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Voigt R, Wienold M, Jayasankar D, Drakinskiy V, Stake J, Sobis P, Schrottke L, Lü X, Grahn HT, Hübers HW. Frequency stabilization of a terahertz quantum-cascade laser to the Lamb dip of a molecular absorption line. OPTICS EXPRESS 2023; 31:13888-13894. [PMID: 37157264 DOI: 10.1364/oe.483883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We demonstrate the frequency stabilization of a terahertz quantum-cascade laser (QCL) to the Lamb dip of the absorption line of a D2O rotational transition at 3.3809309 THz. To assess the quality of the frequency stabilization, a Schottky diode harmonic mixer is used to generate a downconverted QCL signal by mixing the laser emission with a multiplied microwave reference signal. This downconverted signal is directly measured by a spectrum analyzer showing a full width at half maximum of 350 kHz, which is eventually limited by high-frequency noise beyond the bandwidth of the stabilization loop.
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2
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Alam T, Wienold M, Lü X, Biermann K, Schrottke L, Grahn HT, Hübers HW. Frequency and power stabilization of a terahertz quantum-cascade laser using near-infrared optical excitation. OPTICS EXPRESS 2019; 27:36846-36854. [PMID: 31873456 DOI: 10.1364/oe.27.036846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 11/07/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate a technique to simultaneously stabilize the frequency and output power of a terahertz quantum-cascade laser (QCL). This technique exploits frequency and power variations upon near-infrared illumination of the QCL with a diode laser. It does not require an external terahertz optical modulator. By locking the frequency to a molecular absorption line, we obtain a long-term (one-hour) linewidth of 260 kHz (full width at half maximum) and a root-mean-square power stability below 0.03%. With respect to the free-running case, this stabilization scheme improves the frequency stability by nearly two orders of magnitude and the power stability by a factor of three.
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3
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Han YJ, Partington J, Chhantyal-Pun R, Henry M, Auriacombe O, Rawlings T, Li LH, Keeley J, Oldfield M, Brewster N, Dong R, Dean P, Davies AG, Ellison BN, Linfield EH, Valavanis A. Gas spectroscopy through multimode self-mixing in a double-metal terahertz quantum cascade laser. OPTICS LETTERS 2018; 43:5933-5936. [PMID: 30547973 DOI: 10.1364/ol.43.005933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 10/10/2018] [Indexed: 06/09/2023]
Abstract
A multimode self-mixing terahertz-frequency gas absorption spectroscopy is demonstrated based on a quantum cascade laser. A double-metal device configuration is used to expand the laser's frequency tuning range, and a precision-micromachined external waveguide module is used to enhance the optical feedback. Methanol spectra are measured using two laser modes at 3.362 and 3.428 THz, simultaneously, with more than eight absorption peaks resolved over a 17 GHz bandwidth, which provide the noise-equivalent absorption sensitivity of 1.20×10-3 cm-1 Hz-1/2 and 2.08×10-3 cm-1 Hz-1/2, respectively. In contrast to all previous self-mixing spectroscopy, our multimode technique expands the sensing bandwidth and duty cycle significantly.
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4
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Chhantyal-Pun R, Valavanis A, Keeley JT, Rubino P, Kundu I, Han Y, Dean P, Li L, Davies AG, Linfield EH. Gas spectroscopy with integrated frequency monitoring through self-mixing in a terahertz quantum-cascade laser. OPTICS LETTERS 2018; 43:2225-2228. [PMID: 29762559 DOI: 10.1364/ol.43.002225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 03/12/2018] [Indexed: 06/08/2023]
Abstract
We demonstrate a gas spectroscopy technique, using self-mixing in a 3.4 terahertz quantum-cascade laser (QCL). All previous QCL spectroscopy techniques have required additional terahertz instrumentation (detectors, mixers, or spectrometers) for system pre-calibration or spectral analysis. By contrast, our system self-calibrates the laser frequency (i.e., with no external instrumentation) to a precision of 630 MHz (0.02%) by analyzing QCL voltage perturbations in response to optical feedback within a 0-800 mm round-trip delay line. We demonstrate methanol spectroscopy by introducing a gas cell into the feedback path and show that a limiting absorption coefficient of ∼1×10-4 cm-1 is resolvable.
