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Levy S, Gower NL, Piperno S, Addamane SJ, Reno JL, Albo A. Analyzing the effect of doping concentration in split-well resonant-phonon terahertz quantum cascade lasers. OPTICS EXPRESS 2024; 32:12040-12053. [PMID: 38571038 DOI: 10.1364/oe.515419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 02/27/2024] [Indexed: 04/05/2024]
Abstract
The effect of doping concentration on the temperature performance of the novel split-well resonant-phonon (SWRP) terahertz quantum-cascade laser (THz QCL) scheme supporting a clean 4-level system design was analyzed using non-equilibrium Green's functions (NEGF) calculations. Experimental research showed that increasing the doping concentration in these designs led to better results compared to the split-well direct-phonon (SWDP) design, which has a larger overlap between its active laser states and the doping profile. However, further improvement in the temperature performance was expected, which led us to assume there was an increased gain and line broadening when increasing the doping concentration despite the reduced overlap between the doped region and the active laser states. Through simulations based on NEGF calculations we were able to study the contribution of the different scattering mechanisms on the performance of these devices. We concluded that the main mechanism affecting the lasers' temperature performance is electron-electron (e-e) scattering, which largely contributes to gain and line broadening. Interestingly, this scattering mechanism is independent of the doping location, making efforts to reduce overlap between the doped region and the active laser states less effective. Optimization of the e-e scattering thus could be reached only by fine tuning of the doping density in the devices. By uncovering the subtle relationship between doping density and e-e scattering strength, our study not only provides a comprehensive understanding of the underlying physics but also offers a strategic pathway for overcoming current limitations. This work is significant not only for its implications on specific devices but also for its potential to drive advancements in the entire THz QCL field, demonstrating the crucial role of e-e scattering in limiting temperature performance and providing essential knowledge for pushing THz QCLs to new temperature heights.
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Djevahirdjian L, Lechevallier L, Martin-Drumel MA, Pirali O, Ducournau G, Kassi R, Kassi S. Frequency stable and low phase noise THz synthesis for precision spectroscopy. Nat Commun 2023; 14:7162. [PMID: 37935704 PMCID: PMC10630442 DOI: 10.1038/s41467-023-42905-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 10/24/2023] [Indexed: 11/09/2023] Open
Abstract
We present a robust approach to generate a continuously tunable, low phase noise, Hz linewidth and mHz/s stability THz emission in the 0.1 THz to 1.4 THz range. This is achieved by photomixing two commercial telecom, distributed feedback lasers locked by optical-feedback onto a single highly stable V-shaped optical cavity. The phase noise is evaluated up to 1.2 THz, demonstrating Hz-level linewidth. To illustrate the spectral performances and agility of the source, low pressure absorption lines of methanol and water vapors have been recorded up to 1.4 THz. In addition, the hyperfine structure of a water line at 556.9 GHz, obtained by saturation spectroscopy, is also reported, resolving spectral features displaying a full-width at half-maximum of 10 kHz. The present results unambiguously establish the performances of this source for ultra-high resolution molecular physics.
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Affiliation(s)
| | | | | | - Olivier Pirali
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay, France.
| | - Guillaume Ducournau
- Université de Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 IEMN, Institut d'Electronique de Microélectronique et de Nanotechnologie, 59655 Villeneuve d'Ascq, France.
| | - Rédha Kassi
- Université de Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 IEMN, Institut d'Electronique de Microélectronique et de Nanotechnologie, 59655 Villeneuve d'Ascq, France.
