UCLA

We report a twofold increase in slope efficiency of a terahertz quantum-cascade vertical-external-cavity surface-emitting laser enabled by an all-dielectric high-contrast grating output coupler (OC). In contrast to a conventional metal-mesh OC on a quartz substrate, the dielectric grating eliminates losses associated with the metal. The device operates in pulsed and continuous-wave modes, with threshold current and maximum operating temperature comparable to those of the quartz-based OC. A circular beam pattern is maintained across the full tuning bandwidth.