Center for Quantum Devices - Most Downloaded Journal Articles

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6.	High-power, room-temperature and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ = 4.8 µm J.S. Yu, S. Slivken, S.R. Darvish, A. Evans, B. Gokden and M. Razeghi Virtual Journal of Nanoscale Science and Technology 12 (5)-- August 1, 2005 ...[Visit Journal][reprint (PDF)]
6.	High power 1D and 2D photonic crystal distributed feedback quantum cascade lasers B. Gokden, Y. Bai, S. Tsao, N. Bandyopadhyay, S. Slivken and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-27, 2011), Vol. 7945, p. 79450C-- January 23, 2011 ...[Visit Journal] For many practical applications that need bright sources of mid-infrared radiation, single mode operation and good beam quality are also required. Quantum cascade lasers are prominent candidates as compact sources of mid-infrared radiation capable of delivering very high power both CW and under pulsed operation. While 1D photonic crystal distributed feedback structures can be used to get single mode operation from quantum cascade lasers with narrow ridge widths, novel 2D photonic crystal cavity designs can be used to improve spectral and spatial purity of broad area quantum cascade lasers. In this paper, we demonstrate high power, spatially and spectrally pure operation at room temperature from narrow ridge and broad area quantum cascade lasers with buried 1D and 2D photonic crystal structures. Single mode continuous wave emission at λ = 4.8 μm up to 700 mW in epi-up configuration at room temperature was observed from a 11 μm wide 5 mm long distributed feedback quantum cascade laser with buried 1D gratings. High peak powers up to 34 W was obtained from a 3mm long 400 μm wide 2D photonic crystal distributed feedback laser at room temperature under pulsed operation. The far field profile had a single peak normal to the laser facet and the M2 figure of merit was as low as 2.5. Emission spectrum had a dominating single mode at λ = 4.36 μm. [reprint (PDF)]
6.	Monolithic integration of a short‐length GaInAs photoconductor with a GaAs/GaAlAs optical waveguide on a GaAs semi‐insulating substrate F. Mallecot; J. F. Vinchant; M. Razeghi; D. Vandermoere; J. P. Vilcot; D. Decoster Appl. Phys. Lett. 53, 2522–2524 (1988)-- December 19, 1988 ...[Visit Journal] We report the first fabrication of a GaO. 47 Inn. 53 As planar photoconductive detector, associated with a GaAs/GaAIAs rib waveguide grown on a semi-insulating GaAs substrate, which needs a short-length absorbing layer to detect the optical signal. Because of the GaAIAs epilayer, a GalnAs length of about 100 tl1n only is needed to detect 90% of the opticai signal, accordingly to results predicted using a four-layer model with complex refractive indices in each layer. [reprint (PDF)]
4.	Comparison of PLD-Grown p-NiO/n-Ga2O3 Heterojunctions on Bulk Single Crystal β-Ga2O3 and r-plane Sapphire Substrates D. J. Rogers , V. E. Sandana, F. Hosseini Teherani and M. Razeghi Proc. of SPIE Vol. 12895, Quantum Sensing and Nano Electronics and Photonics XX, 128870J (28 January - 1 February 2024 San Francisco)doi: 10.1117/12.3012511 ...[Visit Journal] p-NiO/n-Ga2O3 heterostructures were formed on single crystal (-201) β (monoclinic) Ga2O3 and r-sapphire substrates by Pulsed Laser Deposition. Ring mesa layer stacks were created using a shadow mask during growth. X-Ray diffraction studies were consistent with the formation of (111) oriented fcc NiO on the bulk Ga2O3 and randomly oriented fcc NiO on (102) oriented β-Ga2O3 /r-sapphire. RT optical transmission studies revealed bandgap energy values of ~3.65 eV and ~5.28 eV for the NiO and Ga2O3 on r-sapphire. p-n junction devices were formed by depositing gold contacts on the layer stacks using shadow masks in a thermal evaporator. Both heterojunctions showed rectifying I/V characteristics. On bulk Ga2O, the junction showed a current density over 16mA/cm2 at +20V forward bias and a reverse bias leakage current over 3 orders of magnitude lower at -20V (1 pA). On Ga2O3/r-sapphire the forward bias current