Design for Stable Lasing of an Indirect Injection THz Quantum Cascade Laser Operating at Less Than 2 THz

摘要

In order to realize high temperature lasing of low frequency (& 2 THz) terahertz quantum cascade lasers (THz QCLs), selective carrier injection into an upper lasing level using an indirect injection (II) scheme is an effective method for inducing population inversion. The II scheme is realized with a four-level system. However, a three-level system that operates at low applied bias voltages causes additional lasing at higher frequencies (4～5 THz). By detuning the wave functions at the three lasing levels operating at low bias voltages, we were able to operate an II scheme THz QCL at a single stable frequency. Utilizing the higher injection selectivity, achieved through an indirect scattering-assisted injection process combined with diagonal emission, we were able to demonstrate stable operation of an AlGaAs/GaAs QCL operating at 1.89 THz at temperatures up to 160 K.