Semiconductor laser unit having a function of stabilizing an optical

Abstract

A semiconductor laser unit includes a semiconductor laser device, a first temperature detector that detects a temperature in the vicinity of the semiconductor laser device, and an electronic cooler that heats or cools the semiconductor laser device. The semiconductor laser unit also includes first and second branching devices for extracting first and second branched lights from an oscillation light outgoing from the semiconductor laser device, a band pass filter that transmits only a light of a predetermined wavelength band among the first branched light, and an optical filter that transmits the second branched light so that a transmission loss is increased or decreased in one way with a change of the wavelength within a wavelength band where the oscillation wavelength of the semiconductor laser device can be changed, to output a second monitor light. The levels of lights which transmit each wavelength are transmitted are detected, respectively, and when the level of light that passes through the band pass filter is increased, a direction of changing the wavelength is detected according to an increase or decrease of the level of light that passes through the optical filter, and the temperature is changed by the electronic cooler to control the wavelength of the semiconductor laser device. Thus, both of the output level and the wavelength of the oscillation light from the semiconductor laser are stabilized.