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5
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Folland TG, Marshall OP, Beere HE, Ritchie DA, Chakraborty S. Coherent detection of THz laser signals in optical fiber systems. OPTICS EXPRESS 2017; 25:25566-25573. [PMID: 29041222 DOI: 10.1364/oe.25.025566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 08/17/2017] [Indexed: 06/07/2023]
Abstract
Terahertz (THz) coherent detectors are crucial for the stabilization and measurement of the properties of quantum cascade lasers (QCLs). This paper describes the exploitation of intra-cavity sum frequency generation to up-convert the emission of a THz QCL to the near infrared for detection with fiber optic coupled components alone. Specifically, a low cost infrared photodiode is used to detect a radio frequency (RF) signal with a signal-to-noise ratio of approximately 20dB, generated by beating the up-converted THz wave and a near infrared local oscillator. This RF beat note allows direct analysis of the THz QCL emission in time and frequency domains. The application of this technique for QCL characterization is demonstrated by analyzing the continuous tuning of the RF signal over 2 GHz, which arises from mode tuning across the QCL's operational current range.
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6
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Consolino L, Jung S, Campa A, De Regis M, Pal S, Kim JH, Fujita K, Ito A, Hitaka M, Bartalini S, De Natale P, Belkin MA, Vitiello MS. Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation. SCIENCE ADVANCES 2017; 3:e1603317. [PMID: 28879235 PMCID: PMC5580883 DOI: 10.1126/sciadv.1603317] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 08/05/2017] [Indexed: 05/20/2023]
Abstract
Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 × 10-10. The unveiled emission LW (400 kHz at 1-ms integration time) indicates that DFG-QCLs are well suited to operate as local oscillators and to be used for a variety of metrological, spectroscopic, communication, and imaging applications that require narrow-LW THz sources.
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Affiliation(s)
- Luigi Consolino
- Consiglio Nazionale delle Ricerche (CNR)–Istituto Nazionale di Ottica and European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy
| | - Seungyong Jung
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Annamaria Campa
- Consiglio Nazionale delle Ricerche (CNR)–Istituto Nazionale di Ottica and European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy
| | - Michele De Regis
- Consiglio Nazionale delle Ricerche (CNR)–Istituto Nazionale di Ottica and European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy
| | - Shovon Pal
- National Enterprise for nanoScience and nanoTechnology (NEST), CNR–Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Jae Hyun Kim
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Kazuue Fujita
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu 434-8601, Japan
| | - Akio Ito
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu 434-8601, Japan
| | - Masahiro Hitaka
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu 434-8601, Japan
| | - Saverio Bartalini
- Consiglio Nazionale delle Ricerche (CNR)–Istituto Nazionale di Ottica and European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy
| | - Paolo De Natale
- Consiglio Nazionale delle Ricerche (CNR)–Istituto Nazionale di Ottica and European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy
| | - Mikhail A. Belkin
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA
- Corresponding author. (M.A.B.); (M.S.V.)
| | - Miriam Serena Vitiello
- National Enterprise for nanoScience and nanoTechnology (NEST), CNR–Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
- Corresponding author. (M.A.B.); (M.S.V.)
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7
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Keeley J, Dean P, Valavanis A, Bertling K, Lim YL, Alhathlool R, Taimre T, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG. Three-dimensional terahertz imaging using swept-frequency feedback interferometry with a quantum cascade laser. OPTICS LETTERS 2015; 40:994-997. [PMID: 25768165 DOI: 10.1364/ol.40.000994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate coherent three-dimensional terahertz imaging by frequency modulation of a quantum cascade laser in a compact and experimentally simple self-mixing scheme. Through this approach, we can realize significantly faster acquisition rates compared to previous schemes employing longitudinal mechanical scanning of a sample. We achieve a depth resolution of better than 0.1 μm with a power noise spectral density below -50 dB/Hz, for a sampling time of 10 ms/pixel.
