29 January 2008 High-temperature and high-power operation of terahertz quantum-cascade lasers
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We summarize recent development of terahertz quantum-cascade lasers (QCLs) based on a resonant-phonon active region design and metal-metal waveguides for mode confinement. Maximum pulsed operating temperature of 169 K is demonstrated for a 2.7 THz design. Lasers processed with the semi-insulating surface-plasmon (SISP) waveguides and the metal-metal (MM) waveguides are experimentally compared. Whereas the SISP waveguides have higher out-coupling efficiencies, the MM waveguides demonstrate improved temperature performance owing to their lower-loss and near unity mode confinement; however, this comes at the cost of poor radiation patterns and low output power. The beam quality and the out-coupling efficiency of the MM waveguides is shown to be significantly improved by abutting a silicon hyperhemispherical lens to the cleaved facets of ridge lasers. Whereas peak pulsed power of 26 mW at 5 K was detected from a 4.1 THz laser without the lens (device Tmax = 165 K), the detected power increased to 145 mW with the lens with only a 5 K degradation in the maximum operating temperature (device Tmax = 160 K).
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Sushil Kumar, Sushil Kumar, Alan W. M. Lee, Alan W. M. Lee, Qi Qin, Qi Qin, Benjamin S. Williams, Benjamin S. Williams, Qing Hu, Qing Hu, John L. Reno, John L. Reno, } "High-temperature and high-power operation of terahertz quantum-cascade lasers", Proc. SPIE 6909, Novel In-Plane Semiconductor Lasers VII, 69090I (29 January 2008); doi: 10.1117/12.768298; https://doi.org/10.1117/12.768298

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