| | - Samir Kassi
- Univ. Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
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3
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Ha T, Yoo D, Heo C, Vidal-Codina F, Nguyen NC, Sim KI, Park SH, Cha W, Park S, Peraire J, Kim TT, Lee YH, Oh SH. Subwavelength Terahertz Resonance Imaging (STRING) for Molecular Fingerprinting. NANO LETTERS 2022; 22:10200-10207. [PMID: 36507551 DOI: 10.1021/acs.nanolett.2c04610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Subwavelength terahertz (THz) imaging methods are highly desirable for biochemical sensing as well as materials sciences, yet sensitive spectral fingerprinting is still challenging in the frequency domain due to weak light-matter interactions. Here, we demonstrate subwavelength THz resonance imaging (STRING) that overcomes this limitation to achieve ultrasensitive molecular fingerprinting. STRING combines individual ring-shaped coaxial single resonators with near-field spectroscopy, yielding considerable sensitivity gains from both local field enhancement and the near-field effect. As an initial demonstration, we obtained spectral fingerprints from isomers of α-lactose and maltose monohydrates, achieving sensitivity that was enhanced by up to 10 orders of magnitude compared to far-field THz measurements with pelletized samples. Our results show that the STRING platform could enable the development of THz spectroscopy as a practical and sensitive tool for the fingerprinting and spectral imaging of molecules and nanoparticles.
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Affiliation(s)
- Taewoo Ha
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon16419, Republic of Korea
| | - Daehan Yoo
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota55455, United States
| | - Chaejeong Heo
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon16419, Republic of Korea
- Institute for Quantum Biophysics, Sungkyunkwan University, Suwon16419, Republic of Korea
| | - Ferran Vidal-Codina
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
| | - Ngoc-Cuong Nguyen
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
| | - Kyung Ik Sim
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon16419, Republic of Korea
| | - Sang Hyun Park
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota55455, United States
| | - Wujoon Cha
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon16419, Republic of Korea
| | - Sungsu Park
- School of Mechanical Engineering, Sungkyunkwan University, Suwon16419, Republic of Korea
| | - Jaime Peraire
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
| | - Teun-Teun Kim
- Department of Physics, University of Ulsan, Ulsan44610, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon16419, Republic of Korea
| | - Sang-Hyun Oh
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota55455, United States
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Chevalier P, Piccardo M, Amirzhan A, Capasso F, Everitt HO. Accurately Measuring Molecular Rotational Spectra in Excited Vibrational Modes. APPLIED SPECTROSCOPY 2022; 76:1494-1503. [PMID: 35775457 DOI: 10.1177/00037028221111174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Although gas phase rotational spectroscopy is a mature field for which millions of rotational spectral lines have been measured in hundreds of molecules with sub-MHz accuracy, it remains a challenge to measure these rotational spectra in excited vibrational modes with the same accuracy. Recently, it was demonstrated that virtually any rotational transition in excited vibrational modes of most molecules may be made to lase when pumped by a continuously tunable quantum cascade laser (QCL). Here, we demonstrate how an infrared QCL may be used to enhance absorption strength or induce lasing of terahertz rotational transitions in highly excited vibrational modes in order to measure their frequencies more accurately. To illustrate the concepts, we used a tunable QCL to excite v3 R-branch transitions in N2O and either enhanced absorption or induced lasing on 20 v3 rotational transitions, whose frequencies between 299 and 772 GHz were then measured using either heterodyne or modulation spectroscopy. The spectra were fitted to obtain the rotational constants B3 and D3, which reproduce the measured spectra to within the experimental uncertainty of ± 5 kHz. We then show how this technique may be generalized by estimating the threshold power to make any rotational transition lase in any N2O vibrational mode.
