GaAs-based quantum cascade lasers for the 5-6 THz range

There have been only few reports of THz QC-lasers operating over 5 THz, and none operating in CW mode. As the laser frequency increases, it approaches the Reststrahlen band (8-9 THz in GaAs) which increases the optical losses and degrades the gain. Here, we discuss design strategies to improve operating temperature for THz QCLs targeting 5.3-5.6 THz. These strategies are investigated numerically using a Non-equilibrium Green's Function solver. We demonstrate a metal-metal waveguide emitting in 4.76 – 6.03 THz with pulsed and CW operating temperature of 117 K and 68 K, respectively, and modes up to 5.71 THz in CW mode.