Semiconductor ring and folded cavity lasers

Abstract

A semiconductor laser that includes at least one grating reflector with a grating period selected to diffract at a nonperpendicular angle within the plane of the laser waveguide. This allows dispersal of laser light, eliminating filamentary multimode operation of broad area lasers. In one embodiment, the grating reflector couples light between a single transverse mode waveguide portion of the optical cavity and a second, broad area, portion that is not collinear with the single mode waveguide. In another embodiment, the cavity favors a ring mode of oscillation. One or more grating reflectors form part of the feedback mechanism which forms a resonant optical cavity with noncollinear portions. Other reflectors in the feedback mechanism include facet reflectors which can be cleaved or ion milled, or semiconductor material refractive index boundaries. Laser embodiments with two or more grating reflectors can be independently tuned to provide a high rate of amplitude modulation. Spatial beam deflection and wavelength tuning are also achieved. A stable unidirectional ring laser is also described. Multiple ring laser cavities can also be coupled together by partially reflecting grating reflectors to form a laser array.