Resonant-Phonon Terahertz Quantum-Cascade Lasers and Video-Rate Terahertz Imaging

We review the development of terahertz quantum-cascade lasers (QCLs) that can be uniquely qualified based on a resonant-phonon depopulation scheme. Record performances in terms of operating temperature and optical power output are reported. The best temperature performance is achieved in the metal-metal (MM) waveguides, which provide near-unity mode confinement and low waveguiding loss at terahertz (THz) frequencies even for cavities with subwavelength dimensions. A pulsed operation up to a heat-sink temperature of 169 K at v ~ 2.7 THz and a continuous-wave (CW) operation up to 117 K at v ~ 3 THz are demonstrated with a five-level design that has a two-well injector region. Some of the key temperature degradation mechanisms for this design are discussed. For operation at lower frequencies (v < 2 THz), a one-well injector design is developed that reduces intersubband absorption losses in the injector region. A QCL operating at v = 1.59 THz (lambda = 188.5 mum) up to a heat-sink temperature of 71 K in cw mode is demonstrated with that design. To obtain high-power output and low beam divergence from the MM waveguides, a lens-coupled scheme is demonstrated. A peak power output of 145 mW, a beam width of 4.8deg, and a maximum lasing temperature of 160 K are obtained from a 4.1 THz QCL in this configuration. In the latter part of the paper, we report on the demonstration of video-rate (20 frames/s) terahertz imaging with QCLs as the source for illumination and a 320 times 240 element room-temperature microbolometer focal plane array as the detector. The QCLs for the imaging system are processed into semiinsulating surface-plasmon waveguides, and are operated in a cryogen-free thermomechanical cooler in quasi-CW mode at a heat-sink temperature of ~30 K. Real-time imaging in transmission mode is demonstrated at a standoff distance of 25 m with a v ~ 4.9 THz QCL in this setup.

[1]  E. Haller.  Advanced far-infrared detectors , 1993 .

[2]  F. Capasso,et al.  Recent progress in quantum cascade lasers and applications , 2001 .

[3]  David A. Ritchie,et al.  Terahertz quantum cascade laser as local oscillator in a heterodyne receiver. , 2005, Optics express.

[4]  G. Bastiaans,et al.  Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz. , 2007, Optics express.

[5]  Giles Davies,et al.  Far-infrared (λ≃87 μm) bound-to-continuum quantum-cascade lasers operating up to 90 K , 2003 .

[6]  Leavitt Rp.  Empirical two-band model for quantum wells and superlattices in an electric field. , 1991 .

[7]  Marcella Giovannini,et al.  Small optical volume terahertz emitting microdisk quantum cascade lasers , 2007 .

[8]  Qing Hu,et al.  Importance of electron-impurity scattering for electron transport in terahertz quantum-cascade lasers , 2004 .

[9]  Qing Hu,et al.  Resonant-phonon terahertz quantum-cascade laser operating at 2.1 THz (λ≃141 µm) , 2004 .

[10]  Qing Hu,et al.  Importance of coherence for electron transport in terahertz quantum cascade lasers , 2005 .

[11]  Qing Hu,et al.  High-power and high-temperature THz quantum-cascade lasers based on lens-coupled metal-metal waveguides. , 2007, Optics letters.

[12]  S. Kumar,et al.  Real-time imaging using a 4.3-THz quantum cascade laser and a 320 /spl times/ 240 microbolometer focal-plane array , 2006, IEEE Photonics Technology Letters.

[13]  S. Kumar,et al.  Long wavelength terahertz quantum-cascade lasers with one-well injector , 2006, 2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference.

[14]  Qing Hu,et al.  Beam patterns of terahertz quantum cascade lasers with subwavelength cavity dimensions , 2006 .

[15]  Qing Hu,et al.  Intrawell and interwell intersubband transitions in multiple quantum wells for far‐infrared sources , 1996 .

[16]  Vincenzo Spagnolo,et al.  Measurement of subband electronic temperatures and population inversion in THz quantum-cascade lasers , 2004 .

[17]  Qing Hu,et al.  3.4-THz quantum cascade laser based on longitudinal-optical-phonon scattering for depopulation , 2003 .

[18]  Qing Hu,et al.  Distributed-feedback terahertz quantum-cascade lasers with laterally corrugated metal waveguides. , 2005, Optics letters.

[19]  P. Taday,et al.  Nondestructive analysis of tablet coating thicknesses using terahertz pulsed imaging. , 2005, Journal of pharmaceutical sciences.

