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Dunn A, Poyser C, Dean P, Demić A, Valavanis A, Indjin D, Salih M, Kundu I, Li L, Akimov A, Davies AG, Linfield E, Cunningham J, Kent A. High-speed modulation of a terahertz quantum cascade laser by coherent acoustic phonon pulses. Nat Commun 2020; 11:835. [PMID: 32047146 PMCID: PMC7012870 DOI: 10.1038/s41467-020-14662-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 01/23/2020] [Indexed: 11/28/2022] Open
Abstract
The fast modulation of lasers is a fundamental requirement for applications in optical communications, high-resolution spectroscopy and metrology. In the terahertz-frequency range, the quantum-cascade laser (QCL) is a high-power source with the potential for high-frequency modulation. However, conventional electronic modulation is limited fundamentally by parasitic device impedance, and so alternative physical processes must be exploited to modulate the QCL gain on ultrafast timescales. Here, we demonstrate an alternative mechanism to modulate the emission from a QCL device, whereby optically-generated acoustic phonon pulses are used to perturb the QCL bandstructure, enabling fast amplitude modulation that can be controlled using the QCL drive current or strain pulse amplitude, to a maximum modulation depth of 6% in our experiment. We show that this modulation can be explained using perturbation theory analysis. While the modulation rise-time was limited to ~800 ps by our measurement system, theoretical considerations suggest considerably faster modulation could be possible. The typical electronic modulation of terahertz quantum cascade lasers is fundamentally limited at fast timescales by device properties. Here the authors propose and study an alternative, acoustic mechanism for modulating such THz QCLs at high speed.
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Affiliation(s)
- Aniela Dunn
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| | - Caroline Poyser
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Aleksandar Demić
- 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
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Mohammed Salih
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Iman Kundu
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Lianhe Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Andrey Akimov
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Alexander Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Edmund Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - John Cunningham
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Anthony Kent
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
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Keeley J, Freeman J, Bertling K, Lim YL, Mohandas RA, Taimre T, Li LH, Indjin D, Rakić AD, Linfield EH, Davies AG, Dean P. Measurement of the emission spectrum of a semiconductor laser using laser-feedback interferometry. Sci Rep 2017; 7:7236. [PMID: 28775327 PMCID: PMC5543105 DOI: 10.1038/s41598-017-07432-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 06/28/2017] [Indexed: 11/09/2022] Open
Abstract
The effects of optical feedback (OF) in lasers have been observed since the early days of laser development. While OF can result in undesirable and unpredictable operation in laser systems, it can also cause measurable perturbations to the operating parameters, which can be harnessed for metrological purposes. In this work we exploit this 'self-mixing' effect to infer the emission spectrum of a semiconductor laser using a laser-feedback interferometer, in which the terminal voltage of the laser is used to coherently sample the reinjected field. We demonstrate this approach using a terahertz frequency quantum cascade laser operating in both single- and multiple-longitudinal mode regimes, and are able to resolve spectral features not reliably resolved using traditional Fourier transform spectroscopy. We also investigate quantitatively the frequency perturbation of individual laser modes under OF, and find excellent agreement with predictions of the excess phase equation central to the theory of lasers under OF.
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Affiliation(s)
- James Keeley
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Joshua Freeman
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Karl Bertling
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Yah Leng Lim
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Reshma A Mohandas
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Thomas Taimre
- School of Mathematics and Physics, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Lianhe H Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Dragan Indjin
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Aleksandar D Rakić
- School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Edmund H Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - A Giles Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Paul Dean
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
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Miao W, Lou Z, Xu GY, Hu J, Li SL, Zhang W, Zhou KM, Yao QJ, Zhang K, Duan WY, Shi SC, Colombelli R, Beere HE, Ritchie DA. Demonstration of a fully integrated superconducting receiver with a 2.7 THz quantum cascade laser. OPTICS EXPRESS 2015; 23:4453-8. [PMID: 25836482 DOI: 10.1364/oe.23.004453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We demonstrate for the first time the integration of a superconducting hot electron bolometer (HEB) mixer and a quantum cascade laser (QCL) on the same 4-K stage of a single cryostat, which is of particular interest for terahertz (THz) HEB/QCL integrated heterodyne receivers for practical applications. Two key issues are addressed. Firstly, a low power consumption QCL is adopted for preventing its heat dissipation from destroying the HEB's superconductivity. Secondly, a simple spherical lens located on the same 4-K stage is introduced to optimize the coupling between the HEB and the QCL, which has relatively limited output power owing to low input direct current (DC) power. Note that simulation techniques are used to design the HEB/QCL integrated heterodyne receiver to avoid the need for mechanical tuning. The integrated HEB/QCL receiver shows an uncorrected noise temperature of 1500 K at 2.7 THz, which is better than the performance of the same receiver with all the components not integrated.
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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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Yu N, Wang QJ, Kats MA, Fan JA, Khanna SP, Li L, Davies AG, Linfield EH, Capasso F. Designer spoof surface plasmon structures collimate terahertz laser beams. NATURE MATERIALS 2010; 9:730-735. [PMID: 20693995 DOI: 10.1038/nmat2822] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 06/30/2010] [Indexed: 05/29/2023]
Abstract
Surface plasmons have found a broad range of applications in photonic devices at visible and near-infrared wavelengths. In contrast, longer-wavelength surface electromagnetic waves, known as Sommerfeld or Zenneck waves, are characterized by poor confinement to surfaces and are therefore difficult to control using conventional metallo-dielectric plasmonic structures. However, patterning the surface with subwavelength periodic features can markedly reduce the asymptotic surface plasmon frequency, leading to 'spoof' surface plasmons with subwavelength confinement at infrared wavelengths and beyond, which mimic surface plasmons at much shorter wavelengths. We demonstrate that by directly sculpting designer spoof surface plasmon structures that tailor the dispersion of terahertz surface plasmon polaritons on the highly doped semiconductor facets of terahertz quantum cascade lasers, the performance of the lasers can be markedly enhanced. Using a simple one-dimensional grating design, the beam divergence of the lasers was reduced from approximately 180 degrees to approximately 10 degrees, the directivity was improved by over 10 decibels and the power collection efficiency was increased by a factor of about six compared with the original unpatterned devices. We achieve these improvements without compromising high-temperature performance of the lasers.
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Fathololoumi S, Dupont E, Razavipour SG, Laframboise SR, Delage A, Wasilewski ZR, Bezinger A, Rafi GZ, Safavi-Naeini S, Ban D, Liu HC. Electrically switching transverse modes in high power THz quantum cascade lasers. OPTICS EXPRESS 2010; 18:10036-10048. [PMID: 20588857 DOI: 10.1364/oe.18.010036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The design and fabrication of a high power THz quantum cascade laser (QCL), with electrically controllable transverse mode is presented. The switching of the beam pattern results in dynamic beam switching using a symmetric side current injection scheme. The angular-resolved L-I curves measurements, near-field and far-field patterns and angular-resolved lasing spectra are presented. The measurement results confirm that the quasi-TM(01) transverse mode lases first and dominates the lasing operation at lower current injection, while the quasi-TM(00) mode lases at a higher threshold current density and becomes dominant at high current injection. The near-field and far-field measurements confirm that the lasing THz beam is maneuvered by 25 degrees in emission angle, when the current density changes from 1.9 kA/cm(2) to 2.3 kA/cm(2). A two-dimension (2D) current and mode calculation provides a simple model to explain the behavior of each mode under different bias conditions.
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Affiliation(s)
- S Fathololoumi
- Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, ON, Canada.
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