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Affiliation(s)
- Paul Chevalier
- Harvard John A. Paulson School of Engineering and Applied Sciences, 1812Harvard University, Cambridge, MA, USA
| | - Marco Piccardo
- Harvard John A. Paulson School of Engineering and Applied Sciences, 1812Harvard University, Cambridge, MA, USA
- Center for Nano Science and Technology, Fondazione Istituto Italiano di Tecnologia, Milan, Italy
| | - Arman Amirzhan
- Harvard John A. Paulson School of Engineering and Applied Sciences, 1812Harvard University, Cambridge, MA, USA
| | - Federico Capasso
- Harvard John A. Paulson School of Engineering and Applied Sciences, 1812Harvard University, Cambridge, MA, USA
| | - Henry O Everitt
- 1024DEVCOM Army Research Laboratory, Houston, TX, USA
- Department of Physics, 3065Duke University, Durham, NC, USA
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5
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Geng L, Zhang R, Yan P, Qu Y, Ji Z, Zhai Y, Zhao W, Zhang Z, Zhang W, Yang K. Temporal behavior of the high-power pulsed gas terahertz laser pumped by a fundamental mode TEA CO 2 laser. OPTICS EXPRESS 2022; 30:39961-39975. [PMID: 36298937 DOI: 10.1364/oe.470793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 10/02/2022] [Indexed: 06/16/2023]
Abstract
Optically pumped gas molecular terahertz (THz) lasers are promising for generating high-power and high-beam-quality coherent THz radiation. However, for pulsed gas THz lasers, the temporal behavior of the output THz pulse has rarely been investigated. In this study, the temporal behavior of a pulsed gas THz pumped by a fundamental-mode TEA CO2 laser has been presented for the first time both in simulation and experiment. A modified laser kinetics model based on the density matrix rate equation was used to simulate the temporal behavior and output pulse energy of a pulsed gas THz laser at different gas pressures. The results clearly show that the working gas pressure and pump pulse energy have critical influences on the output THz pulse shape. Three typical pulse shapes were obtained, and the THz pulse splitting caused by gain switching was quantitatively simulated and explained based on the laser dynamic process. Besides, with an incident pump pulse energy of 342 mJ, the maximum output THz pulse energy of 2.31 mJ was obtained at 385 µm, which corresponds to a photon conversion efficiency of approximately 56.1%, and to our knowledge, this is the highest efficiency for D2O gas THz laser. The experimental results agreed well with those of the numerical simulation for the entire working gas pressure range, indicating that our model is a powerful tool and paves the way for designing and optimizing high-power pulsed gas lasers.
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Wang W, Lu PK, Vinod AK, Turan D, McMillan JF, Liu H, Yu M, Kwong DL, Jarrahi M, Wong CW. Coherent terahertz radiation with 2.8-octave tunability through chip-scale photomixed microresonator optical parametric oscillation. Nat Commun 2022; 13:5123. [PMID: 36045124 PMCID: PMC9433451 DOI: 10.1038/s41467-022-32739-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 08/12/2022] [Indexed: 12/03/2022] Open
Abstract
High-spectral-purity frequency-agile room-temperature sources in the terahertz spectrum are foundational elements for imaging, sensing, metrology, and communications. Here we present a chip-scale optical parametric oscillator based on an integrated nonlinear microresonator that provides broadly tunable single-frequency and multi-frequency oscillators in the terahertz regime. Through optical-to-terahertz down-conversion using a plasmonic nanoantenna array, coherent terahertz radiation spanning 2.8-octaves is achieved from 330 GHz to 2.3 THz, with ≈20 GHz cavity-mode-limited frequency tuning step and ≈10 MHz intracavity-mode continuous frequency tuning range at each step. By controlling the microresonator intracavity power and pump-resonance detuning, tunable multi-frequency terahertz oscillators are also realized. Furthermore, by stabilizing the microresonator pump power and wavelength, sub-100 Hz linewidth of the terahertz radiation with 10−15 residual frequency instability is demonstrated. The room-temperature generation of both single-frequency, frequency-agile terahertz radiation and multi-frequency terahertz oscillators in the chip-scale platform offers unique capabilities in metrology, sensing, imaging and communications. High-spectral-purity frequency-agile room-temperature THz sources are foundational elements for imaging, sensing, metrology, and communications. Here a parametric oscillator-photomixer chip with coherent 2.8-octave tunable THz radiation is achieved.
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Affiliation(s)
- Wenting Wang
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA.
| | - Ping-Keng Lu
- Terahertz Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Abhinav Kumar Vinod
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Deniz Turan
- Terahertz Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - James F McMillan
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Hao Liu
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Mingbin Yu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Shanghai, China.,Institute of Microelectronics, A*STAR, Singapore, 117865, Singapore
| | - Dim-Lee Kwong
- Institute of Microelectronics, A*STAR, Singapore, 117865, Singapore
| | - Mona Jarrahi
- Terahertz Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA.
| | - Chee Wei Wong
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA.