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8
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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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9
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Wang T, Liu JQ, Liu FQ, Wang LJ, Zhang JC, Wang ZG. Tri-channel single-mode terahertz quantum cascade laser. OPTICS LETTERS 2014; 39:6612-6615. [PMID: 25490634 DOI: 10.1364/ol.39.006612] [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 report on a compact THz quantum cascade laser source emitting at, individually controllable, three different wavelengths (92.6, 93.9, and 95.1 μm). This multiwavelength laser array can be used as a prototype of the emission source of THz wavelength division multiplex (WDM) wireless communication system. The source consists of three tapered single-mode distributed feedback (DFB) terahertz quantum cascade lasers fabricated monolithically on a single chip. All array elements feature longitudinal as well as lateral single-mode in the entire injection range. The peak output powers of individual lasers are 42, 73, and 37 mW at 10 K, respectively.
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10
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Moon K, Kim N, Shin JH, Yoon YJ, Han SP, Park KH. Continuous-wave terahertz system based on a dual-mode laser for real-time non-contact measurement of thickness and conductivity. OPTICS EXPRESS 2014; 22:2259-2266. [PMID: 24663518 DOI: 10.1364/oe.22.002259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Terahertz (THz) waves have been exploited for the non-contact measurements of thickness and refractive index, which has enormous industrial applicability. In this work, we demonstrate a 1.3-μm dual-mode laser (DML)-based continuous-wave THz system for the real-time measurement of a commercial indium-tin-oxide (ITO)-coated glass. The system is compact, cost-effective, and capable of performing broadband measurement within a second at the setting resolution of 1 GHz. The thickness of the glass and the sheet conductivity of the ITO film were successfully measured, and the measurements agree well with those of broadband pulse-based time domain spectroscopy and Hall measurement results.
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11
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Preußler S, Wenzel N, Braun RP, Owschimikow N, Vogel C, Deninger A, Zadok A, Woggon U, Schneider T. Generation of ultra-narrow, stable and tunable millimeter- and terahertz- waves with very low phase noise. OPTICS EXPRESS 2013; 21:23950-23962. [PMID: 24104306 DOI: 10.1364/oe.21.023950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The interference between two spectral lines of the frequency comb of a fiber femtosecond laser is used to generate millimeter-wave and terahertz tones. The two lines are selected by stimulated Brillouin scattering (SBS) amplification. All other modes are strongly rejected based on polarization discrimination, using the polarization-pulling effect that is associated with SBS. The inherent high spectral quality of a femtosecond fiber laser comb allows generation of millimeter- and terahertz waves with linewidths below 1 Hz, and a phase noise of -105 dBc/Hz at 10 kHz offset. The generation, free-space transmission and detection of continuous waves at 1 THz are demonstrated as well. Lastly, the generated millimeter-wave carriers are modulated by 40 Gbit/s data. The entire system consists of a fiber laser and standard equipment of optical telecommunications. Besides metrology, spectroscopy and astronomy, the method can be utilized for the emergent field of wireless millimeter-wave and THz-communications at ultra-high data rates.
