly coupled mirror with the QCL cavity, providing an external cavity and hence a tunable Gires Tournois interferometer (GTI). By finely adjusting the gap between the GTI and the back-facet of an ultra-broadband, high dynamic range QCL, we attain wide dispersion compensation regions, where stable and narrow (~3 kHz linewidth) single beatnotes extend over an operation range that is significantly larger than that of dispersion-dominated bare laser cavity counterparts. Significant reduction of the phase noise is registered over the whole QCL spectral bandwidth (1.35 THz). This agile accommodation of a tunable dispersion compensator will help enable uptake of QCL-combs for metrological, spectroscopic and quantum technology-oriented applications.
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Nguimdo RM, Erneux T. Enhanced performances of a photonic reservoir computer based on a single delayed quantum cascade laser. OPTICS LETTERS 2019; 44:49-52. [PMID: 30645545 DOI: 10.1364/ol.44.000049] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 11/06/2018] [Indexed: 06/09/2023]
Abstract
In previous works, it has been shown that reservoir computing (RC) systems using a laser subject to a delayed optical feedback and stabilized by an injected signal may be highly sensitive to the feedback phase. In this Letter, we show that a RC system using a single quantum cascade laser subject to a delayed optical feedback but without injection is robust to the feedback phase for a large range of values of the parameters.
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Mičica M, Eliet S, Vanwolleghem M, Motiyenko R, Pienkina A, Margulès L, Postava K, Pištora J, Lampin JF. High-resolution THz gain measurements in optically pumped ammonia. OPTICS EXPRESS 2018; 26:21242-21248. [PMID: 30119428 DOI: 10.1364/oe.26.021242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 04/18/2018] [Indexed: 06/08/2023]
Abstract
This study is aimed at the evaluation of THz gain properties in an optically pumped NH3 gas. NH3 molecules undergo rotational-vibrational excitation by mid-infrared (MIR) optical pumping provided by a MIR quantum cascade laser (QCL) which enables precise tuning to the NH3 infrared transition around 10.3 μm. Pure inversion transitions, (J = 3, K = 3) at 1.073 THz and (J = 4, K = 4) at 1.083 THz were selected. The THz measurements were performed using a THz frequency multiplier chain. The results show line profiles with and without optical pumping at different NH3 pressures, and with different MIR tuning. The highest gain at room temperature under the best conditions obtained during single pass on the (3,3) line was 10.1 dB×m-1 at 26 μbar with a pumping power of 40 mW. The (4,4) line showed lower gain of 6.4 dB×m-1 at 34 μbar with a pumping power of 62 mW. To our knowledge these THz gains are the highest measured in a continuous-wave MIR pumped gas.
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22
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Giordano MC, Mastel S, Liewald C, Columbo LL, Brambilla M, Viti L, Politano A, Zhang K, Li L, Davies AG, Linfield EH, Hillenbrand R, Keilmann F, Scamarcio G, Vitiello MS. Phase-resolved terahertz self-detection near-field microscopy. OPTICS EXPRESS 2018; 26:18423-18435. [PMID: 30114022 DOI: 10.1364/oe.26.018423] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 05/30/2018] [Indexed: 06/08/2023]
Abstract
At terahertz (THz) frequencies, scattering-type scanning near-field optical microscopy (s-SNOM) based on continuous wave sources mostly relies on cryogenic and bulky detectors, which represents a major constraint for its practical application. Here, we devise a THz s-SNOM system that provides both amplitude and phase contrast and achieves nanoscale (60-70nm) in-plane spatial resolution. It features a quantum cascade laser that simultaneously emits THz frequency light and senses the backscattered optical field through a voltage modulation induced inherently through the self-mixing technique. We demonstrate its performance by probing a phonon-polariton-resonant CsBr crystal and doped black phosphorus flakes.
