High-power 2.2 THz quantum-cascade laser with sixth-order distributed feedback

Abstract

A distributed-feedback (DFB) scheme with sixth-order Bragg gratings realizes high-power emission for low-frequency single-mode terahertz quantum-cascade lasers (QCLs). The gratings are implemented in top claddings of plasmonic metallic cavities of the QCLs with four appropriately placed radiating slits per period. A peak optical power of 112 mW is detected for a 2.2 THz surface-emitting QCL in a single-lobed beam at 59 K, with a maximum operating temperature of 97 K in pulsed-mode. Numerical modeling indicates that the DFB scheme allows for a large variation of the radiative loss by adjusting the slits, and hence may be suitable for different types of QCL active regions.