density at +15V was about an order of magnitude lower than for the p-NiO/bulk n-Ga2O3 heterojunction while the reverse bias leakage current at -15V (~ 20 pA) was an order of magnitude higher. Hence the NiO/bulk Ga2O3 junction was more rectifying. Upon illumination with a Xenon lamp a distinct increase in current was observed for the IV curves in both devices (four orders of magnitude for -15V reverse bias in the case of the p-NiO/bulk n-Ga2O3 heterojunction). The p-NiO/n-Ga2O3/rsapphire junction gave a spectral responsivity with a FWHM value of 80nm and two distinct response peaks (with maxima at 230 and 270nm) which were attributed to carriers being photogenerated in the Ga2O3 underlayer. For both devices time response studies showed a 10%/90% rise and fall of the photo generated current upon shutter open and closing which was relatively abrupt (millisecond range), and there was no evidence of significant persistent photoconductivity. [reprint (PDF)]
4.	Modeling the electronic band-structure of strained long-wavelength Type-II superlattices using the scattering matrix method Abbas Haddadi，Gail Brown，Manijeh Razeghi Abbas Haddadi,Brown Gail and Razeghi Manijeh.Modeling the electronic band-structure of strained long-wavelength Type-II superlattices using the scattering matrix method[J].Journal of Infrared and Millimeter Waves,2025,44(3):345~350 ...[Visit Journal] This study introduces a comprehensive theoretical framework for accurately calculating the electronic band-structure of strained long-wavelength InAs/GaSb type-II superlattices. Utilizing an eight-band k ⋅ p Hamilto⁃ nian in conjunction with a scattering matrix method， the model effectively incorporates quantum confinement， strain effects， and interface states. This robust and numerically stable approach achieves exceptional agreement with experimental data， offering a reliable tool for analyzing and engineering the band structure of complex multi⁃ layer systems
3.	Geiger-Mode Operation of AlGaN Avalanche Photodiodes at 255 nm Lakshay Gautam, Alexandre Guillaume Jaud, Junhee Lee, Gail J. Brown, Manijeh Razeghi Published in: IEEE Journal of Quantum Electronics ( Volume: 57, Issue: 2, April 2021) ...[Visit Journal] We report the Geiger mode operation of back-illuminated AlGaN avalanche photodiodes. The devices were fabricated on transparent AlN templates specifically for back-illumination to leverage hole-initiated multiplication. The spectral response was analyzed with a peak detection wavelength of 255 nm with an external quantum efficiency of ~14% at zero bias. Low-photon detection capabilities were demonstrated in devices with areas 25 μm×25 μm. Single photon detection efficiencies of ~5% were achieved. [reprint (PDF)]
3.	III-Nitride Optoelectronic Devices: From Ultraviolet Toward Terahertz M. Razeghi IEEE Photonics Journal-Breakthroughs in Photonics 2010, Vol. 3, No. 2, p. 263-267-- April 26, 2011 ...[Visit Journal] We review III-Nitride optoelectronic device technologies with an emphasis on recent breakthroughs. We start with a brief summary of historical accomplishments and then report the state-of-the-art in three key spectral regimes: (1) Ultraviolet (AlGaN-based avalanche photodiodes, single photon detectors, focal plane arrays, and light emitting diodes), (2) Visible (InGaN-based solid state lighting, lasers, and solar cells), and (3) Near-, mid-infrared, and terahertz (AlGaN/GaN-based gap-engineered intersubband devices). We also describe future trends in III-Nitride optoelectronic devices. [reprint (PDF)]
3.	High-performance short-wavelength infrared photodetectors based on type-II InAs/InAs1-xSbx/AlAs1-xSbx superlattices A. Haddadi, X.V. Suo, S. Adhikary, P. Dianat, R. Chevallier, A.M. Hoang, and M. Razeghi Applied Physics Letters 107 , 141104-- October 5, 2015 ...[Visit Journal] A high-performance short-wavelength infrared n-i-p photodiode based on InAs/InAs1-xSbx/AlAs1-xSbx type-II superlattices on GaSb substrate has been demonstrated. The device is designed to have a 50% cut-off wavelength of ~1.8μm at 300K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.47 A/W at 1.6μm, corresponding to a quantum efficiency of 37% at zero bias under front-side illumination, without any anti-reflection coating. With an R×A of 285 Ω·cm² and a dark current density of 9.6×10^-5 A/cm² under −50mV applied bias at 300 K, the photodiode exhibited a specific detectivity of 6.45×10¹⁰ cm·Hz^½/W. At 200 K, the photodiode exhibited a dark current density of 1.3×10^-8 A/cm² and a quantum efficiency of 36%, resulting in a detectivity of 5.66×10¹² cm·Hz^½/W. [reprint (PDF)]