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23
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Weicker L, Wolfersberger D, Sciamanna M. Stability analysis of a quantum cascade laser subject to phase-conjugate feedback. Phys Rev E 2018; 98:012214. [PMID: 30110868 DOI: 10.1103/physreve.98.012214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Indexed: 06/08/2023]
Abstract
We investigate the stability boundaries of a quantum cascade laser subject to phase-conjugate optical feedback. From a three-level model, we reduce our set of equations to the usual modified Lang-Kobayashi equations describing a semiconductor laser subject to phase-conjugate feedback. We then determine the Hopf bifurcation conditions, which we explore by using asymptotic methods. In the limit of large delays, we find approximations of the first Hopf bifurcation that is responsible for the destabilization of the system. We obtain an expression that depends only on three parameters: the feedback strength, the line-width enhancement factor, and the pump current. From this expression, we study the stability boundaries of our system. We compare our results with the initial three-level model using a continuation method. We find qualitative and quantitative agreements of the stability boundaries with the two methods. Finally, we compare our findings with the ones obtained for a quantum cascade laser subject to conventional optical feedback.
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Affiliation(s)
- Lionel Weicker
- Chair in Photonics, LMOPS, CentraleSupélec, Université Paris-Saclay, F-57070 Metz, France and Chair in Photonics, LMOPS, CentraleSupélec, Université de Lorraine, F-57070 Metz, France
| | - Delphine Wolfersberger
- Chair in Photonics, LMOPS, CentraleSupélec, Université Paris-Saclay, F-57070 Metz, France and Chair in Photonics, LMOPS, CentraleSupélec, Université de Lorraine, F-57070 Metz, France
| | - Marc Sciamanna
- Chair in Photonics, LMOPS, CentraleSupélec, Université Paris-Saclay, F-57070 Metz, France and Chair in Photonics, LMOPS, CentraleSupélec, Université de Lorraine, F-57070 Metz, France
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24
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Davis CM, Reddish MJ, Dyer RB. Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 178:185-191. [PMID: 28189834 PMCID: PMC5346054 DOI: 10.1016/j.saa.2017.01.069] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 01/27/2017] [Accepted: 01/31/2017] [Indexed: 05/30/2023]
Abstract
Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of <0.2mOD and a fluorescence sensitivity of 2% of the overall fluorescence intensity. Using a computer controlled QCL to rapidly tune the IR frequency it is possible to create a T-jump induced difference spectrum from 50ns to 0.5ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics.
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Affiliation(s)
- Caitlin M Davis
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
| | - Michael J Reddish
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
| | - R Brian Dyer
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States.
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25
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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. OPTICS 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] [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.
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26
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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. OPTICS 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] [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.
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27
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Friart G, Van der Sande G, Verschaffelt G, Erneux T. Analytical stability boundaries for quantum cascade lasers subject to optical feedback. Phys Rev E 2016; 93:052201. [PMID: 27300874 DOI: 10.1103/physreve.93.052201] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Indexed: 11/07/2022]
Abstract
We consider nonlinear rate equations appropriate for a quantum cascade laser subject to optical feedback. We analyze the conditions for a Hopf bifurcation in the limit of large values of the delay. We obtain a simple expression for the critical feedback rate that highlights the effects of key parameters such as the linewidth enhancement factor and the pump. All our asymptotic approximations are validated numerically by using a path continuation technique that allows us to follow Hopf bifurcation points in parameter space.
