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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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Khudchenko A, Pavelev D, Vaks V, Baryshev A. Overview of Techniques for THz QCL phase-locking. EPJ WEB OF CONFERENCES 2018. [DOI: 10.1051/epjconf/201819504003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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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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Danylov A, Erickson N, Light A, Waldman J. Phase locking of 2.324 and 2.959 terahertz quantum cascade lasers using a Schottky diode harmonic mixer. OPTICS LETTERS 2015; 40:5090-5092. [PMID: 26512526 DOI: 10.1364/ol.40.005090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The 23rd and 31st harmonics of a microwave signal generated in a novel THz balanced Schottky diode mixer were used as a frequency stable reference source to phase lock solid-nitrogen-cooled 2.324 and 2.959 THz quantum cascade lasers. Hertz-level frequency stability was achieved, which was maintained for several hours.
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Zhao L, Khanal S, Wu C, Kumar S. Proposal for a broadband THz refractive-index sensor based on quantum-cascade laser arrays. OPTICS EXPRESS 2015; 23:4751-4765. [PMID: 25836511 DOI: 10.1364/oe.23.004751] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Many molecules have strong and characteristic rotational and vibrational transitions at terahertz (THz) frequencies, which makes this frequency range unique for applications in spectroscopic sensing of chemical and biological species. Here, we propose a broadband THz sensor based on arrays of single-mode QCLs, which could be utilized for sensing of the refractive-index of solids or liquids in reflection geometry. The proposed scheme does not require expensive THz detectors and consists of no movable parts. A recently developed antenna-feedback geometry is utilized to enhance optical coupling between two single-mode QCLs, which facilitates optical downconversion of the THz frequency signal to microwave regime. Arrays of THz QCLs emitting at discrete frequencies could be utilized to provide more than 2 THz of spectral coverage to realize a broadband, low-cost, and portable THz sensor.
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Danylov AA, Light AR, Waldman J, Erickson NR, Qian X, Goodhue WD. 2.32 THz quantum cascade laser frequency-locked to the harmonic of a microwave synthesizer source. OPTICS EXPRESS 2012; 20:27908-27914. [PMID: 23262736 DOI: 10.1364/oe.20.027908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Frequency stabilization of a THz quantum cascade laser (QCL) to the harmonic of a microwave source has been accomplished using a Schottky diode waveguide mixer designed for harmonic mixing. The 2.32 THz, 1.0 milliwatt CW QCL is coupled into the signal port of the mixer and a 110 GHz signal, derived from a harmonic of a microwave synthesizer, is coupled into the IF port. The difference frequency between the 21st harmonic of 110 GHz and the QCL is used in a discriminator to adjust the QCL bias current to stabilize the frequency. The short-term frequency jitter is reduced from 550 kHz to 4.5 kHz (FWHM) and the long-term frequency drift is eliminated. This performance is compared to that of several other THz QCL frequency stabilization techniques.
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Affiliation(s)
- Andriy A Danylov
- Photonics Center, Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
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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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Pearson JC, Drouin BJ, Maestrini A, Mehdi I, Ward J, Lin RH, Yu S, Gill JJ, Thomas B, Lee C, Chattopadhyay G, Schlecht E, Maiwald FW, Goldsmith PF, Siegel P. Demonstration of a room temperature 2.48-2.75 THz coherent spectroscopy source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2011; 82:093105. [PMID: 21974571 DOI: 10.1063/1.3617420] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report the first demonstration of a continuous wave coherent source covering 2.48-2.75 THz, with greater than 10% instantaneous tuning bandwidth and having 1-14 μW of output power at room temperature. This source is based on a 91.8-101.8 GHz synthesizer followed by a power amplifier and three cascaded frequency triplers. It demonstrates for the first time that purely electronic solid-state sources can generate a useful amount of power in a region of the electromagnetic spectrum where lasers (solid state or gas) were previously the only available coherent sources. The bandwidth, agility, and operability of this THz source have enabled wideband, high resolution spectroscopic measurements of water, methanol, and carbon monoxide with a resolution and signal-to-noise ratio unmatched by any other existing system, providing new insight in the physics of these molecules. Furthermore, the power and optical beam quality are high enough to observe the Lamb-dip effect in water. The source frequency has an absolute accuracy better than 1 part in 10(12) and the spectrometer achieves sub-Doppler frequency resolution better than 1 part in 10(8). The harmonic purity is better than 25 dB. This source can serve as a coherent signal for absorption spectroscopy, a local oscillator for a variety of heterodyne systems and can be used as a method for precision control of more powerful but much less frequency agile quantum mechanical terahertz sources.
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Affiliation(s)
- John C Pearson
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena California 91109, USA.
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Medvedev IR, Neese CF, Plummer GM, De Lucia FC. Impact of atmospheric clutter on Doppler-limited gas sensors in the submillimeter/terahertz. APPLIED OPTICS 2011; 50:3028-3042. [PMID: 21691371 DOI: 10.1364/ao.50.003028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
It is well known that clutter (spectral interference) from atmospheric constituents can be a severe limit for spectroscopic point sensors, especially where high sensitivity and specificity are required. In this paper, we will show for submillimeter/terahertz (SMM/THz) sensors that use cw electronic techniques the clutter limit for the detection of common target gases with absolute specificity (probability of false alarm ≪ 10⁻¹⁰) is in the ppt (1 part in 10¹²) range or lower. This is because the most abundant atmospheric gases are either transparent to SMM/THz radiation (e.g., CO₂) or have spectra that are very sparse relative to the 10⁵ Doppler-limited resolution elements available (e.g., H₂O). Moreover, the low clutter limit demonstrated for cw electronic systems in the SMM/THz is independent of system size and complexity.