3.	High Performance InAs/InAsSb Type-II Superlattice Mid-Wavelength Infrared Photodetectors with Double Barrier Donghai Wu, Jiakai Li, Arash Dehzangi, Manijeh Razeghi Infrared Physics &Technology 103439-- July 18, 2020 ...[Visit Journal] By introducing a double barrier design, a high performance InAs/InAsSb type-II superlattice mid-wavelength infrared photodetector has been demonstrated. The photodetector exhibits a cut-off wavelength of ~4.50 µm at 150 K. At 150 K and −120 mV applied bias, the photodetector exhibits a dark current density of 1.21 × 10−5 A/cm2, a quantum efficiency of 45% at peak responsivity (~3.95 µm), and a specific detectivity of 6.9 × 1011 cm·Hz1/2/W. The photodetector shows background-limited operating temperature up to 160 K. [reprint (PDF)]
2.	Ga₂O₃ Metal-oxide-semiconductor Field Effect Transistors on Sapphire Substrate by MOCVD Ji-Hyeon Park, Ryan McClintock and Manijeh Razeghi Semiconductor Science and Technology, Volume 34, Number 8-- June 26, 2019 ...[Visit Journal] Si-doped gallium oxide (Ga₂O₃) thin films were grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition (MOCVD) and fabricated into metal oxide semiconductor field effect transistors (MOSFETs). The Ga₂O₃ MOSFETs exhibited effective gate modulation of the drain current with a complete channel pinch-off for VG < −25 V, and the three-terminal off-state breakdown voltage was 390 V. The device shows a very low gate leakage current (~50 pA/mm), which led to a high on/off ratio of ~10⁸. These transistor characteristics were stable from room temperature to 250 °C [reprint (PDF)]
2.	Growth and Characterization of Type-II Non-Equilibrium Photovoltaic Detectors for Long Wavelength Infrared Range H. Mohseni, J. Wojkowski, A. Tahraoui, M. Razeghi, G. Brown and W. Mitche SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] Growth and characterization of type-II detectors for mid-IR wavelength range is presented. The device has a p-i-n structure is designed to operate in the non-equilibrium mode with low tunneling current. The active layer is a short period InAs/GaSb superlattice. Wider bandgap p-type AlSb and n-type InAs layers are used to facilitate the extraction of both electronics and holes from the active layer for the first time. The performance of these devices were compared to the performance of devices grown at the same condition, but without the AlSb barrier layers. The processed devices with the AlSb barrier show a peak responsivity of about 1.2 A/W with Johnson noise limited detectivity of 1.1 X 10¹¹ cm·Hz^½/W at 8 μm at 80 K at zero bias. The details of the modeling, growth, and characterizations will be presented. [reprint (PDF)]
2.	Current status and potential of high power mid-infrared intersubband lasers S. Slivken, Y. Bai, B. Gokden, S.R. Darvish and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7608, p. 76080B-1-- January 22, 2010 ...[Visit Journal] Some of the recent advances in high power quantum cascade laser development will be reviewed in this paper. Research areas explored include short wavelength (λ <4 µm) lasers, high performance strain-balanced heterostructures, and high power long wavelength (7< λ< 16 µm) lasers. Near λ=4.5 µm, highlights include demonstration of 18% continuous wave wallplug efficiency at room temperature, 53% pulsed wallplug efficiency at 40 K, and 120 W of peak power output from a single device at room temperature. Near λ ~10 µm, up to 0.6 W of continuous output power at room temperature has also been demonstrated, with pulsed efficiencies up to 9%. [reprint (PDF)]
