| 摘要 |
PROBLEM TO BE SOLVED: To enable a semiconductor laser device to keep a laser beam stable in output and wavelength at the same time by a method, wherein the level of a monitoring laser beam which passes through a band-pass filter and an optical filter which changes in transmission loss in one direction with a change in the wavelength of a laser beam is detected. SOLUTION: A semiconductor laser device 1, a first temperature detector 9, and an electronic cooler 7 are provided, and a first turnout 18 branches off a first branching laser beam from an oscillation laser beam. A first optical filter 20 transmits only a laser beam of prescribed wavelength band to output a first monitoring laser beam 23, and the level of the monitoring laser beam 23 is detected by a level detector 24. A second turnout 29 branches off a second branching laser beam from the oscillation laser beam, and a second optical filter 30 transmits the second branching laser beam so as to increase or decrease it in transmission loss in one direction with a change in wavelength to output a second monitoring laser beam 31, and the level of the second monitoring laser beam 31 is detected by a level detector 32. Furthermore, the level of a third monitoring laser beam branching off from the oscillation laser beam is detected by a level detector 33. |
