OUTPUT STABILIZING CIRCUIT FOR SEMICONDUCTOR LASER

PURPOSE:To stabilize the output of semiconductor laser by a method wherein a current detecting LED having an excellent temperature stabilizing property is provided on the circuit where the signal current same as laser runs, the detected value of the LED and that of the laser output are compared, and the bias current of the laser is controlled corresponding to the comparison output. CONSTITUTION:A light-emitting element 7 to be used for detection of signal current is arranged on the semiconductor laser 1 in series, and the light output of said light-emitting element 7 is detected by detecting the signal current IP running on the semiconductor laser 1. The current running on the laser 1 is formed as IP+IB based on the bias current IB consisting of a signal current IP and a bias control circuit 4, and this current runs on the light-emitting element 7. The light output corresponding to the signal current is detected by the light output detector 8, and added to the plus input of a differential amplifier 6 as a voltage signal EREF. Also, the light output F0 of the semiconductor laser 1 detected by the light output detector 2 is added to the minus input. The differential output is inputted to the bias control circuit 4, and the bias current IB of the laser 1 is stabilized.