2.	Mid‑wavelength infrared avalanche photodetector with AlAsSb/GaSb superlattice Jiakai Li, Arash Dehzangi, Gail Brown, Manijeh Razeghi Scientifc Reports \| (2021) 11:7104 \| https://doi.org/10.1038/s41598-021-86566-8 ...[Visit Journal] In this work, a mid-wavelength infrared separate absorption and multiplication avalanche photodiode (SAM-APD) with 100% cut-of wavelength of ~ 5.0 µm at 200 K grown by molecular beam epitaxy was demonstrated. The InAsSb-based SAM-APD device was designed to have electron dominated avalanche mechanism via the band structure engineered multi-quantum well structure based on AlAsSb/GaSb H-structure superlattice and InAsSb material in the multiplication region. The device exhibits a maximum multiplication gain of 29 at 200 K under -14.7 bias voltage. The maximum multiplication gain value for the MWIR SAM-APD increases from 29 at 200 K to 121 at 150 K. The electron and hole impact ionization coefficients were derived and the large difference between their value was observed. The carrier ionization ratio for the MWIR SAM-APD device was calculated to be ~ 0.097 at 200 K. [reprint (PDF)]
2.	Room Temperature, Continuous Wave Quantum Cascade Laser Grown Directly on a Si Wafer Steven Slivken and Manijeh Razeghi S. Slivken and M. Razeghi,, Journal of Quantum Electronics, Vol. 59, No. 4, doi: 10.1109/JQE.2023.3282710 ...[Visit Journal] We report the room temperature demonstration of a high power, continuous wave, LWIR quantum cascade laser grown directly on a Si substrate. A new wafer, based on a high efficiency, strain-balanced laser core was processed into a lateral injection buried heterostructure laser geometry. A pulsed efficiency of 11.1% was demonstrated at room temperature, with an emission wavelength of 8.35 μm. With low fidelity, epilayer-up packaging, CW emission up to 343 K was also demonstrated, with a maximum output power of >0.7 W near room temperature. [reprint (PDF)]
2.	Broad area photonic crystal distributed feedback quantum cascade lasers emitting 34 W at λ ~ 4.36 μm B. Gokden, Y. Bai, N. Bandyopadhyay, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 97, No. 13, p. 131112-1-- September 27, 2010 ...[Visit Journal] We demonstrate room temperature, high power, single mode, and diffraction limited operation of a two dimensional photonic crystal distributed feedback quantum cascade laser emitting at 4.36 μm. Total peak power up to 34 W is observed from a 3 mm long laser with 400 μm cavity width at room temperature. Far-field profiles have M2 figure of merit as low as 2.5. This device represents a significant step toward realization of spatially and spectrally pure broad area high power quantum cascade lasers. [reprint (PDF)]
2.	High-performance short-wavelength infrared photodetectors based on type-II InAs/InAs_1-xSb_x/AlAs_1-xSb_x superlattices M. Razeghi, A. Haddadi, X. V. Suo, S. Adhikary, P. Dianat, R. Chevallier, A. M. Hoang, A. Dehzangi Proc. SPIE 9819, Infrared Technology and Applications XLII, 98190A -- May 20, 2016 ...[Visit Journal] We present a high-performance short-wavelength infrared n-i-p photodiode, whose structure is based on type-II superlattices with InAs/InAs_1-xSb_x/AlAs_1-xSb_x on GaSb substrate. At room temperature (300K) with front-side illumination, the device shows the peak responsivity of 0.47 A/W at 1.6mm, corresponding to 37% quantum efficiency at zero bias. At 300K, the device has a 50% cut-off wavelength of ~1.8mm. For −50mV applied bias at 300 K the photodetector has dark current density of 9.6x10^-5 A/cm² and RxA of 285 Ω•cm², and it revealed a detectivity of 6.45x10¹⁰ cm•Hz^½/W. Dark current density reached to 1.3x10^-8 A/cm² at 200 K, with 36% quantum efficiency which leads to the detectivity value of 5.66x10¹² cm•Hz^½/W. [reprint (PDF)]
