JPS5624992A - Laser light output modulating method and semiconductor laser device - Google Patents

Abstract

PURPOSE:To modulate the laser output intensity passing through respective reflectors without inducing alleviating vibration by altering the value of light return ratio of a pair of light reflectors while retaining the product thereof constantly. CONSTITUTION:The net effective gain of a laser crystal active layer 10 is represented by G, and both end reflectors 11, 12 have respectively reflectivity R1, R2 and transmittivity T1, T2. When a light of intensity I0 is incident to the reflector 11, there can be obtained a transmitting output I1=T1I0 and the transmitting output of the reflector 12 is given by the equation: I2=R1exp(GL)T2I0. In normal oscillation the amplification in the active layer is equal to the attenuation owing to incomplete reflection, that is, R1R2exp(2GL)=1. Accordingly, there can be obtained I1/I2= R2<1/2>T1/R1<1/2>T2. That is, the excitation is retained constantly, the product R1R2 is retained constantly, the ratio R1/R2 is modulated to modulate the ratio I1/I2. Since the product R1R2 is constant, the resonator loss is not altered, and the total output I1+I2 is equal to constant, but the outputs of the respective end surfaces are modulated. If the resonator loss and the excitation intensity are constant, the total amount of the photons and the excitation carrier in the resonator is constant so that alleviating vibration is not inducted thereat.