JPS6425587A - Integrated semiconductor laser - Google Patents

Abstract

PURPOSE:To detect and control oscillation frequency in a simple composition and to obtain stable laser oscillation beams of a small spectral line width by integrating an external oscillator-type semiconductor laser, optical waveguides and a pin photo diode on one and the same substrate. CONSTITUTION:The laser is composed of an n-type InP substrate 1, an active region 2 including an n-type InGaAsP active layer, a non-active region 3 including an n-type InGaAsP wavelayer, an optical waveguide 4 including an n-type InGaAsP wave layer and a pin photo diode 5 including an n-type InGaAsP active layer. End surfaces 9 and 10 constitute a laser oscillator and the non-active region 3 and the optical waveguide 4 constitute a directional coupler. The radiant power in the active region 2 oscillates by a oscillator of edge surfaces of 9 and 10 and the output power is obtained from the edge surface 9. A part of the radiant power 12 and 13 couples with the optical waveguide 4 each at a different optical guide and then is sensed by the pin photo diode. The sensitive power output is fed back to an electrode 7 of the non-active region of the semiconductor laser through a control circuit 11. Because the external oscillator is thus monolithic integrated, mechanical stability is realized maintaining a small spectral line width.