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12
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Maysonnave J, Maussang K, Freeman JR, Jukam N, Madéo J, Cavalié P, Rungsawang R, Khanna SP, Linfield EH, Davies AG, Beere HE, Ritchie DA, Dhillon SS, Tignon J. Mode-locking of a terahertz laser by direct phase synchronization. OPTICS EXPRESS 2012; 20:20855-20862. [PMID: 23037209 DOI: 10.1364/oe.20.020855] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A novel scheme to achieve mode-locking of a multimode laser is demonstrated. Traditional methods to produce ultrashort laser pulses are based on modulating the cavity gain or losses at the cavity roundtrip frequency, favoring the pulsed emission. Here, we rather directly act on the phases of the modes, resulting in constructive interference for the appropriated phase relationship. This was performed on a terahertz quantum cascade laser by multimode injection seeding with an external terahertz pulse, resulting in phase mode-locked terahertz laser pulses of 9 ps duration, characterized unambiguously in the time domain.
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Affiliation(s)
- J Maysonnave
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université P. et M. Curie, Université D. Diderot, 75231 Paris Cedex 05, France
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13
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Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers. Nat Commun 2012; 3:1040. [DOI: 10.1038/ncomms2048] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 08/02/2012] [Indexed: 11/08/2022] Open
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14
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Wienold M, Tahraoui A, Schrottke L, Sharma R, Lü X, Biermann K, Hey R, Grahn HT. Lateral distributed-feedback gratings for single-mode, high-power terahertz quantum-cascade lasers. OPTICS EXPRESS 2012; 20:11207-11217. [PMID: 22565743 DOI: 10.1364/oe.20.011207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report on terahertz quantum-cascade lasers (THz QCLs) based on first-order lateral distributed-feedback (lDFB) gratings, which exhibit continuous-wave operation, high output powers (>8 mW), and single-mode emission at 3.3-3.4 THz. A general method is presented to determine the coupling coefficients of lateral gratings in terms of the coupled-mode theory, which demonstrates that large coupling strengths are obtained in the presence of corrugated metal layers. The experimental spectra are in agreement with simulations of the lDFB cavities, which take into account the reflective end facets.
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Affiliation(s)
- M Wienold
- Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany.
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15
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Wanke MC, Grine AD, Fuller CT, Nordquist CD, Cich MJ, Reno JL, Lee M. Common mode frequency instability in internally phase-locked terahertz quantum cascade lasers. OPTICS EXPRESS 2011; 19:24810-24815. [PMID: 22109509 DOI: 10.1364/oe.19.024810] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Feedback from a diode mixer integrated into a 2.8 THz quantum cascade laser (QCL) was used to phase lock the difference frequencies (DFs) among the Fabry-Perot (F-P) longitudinal modes of a QCL. Approximately 40% of the DF power was phase locked, consistent with feedback loop bandwidth of 10 kHz and phase noise bandwidth ~0.5 MHz. While the locked DF signal has ≤ 1 Hz linewidth and negligible drift over ~30 min, mixing measurements between two QCLs and between a QCL and molecular gas laser show that the common mode frequency stability is no better than a free-running QCL.
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Affiliation(s)
- M C Wanke
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185, USA.
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16
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Ducournau G, Szriftgiser P, Akalin T, Beck A, Bacquet D, Peytavit E, Lampin JF. Highly coherent terahertz wave generation with a dual-frequency Brillouin fiber laser and a 1.55 μm photomixer. OPTICS LETTERS 2011; 36:2044-2046. [PMID: 21633443 DOI: 10.1364/ol.36.002044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Thanks to a portable dual-frequency Brillouin fiber laser and a 1.55 μm photomixer, we report the generation of a highly coherent kilohertz level submillimeter wave emission. Low-cost telecommunications components are used to achieve very simple source architecture. The photomixer is composed of a unitravelling carrier photodiode integrated with an antenna. An emission at 316 GHz is observed and analyzed thanks to heterodyne detection with a signal-to-noise ratio >65 dB and a ~1 kHz linewidth. The phase noise of the proposed source has the same performance at 1.7 and 316 GHz. We show that this source has comparable or better phase noise compared to electrical oscillators and the tunability is much wider.
