Publications

Focusing metasurface quantum-cascade laser with a near diffraction-limited beam

Xu, Luyao; Chen, Daguan; Itoh, Tatsuo; Reno, J.L.; Williams, Benjamin S.

A terahertz vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated using an active focusing reflectarray metasurface based on quantum-cascade gain material. The focusing effect enables a hemispherical cavity with flat optics, which exhibits higher geometric stability than a plano-plano cavity and a directive and circular neardiffraction limited Gaussian beam with M2 beam parameter as low as 1.3 and brightness of 1.86 � 106 Wsr-1m-2. This work initiates the potential of leveraging inhomogeneous metasurface and reflectarray designs to achieve high-power and high-brightness terahertz quantum-cascade VECSELs.