2.	High-quality MOCVD-grown heteroepitaxial gallium oxide growth on III-nitrides enabled by AlOx interlayer Junhee Lee, Lakshay Gautam, and Manijeh Razeghi Junhee Lee, Manijeh RazeghiAppl. Phys. Lett. 123, 151902 (2023) https://doi.org/10.1063/5.0170383 ...[Visit Journal] We report high-quality Ga2O3 grown on an AlGaN/AlN/Sapphire in a single growth run in the same Metal Organic Chemical Vapor Deposition reactor with an AlOx interlayer at the Ga2O3/AlGaN interface. AlOx interlayer was found to enable the growth of single crystalline Ga2O3 on AlGaN in spite of the high lattice mismatch between the two material systems. The resulting nitride/oxide heterogenous heterostructures showed superior material qualities, which were characterized by structural, electrical, and optical characterization techniques. In particular, a significant enhancement of the electron mobility of the nitride/oxide heterogenous heterostructure is reported when compared to the individual electron mobilities of the Ga2O3 epilayer on the sapphire substrate and the AlGaN/AlN heterostructure on the sapphire substrate. This enhanced mobility marks a significant step in realizing the next generation of power electronic devices and transistors. [reprint (PDF)]
2.	Type-II superlattice-based heterojunction phototransistors for high speed applications Jiakai Li, Arash Dehzangi, Donghai Wu, Ryan McClintock, Manijeh Razeghi Infrared Physics and Technology 108, 1033502-- May 2, 2020 ...[Visit Journal] In this study, high speed performance of heterojunction phototransistors (HPTs) based on InAs/GaSb/AlSb type-II superlattice with 30 nm base thickness and 50% cut-off wavelength of 2.0 μm at room temperature are demonstrated. We studied the relationship between -3 dB cut-off frequency of these HPT versus mesa size, applied bias, and collector layer thickness. For 8 μm diameter circular mesas HPT devices with a 0.5 μm collector layer, under 20 V applied bias voltage, we achieved a -3 dB cut-off frequency of 2.8 GHz. [reprint (PDF)]
2.	Extended short wavelength infrared heterojunction phototransistors based on type II superlattices Arash Dehzangi , Ryan McClintock, Donghai Wu , Abbas Haddadi, Romain Chevallier , and Manijeh Razeghi Applied Physics Letters 114, 191109-- May 17, 2019 ...[Visit Journal] A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb on a GaSb substrate is designed, fabricated, and investigated. With the base thickness of 40 nm, the device exhibited a 100% cut-off wavelength of 2.3 λ at 300 K. The saturated peak responsivity value is 320.5 A/W at 300 K, under front-side illumination without any antireflection coating. A saturated optical gain of 245 at 300K was measured. At the same temperature, the device exhibited a collector dark current density (at unity optical gain) and a DC current gain of 7.8 X 10³ A/cm² and 1100, respectively. The device exhibited a saturated dark current shot noise limited specific detectivity of 4.9 X 10¹¹ cm·Hz^½/W at 300 K which remains constant over a broad range of wavelengths and applied biases. [reprint (PDF)]
2.	Performance analysis of infrared heterojunction phototransistors based on Type-II superlattices Jiakai Li, Arash Dehzangi, Manijeh Razeghi Infrared Physics & Technology Volume 113, March 2021, 103641 ...[Visit Journal] In this study, a comprehensive analysis of the n-p-n infrared heterojunction phototransistors (HPTs)based on Type-II superlattices has been demonstrated. Different kinds of Type-II superlattices were carefully chosen for the emitter, base, and collector to improve the optical performance. The effects of different device parameters include emitter doping concentration, base doping concentration, base thickness and energy bandgap difference between emitter and base on the optical gain of the HPTs have been investigated. By scaling the base thickness to 20 nm, the HPT exhibits an optical gain of 345.3 at 1.6 μm at room temperature. For a 10 μm diameter HPT device, a −3 dB cut-off frequency of 5.1 GHz was achieved under 20 V at 150 K. [reprint (PDF)]