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Affiliation(s)
- G Ducournau
- Institut d’Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Université Lille 1, Avenue Poincaré, B.P. 60069, F-59652 Villeneuve d’Ascq Cedex, France. ‐lille1.fr
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17
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Jirauschek C. Monte Carlo study of intrinsic linewidths in terahertz quantum cascade lasers. OPTICS EXPRESS 2010; 18:25922-25927. [PMID: 21164938 DOI: 10.1364/oe.18.025922] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Based on a coupled simulation of carrier transport and optical cavity field, the intrinsic linewidth in resonant phonon terahertz quantum cascade lasers is self-consistently analyzed. For high power structures, values on the order of Hz are obtained. Thermal photons are found to play a considerable role at elevated temperatures. A linewidth enhancement factor of 0.5 is calculated for the investigated designs.
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Affiliation(s)
- Christian Jirauschek
- Institute for Nanoelectronics, Technische Universität München, D-80333 Munich, Germany.
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18
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Brenner C, Hofmann M, Scheller M, Shakfa MK, Koch M, Mayorga IC, Klehr A, Erbert G, Tränkle G. Compact diode-laser-based system for continuous-wave and quasi-time-domain terahertz spectroscopy. OPTICS LETTERS 2010; 35:3859-3861. [PMID: 21124545 DOI: 10.1364/ol.35.003859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a multimodal diode-laser-based terahertz (THz) spectroscopy system. In contrast to other laser-based THz setups that provide either cw or broadband THz generation, our configuration combines the advantages of both approaches. Our low complexity setup enables fast switching from cw difference frequency generation to broadband THz emission, enabling sophisticated data analysis like much more complex time domain spectroscopy systems.
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Affiliation(s)
- Carsten Brenner
- Lehrstuhl für Photonik und Terahertztechnologie, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany.
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19
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Gellie P, Barbieri S, Lampin JF, Filloux P, Manquest C, Sirtori C, Sagnes I, Khanna SP, Linfield EH, Davies AG, Beere H, Ritchie D. Injection-locking of terahertz quantum cascade lasers up to 35GHz using RF amplitude modulation. OPTICS EXPRESS 2010; 18:20799-816. [PMID: 20940975 DOI: 10.1364/oe.18.020799] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We demonstrate that the cavity resonance frequency - the round-trip frequency - of Terahertz quantum cascade lasers can be injection-locked by direct modulation of the bias current using an RF source. Metal-metal and single-plasmon waveguide devices with roundtrip frequencies up to 35GHz have been studied, and show locking ranges above 200MHz. Inside this locking range the laser round-trip frequency is phase-locked, with a phase noise determined by the RF-synthesizer. We find a square-root dependence of the locking range with RF-power in agreement with classical injection-locking theory. These results are discussed in the context of mode-locking operation.
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Affiliation(s)
- Pierre Gellie
- Laboratoire Matériaux et Phénomènes Quantiques, Université Paris 7and CNRS UMR 7162, 10 rue A. Domont et L. Duquet, 75205 Paris, France
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20
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Mukherjee P, Gupta B. Terahertz (THz) Frequency Sources and Antennas - A Brief Review. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/s10762-008-9423-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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Danylov AA, Waldman J, Goyette TM, Gatesman AJ, Giles RH, Linden KJ, Neal WR, Nixon WE, Wanke MC, Reno JL. Transformation of the multimode terahertz quantum cascade laser beam into a Gaussian, using a hollow dielectric waveguide. APPLIED OPTICS 2007; 46:5051-5. [PMID: 17676114 DOI: 10.1364/ao.46.005051] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We demonstrate that a short hollow dielectric tube can act as a dielectric waveguide and transform the multimode, highly diverging terahertz quantum cascade laser beam into the lowest order dielectric waveguide hybrid mode, EH(11), which then couples efficiently to the free-space Gaussian mode, TEM(00). This simple approach should enable terahertz quantum cascade lasers to be employed in applications where a spatially coherent beam is required.
