A novel separate lateral confinement quantum well heterostructure laser

Abstract

Summary form only given. In the lateral dimension of a semiconductor laser, a single structure is usually used to confine both carriers and the optical mode, as in buried heterostructure (BH) or ridge waveguide (RW) lasers. The BH exhibits threshold current densities half that of RW lasers due to strong lateral carrier confinement. However, due to the large index step created by the lateral heterostructure, the BH must be made very narrow (typically <2 /spl mu/m) to cutoff propagation of undesired higher order lateral modes. A narrow device has several disadvantages including: a smaller available gain volume, higher optical power densities at the facets, larger diffraction angles of the emitted beam, and more stringent process control requirements. One proposal that has been successfully implemented to mitigate these problems is to flare the waveguide near the facet to allow the mode to expand laterally. In our specific implementation, the optical mode is confined by a 3.5 /spl mu/m etched ridge waveguide (RW), which is centered over a wider BH. The RW is used to make a wide single mode index guide, while the BH laterally confines the carriers.