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Affiliation(s)
- Gaetan Friart
- Université libre de Bruxelles, Optique Nonlinéaire Théorique, Campus Plaine, C.P. 231, 1050 Bruxelles, Belgium
| | - Guy Van der Sande
- Vrije Universiteit Brussel, Applied Physics Research Group (APHY), Pleinlaan 2, 1050 Brussel, Belgium
| | - Guy Verschaffelt
- Vrije Universiteit Brussel, Applied Physics Research Group (APHY), Pleinlaan 2, 1050 Brussel, Belgium
| | - Thomas Erneux
- Université libre de Bruxelles, Optique Nonlinéaire Théorique, Campus Plaine, C.P. 231, 1050 Bruxelles, Belgium
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28
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Jumpertz L, Schires K, Carras M, Sciamanna M, Grillot F. Chaotic light at mid-infrared wavelength. LIGHT, SCIENCE & APPLICATIONS 2016; 5:e16088. [PMID: 30167171 PMCID: PMC6059957 DOI: 10.1038/lsa.2016.88] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 01/27/2016] [Accepted: 01/27/2016] [Indexed: 06/06/2023]
Abstract
The onset of nonlinear dynamics and chaos is evidenced in a mid-infrared distributed feedback quantum cascade laser both in the temporal and frequency domains. As opposed to the commonly observed route to chaos in semiconductor lasers, which involves undamping of the laser relaxation oscillations, quantum cascade lasers first exhibit regular self-pulsation at the external cavity frequency before entering into a chaotic low-frequency fluctuation regime. The bifurcation sequence, similar to that already observed in class A gas lasers under optical feedback, results from the fast carrier relaxation dynamics occurring in quantum cascade lasers, as confirmed by numerical simulations. Such chaotic behavior can impact various practical applications including spectroscopy, which requires stable single-mode operation. It also allows the development of novel mid-infrared high-power chaotic light sources, thus enabling secure free-space high bit-rate optical communications based on chaos synchronization.
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Affiliation(s)
- Louise Jumpertz
- CNRS LTCI, Télécom ParisTech, Université Paris Saclay, 75634 Paris Cedex 13, France
- mirSense, 86 rue de Paris, bat. Erable, 91400 Orsay, France
| | - Kevin Schires
- CNRS LTCI, Télécom ParisTech, Université Paris Saclay, 75634 Paris Cedex 13, France
| | - Mathieu Carras
- mirSense, 86 rue de Paris, bat. Erable, 91400 Orsay, France
| | - Marc Sciamanna
- LMOPS (Laboratoire Matériaux Optiques, Photonique et Systèmes), CentraleSupélec, Université Paris Saclay, 57070 Metz, France
- LMOPS (Laboratoire Matériaux Optiques, Photonique et Systèmes), CentraleSupélec, Université de Lorraine, 57070 Metz, France
| | - Frédéric Grillot
- CNRS LTCI, Télécom ParisTech, Université Paris Saclay, 75634 Paris Cedex 13, France
- Center for High Technology Materials, University of New-Mexico, Albuquerque, 87106-4343 NM, USA
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29
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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, SWITZERLAND) 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] [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.
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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.
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30
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Grillot F, Jumpertz L, Schires K, Carras M, Sciamanna M. Deterministic temporal chaos from a mid-infrared external cavity quantum cascade lasers. ACTA ACUST UNITED AC 2016. [DOI: 10.1117/12.2213434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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31
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Photo-generated metamaterials induce modulation of CW terahertz quantum cascade lasers. Sci Rep 2015; 5:16207. [PMID: 26549166 PMCID: PMC4637892 DOI: 10.1038/srep16207] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 09/17/2015] [Indexed: 11/09/2022] Open
Abstract
Periodic patterns of photo-excited carriers on a semiconductor surface profoundly modifies its effective permittivity, creating a stationary all-optical quasi-metallic metamaterial. Intriguingly, one can tailor its artificial birefringence to modulate with unprecedented degrees of freedom both the amplitude and phase of a quantum cascade laser (QCL) subject to optical feedback from such an anisotropic reflector. Here, we conceive and devise a reconfigurable photo-designed Terahertz (THz) modulator and exploit it in a proof-of-concept experiment to control the emission properties of THz QCLs. Photo-exciting sub-wavelength metastructures on silicon, we induce polarization-dependent changes in the intra-cavity THz field, that can be probed by monitoring the voltage across the QCL terminals. This inherently flexible approach promises groundbreaking impact on THz photonics applications, including THz phase modulators, fast switches, and active hyperbolic media.
