Effects of metasurface quality factor on RF injection locking in terahertz quantum cascade-VECSELs

Terahertz quantum-cascade vertical-external-cavity-surface-emitting-lasers (QC-VECSELs) consist of an amplifying QC metasurface and an output coupler (OC) mirror, a dielectric slab (typically silicon or quartz) patterned on one side with a metallic mesh. Strong RF modulation of the QC-VECSEL with a V-shaped cavity produced lasing bandwidths up to 330 GHz. In this work, we investigate the possibility of engineering the output coupler for dispersion control, while maintaining high reflectance and laser performance. Specifically, we will investigate the feasibility of using the output coupler as a Gires Tournois interferometer. GTI output couplers are designed for a QC-VECSEL with reflectance centered at 3.2 THz and lasing bandwidth of 100 GHz. We will report their effectiveness for dispersion compensation and effect on lasing bandwidth.