Phased-locked window lasers

Abstract

A laser in which the central portion is provided with current pumping means consisting of an array of current confining stripe contacts to provide a multiple emitter active layer and the end sections of the laser are provided with transparent waveguides. The active layer of this laser can be abruptly stepped along the direction of light propagation, or provided with tapered end couplers, or in any other way made transparent, so that light escapes from the emitters of the active layer of the central portion of the laser into the transparent waveguides at the ends of the laser. The transparent waveguides are of a non-absorbing material of higher bandgap than the central active layer material, or of the same material but otherwise rendered transparent, so that the escaping light strikes the mirror facets and is reflected back, whereby a portion of the reflected light couples back into its emitter and provides the optical feedback for laser operation. Phase-locking is achieved because when the light from each emitter under each pumped stripe region emerges into the transparent waveguides, there is less or no lateral waveguiding, and therefore the light from each emitter diverges. Because of this divergence, when this light strikes the mirror facets, portions of the light from each emitter are reflected back into other adjacent emitters, thus phase-locking the laser output and making it highly collimated. Relative to conventional multi-emitter lasers, five to ten times higher output powers from the collimated beam are obtained, such increase in power occurring because the material at the laser mirror surface is transparent to the active region radiation and therefore is not damaged by the very intense light.