[20]  Qing Hu,et al.  Surface-emitting distributed feedback terahertz quantum-cascade lasers in metal-metal waveguides. , 2007, Optics express.

[21]  Qing Hu,et al.  Electromagnetic modeling of terahertz quantum cascade laser waveguides and resonators , 2005 .

[22]  J. Faist,et al.  Quantum Cascade Laser , 1994, Science.

[23]  Qing Hu,et al.  High-power terahertz quantum cascade lasers , 2006, QELS 2006.

[24]  Mattias Beck,et al.  Imaging with a Terahertz quantum cascade laser. , 2004, Optics express.

[25]  T. M. Klapwijk,et al.  Antenna model for wire lasers. , 2006, Physical review letters.

[26]  B. Williams.  Terahertz quantum cascade lasers , 2007, 2008 Asia Optical Fiber Communication & Optoelectronic Exposition & Conference.

[27]  Edmund Linfield,et al.  Terahertz emission from quantum cascade lasers in the quantum Hall regime: evidence for many body resonances and localization effects. , 2004, Physical review letters.

[28]  P. Collot,et al.  Quantum Cascade Lasers , 1997, CLEO/Europe Conference on Lasers and Electro-Optics.

[29]  P. Siegel.  Terahertz Technology , 2001 .

[30]  L. Esaki,et al.  Resonant tunneling in semiconductor double barriers , 1974 .

[31]  B. Williams,et al.  Quantum-Cascade Lasers with One-Well Injector Operating at 1.59 THz (λ = 188.5 μm) , 2007, 2007 Conference on Lasers and Electro-Optics (CLEO).

[32]  L. Esaki,et al.  Tunneling in a finite superlattice , 1973 .

[33]  D. Rutledge,et al.  INTEGRATED-CIRCUIT ANTENNAS. , 1983 .

[34]  Scott W. Corzine,et al.  High-power quantum cascade lasers grown by low-pressure metal organic vapor-phase epitaxy operating in continuous wave above 400K , 2006 .

[35]  Carlo Sirtori,et al.  Terahertz microcavity lasers with subwavelength mode volumes and thresholds in the milliampere range , 2007 .

[36]  Neal R. Butler,et al.  Low-cost uncooled microbolometer imaging system for dual use , 1995, Optics & Photonics.

[37]  Qing Hu,et al.  Operation of terahertz quantum-cascade lasers at 164 K in pulsed mode and at 117 K in continuous-wave mode. , 2005, Optics express.

[38]  Manijeh Razeghi,et al.  Buried heterostructure quantum cascade lasers with high continuous-wave wall plug efficiency , 2007 .

[39]  Qing Hu,et al.  Terahertz quantum-cascade laser at λ≈100 μm using metal waveguide for mode confinement , 2003 .

[40]  Federico Capasso,et al.  Surface emitting terahertz quantum cascade laser with a double-metal waveguide. , 2006, Optics express.

[41]  Qing Hu,et al.  Real-Time Imaging Using a 4 . 3-THz Quantum Cascade Laser and a 320 240 Microbolometer Focal-Plane Array , 2006 .

[42]  Kodo Kawase,et al.  Terahertz Imaging For Drug Detection And Large-Scale Integrated Circuit Inspection , 2004 .

[43]  Jérôme Faist,et al.  Quantum cascade lasers operating from 1.2to1.6THz , 2007 .

[44]  Carlo Sirtori,et al.  Resonant tunneling in quantum cascade lasers , 1998 .

[45]  Federico Capasso,et al.  Sequential resonant tunneling through a multiquantum well superlattice , 1986 .

[46]  Jérôme Faist,et al.  Horn antennas for terahertz quantum cascade lasers , 2007 .

[47]  Wai Lam Chan,et al.  Imaging with terahertz radiation , 2007 .

[48]  Mattias Beck,et al.  Continuous Wave Operation of a Mid-Infrared Semiconductor Laser at Room Temperature , 2001, Science.

[49]  A. Lee,et al.  Real-time terahertz imaging over a standoff distance (>25meters) , 2006 .

[50]  Qing Hu,et al.  Resonant-phonon-assisted THz quantum-cascade lasers with metal–metal waveguides , 2005 .

[51]  E. Linfield,et al.  Terahertz semiconductor-heterostructure laser , 2002, Nature.

[52]  Federico Capasso,et al.  QUANTUM CASCADE LASERS , 1999 .