Abstract

Recently, the possibility to integrate giant artificial nonlinearities into the quantum cascade laser (QCL) active region by appropriate quantum design has become highly attractive for various applications. In particular, THz difference frequency generation (DFG) has opened a door to compact, semiconductor-based THz sources operating at room temperature [1–4]. While conventional THz QCLs only work under cryogenic conditions, this approach takes advantage of the fact that efficient mid-infrared (MIR) QCLs for room temperature operation are readily available. THz DFG at a frequency f₁-f₂ is here achieved by using a dual-stack active region design with MIR lasing modes at f₁ and f₂ which pump a giant optical nonlinearity integrated into one or both active regions. An attractive feature is the inherent wide THz tuning capability, with a maximum demonstrated frequency range of 1.2–5.9 THz [2,3]. However, THz DFG structures still suffer from low room temperature THz output powers of up to 3 μW in continuous-wave and 1.4 mW in pulsed mode [4].

© 2015 IEEE