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7
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Hearne TS, Mammez MH, Mammez D, Martin-Drumel MA, Roy P, Pirali O, Eliet S, Barbieri S, Hindle F, Mouret G, Lampin JF. Unlocking synchrotron sources for THz spectroscopy at sub-MHz resolution. OPTICS EXPRESS 2022; 30:7372-7382. [PMID: 35299501 DOI: 10.1364/oe.448147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 01/15/2022] [Indexed: 06/14/2023]
Abstract
Synchrotron radiation (SR) has proven to be an invaluable contributor to the field of molecular spectroscopy, particularly in the terahertz region (1-10 THz) where its bright and broadband properties are currently unmatched by laboratory sources. However, measurements using SR are currently limited to a resolution of around 30 MHz, due to the limits of Fourier-transform infrared spectroscopy. To push the resolution limit further, we have developed a spectrometer based on heterodyne mixing of SR with a newly available THz molecular laser, which can operate at frequencies ranging from 1 to 5.5 THz. This spectrometer can record at a resolution of 80 kHz, with 5 GHz of bandwidth around each molecular laser frequency, making it the first SR-based instrument capable of sub-MHz, Doppler-limited spectroscopy across this wide range. This allows closely spaced spectral features, such as the effects of internal dynamics and fine angular momentum couplings, to be observed. Furthermore, mixing of the molecular laser with a THz comb is demonstrated, which will enable extremely precise determinations of molecular transition frequencies.
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Cherkasova OP, Serdyukov DS, Nemova EF, Ratushnyak AS, Kucheryavenko AS, Dolganova IN, Xu G, Skorobogatiy M, Reshetov IV, Timashev PS, Spektor IE, Zaytsev KI, Tuchin VV. Cellular effects of terahertz waves. JOURNAL OF BIOMEDICAL OPTICS 2021; 26:JBO-210179VR. [PMID: 34595886 PMCID: PMC8483303 DOI: 10.1117/1.jbo.26.9.090902] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/08/2021] [Indexed: 05/15/2023]
Abstract
SIGNIFICANCE An increasing interest in the area of biological effects at exposure of tissues and cells to the terahertz (THz) radiation is driven by a rapid progress in THz biophotonics, observed during the past decades. Despite the attractiveness of THz technology for medical diagnosis and therapy, there is still quite limited knowledge about safe limits of THz exposure. Different modes of THz exposure of tissues and cells, including continuous-wave versus pulsed radiation, various powers, and number and duration of exposure cycles, ought to be systematically studied. AIM We provide an overview of recent research results in the area of biological effects at exposure of tissues and cells to THz waves. APPROACH We start with a brief overview of general features of the THz-wave-tissue interactions, as well as modern THz emitters, with an emphasis on those that are reliable for studying the biological effects of THz waves. Then, we consider three levels of biological system organization, at which the exposure effects are considered: (i) solutions of biological molecules; (ii) cultures of cells, individual cells, and cell structures; and (iii) entire organs or organisms; special attention is devoted to the cellular level. We distinguish thermal and nonthermal mechanisms of THz-wave-cell interactions and discuss a problem of adequate estimation of the THz biological effects' specificity. The problem of experimental data reproducibility, caused by rareness of the THz experimental setups and an absence of unitary protocols, is also considered. RESULTS The summarized data demonstrate the current stage of the research activity and knowledge about the THz exposure on living objects. CONCLUSIONS This review helps the biomedical optics community to summarize up-to-date knowledge in the area of cell exposure to THz radiation, and paves the ways for the development of THz safety standards and THz therapeutic applications.
