An external cavity nonlinear quantum cascade laser with high mid-infrared to terahertz conversion efficiency in the frequency of 1.2-4.5 THz tuning range

A broadly tunable THz nonlinear QCLs with enhanced conversion efficiency by employing a homogeneous active region is demonstrated. Using an external cavity configuration, the device has achieved tunability from 1.2 THz to 4.5 THz in the operating frequency range. The single dual-upper-state structure with wide gain bandwidth and a high nonlinear susceptibility χ2 enables to realize two-wavelength oscillations without stacking active regions and significantly improves the mid-infrared to THz conversion efficiency, resulting in superior performance over previously reported frequency tunable devices. The device has achieved a conversion efficiency of ~3 mW/W2 around 3.5 THz. In the presentation, spectroscopic measurements using this device will also be reported.