Room-temperature GaN vertical-cavity surface-emitting laser operation in an extended cavity scheme

A GaN-based vertical-cavity surface-emitting laser (VCSEL) has been demonstrated in an extended cavity structure. A VCSEL device had a long extended cavity, which consisted of a sapphire substrate as well as a GaN epilayer and had an integrated microlens on one side. High-reflection dielectric mirrors were deposited on both sides of the laser cavity. The laser was optically pumped and operated at room temperature. The VCSEL device lased at a low threshold excitation intensity of $\text{160\hspace{0.17em}}{\mathrm{kW/cm}}^2.$ In contrast to a conventional microcavity-VCSEL structure, the VCSEL operated in multiple longitudinal modes with mode spacing consistent with its physical thickness.