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Affiliation(s)
- Olga P. Cherkasova
- Institute of Laser Physics of the Siberian Branch of the Russian Academy of Sciences, Russian Federation
- Novosibirsk State Technical University, Russian Federation
| | - Danil S. Serdyukov
- Institute of Laser Physics of the Siberian Branch of the Russian Academy of Sciences, Russian Federation
- Federal Research Center Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Russian Federation
| | - Eugenia F. Nemova
- Institute of Laser Physics of the Siberian Branch of the Russian Academy of Sciences, Russian Federation
| | - Alexander S. Ratushnyak
- Institute of Computational Technologies of the Siberian Branch of the Russian Academy of Sciences, Russian Federation
| | - Anna S. Kucheryavenko
- Institute of Solid State Physics of the Russian Academy of Sciences, Russian Federation
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Russian Federation
| | - Irina N. Dolganova
- Institute of Solid State Physics of the Russian Academy of Sciences, Russian Federation
- Sechenov University, Institute for Regenerative Medicine, Russian Federation
- Sechenov University, World-Class Research Center “Digital Biodesign and Personalized Healthcare,” Russian Federation
| | - Guofu Xu
- Polytechnique Montreal, Department of Engineering Physics, Canada
| | | | - Igor V. Reshetov
- Sechenov University, Institute for Cluster Oncology, Russian Federation
- Academy of Postgraduate Education FSCC FMBA, Russian Federation
| | - Peter S. Timashev
- Sechenov University, Institute for Regenerative Medicine, Russian Federation
- Sechenov University, World-Class Research Center “Digital Biodesign and Personalized Healthcare,” Russian Federation
- N.N. Semenov Institute of Chemical Physics, Department of Polymers and Composites, Russian Federation
- Lomonosov Moscow State University, Department of Chemistry, Russian Federation
| | - Igor E. Spektor
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Russian Federation
| | - Kirill I. Zaytsev
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Russian Federation
- Sechenov University, Institute for Regenerative Medicine, Russian Federation
- Bauman Moscow State Technical University, Russian Federation
| | - Valery V. Tuchin
- Saratov State University, Russian Federation
- Institute of Precision Mechanics and Control of the Russian Academy of Sciences, Russian Federation
- National Research Tomsk State University, Russian Federation
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9
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Yang J, Wang C. Efficient terahertz generation scheme in a thin-film lithium niobate-silicon hybrid platform. OPTICS EXPRESS 2021; 29:16477-16486. [PMID: 34154210 DOI: 10.1364/oe.419965] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 04/05/2021] [Indexed: 06/13/2023]
Abstract
The terahertz (THz) spectral window is of unique interest for plenty of applications, yet we are still searching for a low-cost, continuous-wave, room-temperature THz source with high generation efficiency. Here, we propose and investigate a hybrid lithium niobate/silicon waveguide scheme to realize such an efficient THz source via difference-frequency generation. The multi-layer structure allows low-loss and strong waveguide confinements at both optical and THz frequencies, as well as a reasonable nonlinear interaction strength between the three associated waves. Our numerical simulation results show continuous-wave THz generation efficiencies as high as 3.5×10-4 W-1 at 3 THz with high tolerance to device fabrication variations, three orders of magnitude higher than current lithium-niobate-based devices. Further integrating the proposed scheme with an optical racetrack resonator could improve the conversion efficiency to 2.1×10-2 W-1. Our proposed THz source could become a compact and cost-effective solution for future spectroscopy, communications and remote sensing systems.
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10
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Lam M, Pal SB, Vogt T, Kiffner M, Li W. Directional THz generation in hot Rb vapor excited to a Rydberg state. OPTICS LETTERS 2021; 46:1017-1020. [PMID: 33649643 DOI: 10.1364/ol.418618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 02/01/2021] [Indexed: 06/12/2023]
Abstract
We optically excite 85Rb atoms in a heated vapor cell to a low-lying Rydberg state 10D5/2 and observe directional terahertz (THz) beams at 3.3 THz and 7.8 THz. These THz fields are generated by amplified spontaneous emission from the 10D5/2 state to the 11P3/2 and 8F7/2 states, respectively. In addition, we observe ultraviolet (UV) light produced by four-wave mixing of optical pump lasers and the 3.3 THz field. We characterize the generated THz power over the detuning and power of pump lasers, and identify experimental conditions favoring THz and UV generation, respectively. Our scheme paves a new pathway towards generating high-power narrowband THz radiation.
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11
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Totero Gongora JS, Peters L, Tunesi J, Cecconi V, Clerici M, Pasquazi A, Peccianti M. All-Optical Two-Color Terahertz Emission from Quasi-2D Nonlinear Surfaces. PHYSICAL REVIEW LETTERS 2020; 125:263901. [PMID: 33449780 DOI: 10.1103/physrevlett.125.263901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/22/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Two-color terahertz (THz) generation is a field-matter process combining an optical pulse and its second harmonic. Its application in condensed matter is challenged by the lack of phase matching among multiple interacting fields. Here, we demonstrate phase-matching-free two-color THz conversion in condensed matter by introducing a highly resonant absorptive system. The generation is driven by a third-order nonlinear interaction localized at the surface of a narrow-band-gap semiconductor, and depends directly on the relative phase between the two colors. We show how to isolate the third-order effect among other competitive THz-emitting surface mechanisms, exposing the general features of the two-color process.
