Room-temperature lasing characteristics of bend and branch in photonic crystal waveguide

This paper describes semiconductor lasers that utilize bends and branches in a photonic crystal line defect waveguide as microcavities. Although the bends and branches are not completely surrounded by photonic crystal mirrors, they maintain a well-localized resonant mode as in a closed microcavity. In an experiment, devices fabricated into a GaInAsP slab were photopumped under a pulsed condition at room temperature, and lasing was observed with a threshold irradiated power of 1.0-2.5 mW. It was also observed in the experiment and a theory that lasing wavelengths at the bends and the branch are longer than those at a straight waveguide. This result indicates that the bends and the branch resonate at a cutoff frequency, while the straight waveguide resonates at the photonic band-edge.