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Affiliation(s)
- Andriy A Danylov
- Submillimeter-Wave Technology Laboratory, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
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23
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Quraishi Q, Griebel M, Kleine-Ostmann T, Bratschitsch R. Generation of phase-locked and tunable continuous-wave radiation in the terahertz regime. OPTICS LETTERS 2005; 30:3231-3. [PMID: 16342730 DOI: 10.1364/ol.30.003231] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Broadly tunable phase-stable single-frequency terahertz radiation is generated with an optical heterodyne photomixer. The photomixer is excited by two near-infrared CW diode lasers that are phase locked to the stabilized optical frequency comb of a femtosecond titanium:sapphire laser. The terahertz radiation emitted by the photomixer is downconverted into RF frequencies with a waveguide harmonic mixer and measurement-limited linewidths at the Hertz level are demonstrated.
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Affiliation(s)
- Qudsia Quraishi
- JILA, Department of Physics, University of Colorado and the National Institute of Standards and Technology, Boulder 80309-0440, USA.
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24
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Betz AL, Boreiko RT, Williams BS, Kumar S, Hu Q, Reno JL. Frequency and phase-lock control of a 3 THz quantum cascade laser. OPTICS LETTERS 2005; 30:1837-9. [PMID: 16092362 DOI: 10.1364/ol.30.001837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We have locked the frequency of a 3 THz quantum cascade laser (QCL) to that of a far-infrared gas laser with a tunable microwave offset frequency. The locked QCL line shape is essentially Gaussian, with linewidths of 65 and 141 kHz at the -3 and -10 dB levels, respectively. The lock condition can be maintained indefinitely, without requiring temperature or bias current regulation of the QCL other than that provided by the lock error signal. The result demonstrates that a terahertz QCL can be frequency controlled with 1-part-in-10(8) accuracy, which is a factor of 100 better than that needed for a local oscillator in a heterodyne receiver for atmospheric and astronomic spectroscopy.
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Affiliation(s)
- A L Betz
- Center for Astrophysics and Space Astronomy, UCB 593, University of Colorado, Boulder, Boulder, Colorado 80309, USA.
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Duxbury G, Langford N, McCulloch MT, Wright S. Quantum cascade semiconductor infrared and far-infrared lasers: from trace gas sensing to non-linear optics. Chem Soc Rev 2005; 34:921-34. [PMID: 16239994 DOI: 10.1039/b400914m] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Quantum cascade (QC) laser is an entirely new type of semiconductor device in which the laser wavelength depends on the band-gap engineering. It can be made to operate over a much larger range than lead salt lasers, covering significant parts of both the infrared and submillimetre regions, and with higher output power. In this tutorial review we survey some of the applications of these new lasers, which range from trace gas detection for atmospheric or medical purposes to sub-Doppler and time dependent non-linear spectroscopy.
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Affiliation(s)
- Geoffrey Duxbury
- Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow, UK G4 0NG
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Barbieri S, Alton J, Beere HE, Linfield EH, Ritchie DA, Withington S, Scalari G, Ajili L, Faist J. Heterodyne mixing of two far-infrared quantum cascade lasers by use of a point-contact Schottky diode. OPTICS LETTERS 2004; 29:1632-1634. [PMID: 15309842 DOI: 10.1364/ol.29.001632] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We demonstrate heterodyne mixing of two free-running, multimode, 3.3-THz quantum cascade lasers by use of a point-contact Schottky diode. By temperature tuning the emission wavelength of one laser, a difference frequency signal spanning the 2-4-GHz range is obtained, with a signal-to-noise ratio of 30 dB. The frequency of the heterodyne signal is subject to random fluctuations of a few megahertz, principally from instabilities in the temperatures of the devices. From single-shot measurements we derive an instantaneous linewidth for a single Fabry-Perot mode of 20 kHz, corresponding to an integration time of 3.6 ms.
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Affiliation(s)
- S Barbieri
- TeraView, Ltd., Science Park, Cambridge, UK.
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