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Affiliation(s)
- J S Totero Gongora
- Emergent Photonics Lab (EPic), Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - L Peters
- Emergent Photonics Lab (EPic), Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - J Tunesi
- Emergent Photonics Lab (EPic), Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - V Cecconi
- Emergent Photonics Lab (EPic), Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - M Clerici
- Ultrafast Nonlinear Optics Lab (UNO), James Watt School of Engineering, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - A Pasquazi
- Emergent Photonics Lab (EPic), Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - M Peccianti
- Emergent Photonics Lab (EPic), Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
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12
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Wienold M, Zubairova A, Hübers HW. Laser emission at 4.5 THz from 15NH 3 and a mid-infrared quantum-cascade laser as a pump source. OPTICS EXPRESS 2020; 28:23114-23121. [PMID: 32752312 DOI: 10.1364/oe.395832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 06/30/2020] [Indexed: 05/28/2023]
Abstract
We present an optically pumped terahertz gas laser, which is based on a mid-infrared quantum-cascade laser as a pump source, a transversely pumped standing wave resonator, and 15NH3 as a gain medium. We observe several laser lines around 4.5 THz, corresponding to rotational transitions in the ν2 band of ammonia. So far, these are the highest frequencies obtained from a QCL-pumped THz gas laser. The involved molecular transitions are unambiguously identified by high-resolution spectroscopy.
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13
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Giant Enhancement of THz Wave Emission under Double-Pulse Excitation of Thin Water Flow. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10062031] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Simultaneous measurements of THz wave and hard X-ray emission from thin and flat water flow when irradiated by double femtosecond laser pulses (800 nm, 35 fs/transform-limited, 0.5 kHz, delay times up to 15 ns) were carried out. THz wave measurements by time-domain spectroscopy and X-ray detection by Geiger counters were performed at the transmission and the reflection sides of the flow. THz wave emission spectra show their dynamic peak shifts toward the low frequency with the highest intensity enhancements more than 1.5 × 10 3 times in |E| 2 accumulated over the whole spectrum range of 0–3 THz at the delay time of 4.7 ns between the two pulses. On the other hand, X-ray intensity enhancements are limited to about 20 times at 0 ns under the same experimental conditions. The mechanisms for the spectral changes and the intensity enhancements in THz wave emission are discussed from the viewpoint of laser ablation on the water flow induced by the pre-pulse irradiation.
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14
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Lampin JF, Pagies A, Santarelli G, Hesler J, Hansel W, Holzwarth R, Barbieri S. Quantum cascade laser-pumped terahertz molecular lasers: frequency noise and phase-locking using a 1560 nm frequency comb. OPTICS EXPRESS 2020; 28:2091-2106. [PMID: 32121907 DOI: 10.1364/oe.379960] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/11/2019] [Indexed: 06/10/2023]
Abstract
We report the measurement of the frequency noise power spectral density (PSD) of a Terahertz (THz) molecular laser (ML) pumped by a mid-infrared (MIR) quantum cascade laser (QCL), and emitting 1 mW at 1.1THz in continuous wave. This is achieved by beating the ML frequency with the 1080th harmonic of the repetition rate of a 1560 nm frequency comb (FC). We find a frequency noise PSD < 10Hz2/Hz (-95dBc/Hz) at 100kHz from the carrier. To demonstrate the effect of the stability of the pump laser on the spectral purity of the THz emission we also measure the frequency noise PSD of a CO2-laser-pumped 2.5THz ML, reaching 0.1Hz2/Hz (-105dBc/Hz) at 40kHz from the carrier, limited by the frequency noise of the FC harmonic. Finally, we show that it is possible to actively phase-lock the QCL-pumped molecular laser to the FC repetition rate harmonic by controlling the QCL current, demonstrating a sub-Hz linewidth.
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