<title>Stable broad near-field (single-lateral mode) semiconductor laser</title>

Abstract

Single stripe gain-guided semiconductor lasers are generally fabricated with a stripe width limited to about 3 micrometers to obtain single lateral mode operation. For lasers with larger stripe widths, the carriers under the stripe induce index antiguiding that leads to near field instability. To improve on the stability of the near field, a number of quasi-index structures have been introduced such as the rib waveguide, ridge waveguide and the channeled substrate planar striped that make use of the evanescent field coupling to induce an effective lateral index step over the striped region. Quasi-index structures control only the optical field and for stripe widths larger than 5 micrometers , control of the carrier distribution becomes important as the optical field depletes the carriers leading to an inhomogeneous distribution that aids multi- lateral mode excitation. This paper presents a V-grooved stripe contact structure that preferentially channels the carrier to the center of the stripe as well as maintaining a stable carrier distribution induced by the V-groove contact. Such a laser has been successfully fabricated by liquid phase epitaxy and is able to emit in a single lateral mode with a FWHP of 20 micrometers at up to two times threshold current. The GaAlAs laser typically has an active layer of 0.1 micrometers , cladding layer thicknesses of 3 micrometers and a p-GaAs cap layer, 6 micrometers thick, with a flat-bottom V-groove etched into it. Power output of 20 mW is measured for this prototype.