2.	Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattices with an AlAsSb/GaSb superlattice barrier A. Haddadi, R. Chevallier, A. Dehzangi, and M. Razeghi Applied Physics Letters 110, 101104-- March 8, 2017 ...[Visit Journal] Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate have been demonstrated. An AlAsSb/GaSb H-structure superlattice design was used as the large-bandgap electron-barrier in these photodetectors. The photodetector is designed to have a 100% cut-off wavelength of ∼2.8 μm at 300 K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.65 A/W at 1.9 μm, corresponding to a quantum efficiency of 41% at zero bias under front-side illumination, without any anti-reflection coating. With an R × A of 78 Ω·cm² and a dark current density of 8 × 10⁻³ A/cm² under −400 mV applied bias at 300 K, the nBn photodetector exhibited a specific detectivity of 1.51 × 10¹⁰ Jones. At 150 K, the photodetector exhibited a dark current density of 9.5 × 10⁻⁹ A/cm² and a quantum efficiency of 50%, resulting in a detectivity of 1.12 × 10¹³ Jones. [reprint (PDF)]
2.	Scaling in back-illuminated GaN avalanche photodiodes K. Minder, J.L. Pau, R. McClintock, P. Kung, C. Bayram, M. Razeghi and D. Silversmith Applied Physics Letters, Vol. 91, No. 7, p. 073513-1-- August 13, 2007 ...[Visit Journal] Avalanche p-i-n photodiodes of various mesa areas were fabricated on AlN templates for back illumination for enhanced performance through hole-initiated multiplication, and the effects of increased area on device performance were studied. Avalanche multiplication was observed in mesa sizes up to 14,063 µm^2 under linear mode operation. Uniform gain and a linear increase of the dark current with area were demonstrated. [reprint (PDF)]
2.	Type-II superlattice dual-band LWIR imager with M-barrier and Fabry-Perot resonance E.K. Huang, A. Haddadi, G. Chen, B.M. Nguyen, M.A. Hoang, R. McClintock, M. Stegall, and M. Razeghi OSA Optics Letters, Vol. 36, No. 13, p. 2560-2562-- July 1, 2011 ...[Visit Journal] We report a high performance long-wavelength IR dual-band imager based on type-II superlattices with 100% cutoff wavelengths at 9.5 μm (blue channel) and 13 μm (red channel). Test pixels reveal background-limited behavior with specific detectivities as high as ∼5×10¹¹ Jones at 7.9 μm in the blue channel and ∼1×10¹¹ Jones at 10.2 μm in the red channel at 77 K. These performances were attributed to low dark currents thanks to the M-barrier and Fabry–Perot enhanced quantum efficiencies despite using thin 2 μm absorbing regions. In the imager, the high signal-to-noise ratio contributed to median noise equivalent temperature differences of ∼20 mK for both channels with integration times on the order of 0.5 ms, making it suitable for high speed applications. [reprint (PDF)]
2.	8-13 μm InAsSb heterojunction photodiode operating at near room temperature J.D. Kim, S. Kim, D. Wu, J. Wojkowski, J. Xu, J. Piotrowski, E. Bigan, and M. Razeghi Applied Physics Letters 67 (18)-- October 30, 1995 ...[Visit Journal] p⁺-InSb/π-InAs_1−xSb_x/n⁺-InSb heterojunction photodiodes operating at near room temperature in the 8–13 μm region of infrared (IR) spectrum are reported. A room‐temperature photovoltaic response of up to 13 μm has been observed at 300 K with an x≊0.85 sample. The voltage responsivity‐area product of 3×10⁻⁵ V· cm²/W has been obtained at 300 K for the λ=10.6 μm optimized device. This was close to the theoretical limit set by the Auger mechanism, with a detectivity at room temperature of ≊1.5×10⁸ cm ·Hz^½/W. [reprint (PDF)]
1.	Room temperature quantum cascade lasers with 22% wall plug efficiency in continuous-wave operation F. Wang, S. Slivken, D. H. Wu, and M. Razeghi Optics Express Vol. 28, Issue 12, pp. 17532-17538-- June 8, 2020 ...[Visit Journal] We report the demonstration of quantum cascade lasers (QCLs) with improved eﬃciency emitting at a wavelength of 4.9 µm in pulsed and continuous-wave(CW)operation. Based on an established design and guided by simulation, the number of QCL-emitting stages is increased in order to realize a 29.3% wall plug eﬃciency (WPE) in pulsed operation at room temperature. With proper fabrication and packaging, a 5-mm-long, 8-µm-wide QCL with a buried ridge waveguide is capable of 22% CW WPE and 5.6 W CW output power at room temperature. This corresponds to an extremely high optical density at the output facet of ∼35 MW/cm², without any damage. [reprint (PDF)]

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