JPS6410689A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser with a writing light source capable of causing self-excited oscillation stably and having low noise properties and with an optically reading light source capable of holding stable basic lateral mode oscillation and giving large optical output oscillation, by providing a first groove and a second groove which is wider than the first one in parallel with each other and longitudinally to a resonator of a semiconductor substrate having a PN junction. CONSTITUTION:Current supplied from an electrode flows throughout a P-type GaAs substrate 10 but is blocked by an N-type GaAs layer 11 adjacent to the substrate 10. The current therefore flows through a resonator central region defined by first and second grooves 11, 12 extending from the layer 11 up to the substrate 10. The current then flows through a P-type Al0.45Ga0.55As first clad layer 14 and a P-type guide layer 15 and enters into a multiple quantum well active layer 16. Carriers injected into the layer 16 are diffused horizontally or transversely through the active layer to provide gain distribution, and oscillation of the laser is started. Since current is injected into the active layer through the respective grooves 12 and 13, little current flows into Si diffused regions 19, 20 near the reflecting surfaces. Accordingly, a propor tion of current which becomes invalid is very low.