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Affiliation(s)
- Ivan R Medvedev
- Department of Physics, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, USA
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Danylov AA, Goyette TM, Waldman J, Coulombe MJ, Gatesman AJ, Giles RH, Qian X, Chandrayan N, Vangala S, Termkoa K, Goodhue WD, Nixon WE. Terahertz inverse synthetic aperture radar (ISAR) imaging with a quantum cascade laser transmitter. OPTICS EXPRESS 2010; 18:16264-16272. [PMID: 20721012 DOI: 10.1364/oe.18.016264] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A coherent transceiver using a THz quantum cascade (TQCL) laser as the transmitter and an optically pumped molecular laser as the local oscillator has been used, with a pair of Schottky diode mixers in the receiver and reference channels, to acquire high-resolution images of fully illuminated targets, including scale models and concealed objects. Phase stability of the received signal, sufficient to allow coherent image processing of the rotating target (in azimuth and elevation), was obtained by frequency-locking the TQCL to the free-running, highly stable optically pumped molecular laser. While the range to the target was limited by the available TQCL power (several hundred microwatts) and reasonably strong indoor atmospheric attenuation at 2.408 THz, the coherence length of the TQCL transmitter will allow coherent imaging over distances up to several hundred meters. Image data obtained with the system is presented.
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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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Hensley JM, Montoya J, Allen MG, Xu J, Mahler L, Tredicucci A, Beere HE, Ritchie DA. Spectral behavior of a terahertz quantum-cascade laser. OPTICS EXPRESS 2009; 17:20476-20483. [PMID: 19997276 DOI: 10.1364/oe.17.020476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper, the spectral behavior of two terahertz (THz) quantum cascade lasers (QCLs) operating both pulsed and cw is characterized using a heterodyne technique. Both lasers emitting around 2.5 THz are combined onto a whisker contact Schottky diode mixer mounted in a corner cube reflector. The resulting difference frequency beatnote is recorded in both the time and frequency domain. From the frequency domain data, we measure the effective laser linewidth and the tuning rates as a function of both temperature and injection current and show that the current tuning behavior cannot be explained by temperature tuning mechanisms alone. From the time domain data, we characterize the intrapulse frequency tuning behavior, which limits the effective linewidth to approximately 5 MHz.
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Affiliation(s)
- J M Hensley
- Physical Sciences Inc, 20 New England Business Center, Andover, Massachusetts 01810-1077, USA.
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Khosropanah P, Baryshev A, Zhang W, Jellema W, Hovenier JN, Gao JR, Klapwijk TM, Paveliev DG, Williams BS, Kumar S, Hu Q, Reno JL, Klein B, Hesler JL. Phase locking of a 2.7 THz quantum cascade laser to a microwave reference. OPTICS LETTERS 2009; 34:2958-2960. [PMID: 19794781 DOI: 10.1364/ol.34.002958] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We demonstrate the phase locking of a 2.7 THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at approximately 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
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Affiliation(s)
- P Khosropanah
- SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands
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Danylov AA, Goyette TM, Waldman J, Coulombe MJ, Gatesman AJ, Giles RH, Goodhue WD, Qian X, Nixon WE. Frequency stabilization of a single mode terahertz quantum cascade laser to the kilohertz level. OPTICS EXPRESS 2009; 17:7525-7532. [PMID: 19399130 DOI: 10.1364/oe.17.007525] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A simple analog locking circuit was shown to stabilize the beat signal between a 2.408 THz quantum cascade laser and a CH(2)DOH THz CO(2) optically pumped molecular laser to 3-4 kHz (FWHM). This is approximately a tenth of the observed long-term (t approximately sec) linewidth of the optically pumped laser showing that the feedback loop corrects for much of the mechanical and acoustic-induced frequency jitter of the gas laser. The achieved stability should be sufficient to enable the use of THz quantum cascade lasers as transmitters in short-range coherent transceivers.
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Affiliation(s)
- Andriy A Danylov
- Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
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Bielsa F, Douillet A, Valenzuela T, Karr JP, Hilico L. Narrow-line phase-locked quantum cascade laser in the 9.2 microm range. OPTICS LETTERS 2007; 32:1641-3. [PMID: 17572732 DOI: 10.1364/ol.32.001641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We report the operation of a 50 mW continuous-wave quantum cascade laser (QCL) in the 9.2 microm range, phase locked to a single-mode CO(2) laser with a tunable frequency offset. The wide free-running emission spectrum of the QCL (3-5 MHz) is strongly narrowed down to the kilohertz range, making it suitable for high-resolution molecular spectroscopy.
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Affiliation(s)
- Franck Bielsa
- Laboratoire Kastler Brossel, Evry, UPMC, CNRS, ENS, Paris, France
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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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