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32
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Study of QCL Laser Sources for the Realization of Advanced Sensors. SENSORS 2015; 15:19140-56. [PMID: 26251907 PMCID: PMC4570363 DOI: 10.3390/s150819140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/22/2015] [Accepted: 07/27/2015] [Indexed: 11/20/2022]
Abstract
We study the nonlinear dynamics of a quantum cascade laser (QCL) with a strong reinjection provided by the feedback from two external targets in a double cavity configuration. The nonlinear coupling of interferometric signals from the two targets allows us to propose a displacement sensor with nanometric resolution. The system exploits the ultra-stability of QCLs in self-mixing configuration to access the intrinsic nonlinearity of the laser, described by the Lang–Kobayashi model, and it relies on a stroboscopic-like effect in the voltage signal registered at the QCL terminals that relates the “slow” target motion to the “fast” target one.
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33
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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. OPTICS LETTERS 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] [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.
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34
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Wienold M, Röben B, Schrottke L, Grahn HT. Evidence for frequency comb emission from a Fabry-Pérot terahertz quantum-cascade laser. OPTICS EXPRESS 2014; 22:30410-30424. [PMID: 25606987 DOI: 10.1364/oe.22.030410] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on a broad-band terahertz quantum-cascade laser (QCL) with a long Fabry-Pérot ridge cavity, for which the tuning range of the individual laser modes exceeds the mode spacing. While a spectral range of approximately 60 GHz (2 cm(-1)) is continuously covered by current and temperature tuning, the total emission range spans more than 270 GHz (9 cm(-1)). Within certain operating ranges, we found evidence for stable frequency comb operation of the QCL. An experimental technique is presented to characterize frequency comb operation, which is based on the self-mixing effect.
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35
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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. OPTICS 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] [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.
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36
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Columbo LL, Brambilla M. Multimode regimes in quantum cascade lasers with optical feedback. OPTICS EXPRESS 2014; 22:10105-10118. [PMID: 24921716 DOI: 10.1364/oe.22.010105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study the instability thresholds of the stationary emission of a quantum cascade laser with optical feedback described by the Lang Kobayashi model. We introduce an exact linear stability analysis and an approximated one for an unipolar lasers, who does not exhibit relaxation oscillations, and investigate the regimes of the emitter beyond the continuous wave instability threshold, depending on the number and density of the external cavity modes. We then show that a unipolar laser with feedback can exhibit coherent multimode oscillations that indicate spontaneous phase-locking.
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37
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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. OPTICS LETTERS 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] [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.
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38
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Mezzapesa FP, Columbo LL, Dabbicco M, Brambilla M, Scamarcio G. QCL-based nonlinear sensing of independent targets dynamics. OPTICS EXPRESS 2014; 22:5867-5874. [PMID: 24663924 DOI: 10.1364/oe.22.005867] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate a common-path interferometer to measure the independent displacement of multiple targets through nonlinear frequency mixing in a quantum-cascade laser (QCL). The sensing system exploits the unique stability of QCLs under strong optical feedback to access the intrinsic nonlinearity of the active medium. The experimental results using an external dual cavity are in excellent agreement with the numerical simulations based on the Lang-Kobayashi equations.
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39
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Erneux T, Kovanis V, Gavrielides A. Nonlinear dynamics of an injected quantum cascade laser. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:032907. [PMID: 24125325 DOI: 10.1103/physreve.88.032907] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Indexed: 06/02/2023]
Abstract
The stability properties of an injected quantum cascade laser are investigated analytically on the basis of current estimates of the laser parameters. We show that in addition to stable locking, Hopf bifurcations leading to pulsating intensities are possible. We discuss the stability diagrams in terms of the detuning and the injection rate for different values of the linewidth enhancement factor. The analysis indicates domains of coexistence between two stable steady states (bistability) or between a stable steady state and stable periodic oscillations. All predictions are verified numerically by determining bifurcation diagrams from the laser rate equations.
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Affiliation(s)
- Thomas Erneux
- Université Libre de Bruxelles, Optique Nonlinéaire Théorique, Campus Plaine, C. P. 231, 1050 Bruxelles, Belgium
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