Gain engineering for terahertz quantum cascade lasers

• Applicant: Yuri Victorovich Flores, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 299273829

• Final Report Year: 2018

Final Report Abstract

We investigated and demonstrated of novel active region design strategies for the fabrication of terahertz quantum cascade lasers (THz QCLs) with high optical gain. Our investigation addressed several factors driving the laser gain including the design of laser levels, electron injection, electron extraction, and population inversion. The developed design strategies led to THz QCLs with suppressed electron leakage with improved maximum operating temperature (from 121 to 173 K). We further reported on a thermophotonic effect in THz QCLs, meaning that –contrary to common sense expectation– the electron leakage current can actually help to QCL performance, increasing gain. A similar effect has been identified for interface roughness scattering (IFR), which is assumed to be always negative for the laser performance. We investigated the impact of IFR in THz QCLs and proposed design strategies for interface roughness-engineered THz QCLs with increasing laser gain. High optical gain translated into better laser performance in terms of a high energy conversion efficiency, high light output power and high operation temperature of devices. All three aspects are crucial for the development of future technology and applications based on terahertz light sources.

Publications

• “Carrier leakage dynamics in terahertz quantum cascade lasers,” IEEE Journal of Quantum Electronics 53 (5), 8500508 (2017)
  Albo, Asaf & Flores, Yuri V.
  
• “Design considerations for λ ~ 3.0-3.5 µm-emitting quantum cascade lasers on metamorphic buffer layers,” Optical Engineering 57 (1), 011017 (2017)
  Rajeev, Ayushi; Sigler, Chris; Earles, Tom & Flores, Yuri V.
  
• “High internal efficiency mid-IR quantum cascade lasers,” Proceedings of the 14th International Conference on Intersubband Transitions in Quantum Wells (ITQW, 2017)
  D. Botez, J. D. Kirch, C. Boyle, K. Oresick. C. Sigler, D. Lindberg, T. Earles, L. J. Mawst and Y. V. Flores
  
• “Impact of interface roughness scattering on the performance of GaAs/AlxGa1-xAs terahertz quantum cascade lasers,” IEEE Journal of Quantum Electronics 53 (3), 2300208 (2017)
  Flores, Yuri V. & Albo, Asaf
  
• “Temperature-driven enhancement of the stimulated emission rate in terahertz quantum cascade lasers,” IEEE Journal of Quantum Electronics 53 (1), 2300105 (2017)
  Albo, Asaf & Flores, Yuri V.
  
• “Two-well terahertz quantum cascade lasers with suppressed carrier leakage,” Applied Physics Letters 111, 111107 (2017)
  Albo, Asaf; Flores, Yuri V.; Hu, Qing & Reno, John L.
  
• “High-efficiency, high-power mid-infrared quantum cascade lasers”. Optical Materials Express 8 (5), 1378 (2018)
  Botez, Dan; Kirch, Jeremy D.; Boyle, Colin; Oresick, Kevin M.; Sigler, Chris; Kim, Honghyuk; Knipfer, Benjamin B.; Ryu, Jae Ha; Lindberg, Don; Earles, Tom; Mawst, Luke J. & Flores, Yuri V.