| 摘要 |
PURPOSE:To stabilize the frequency of output light from a semiconductor laser to a high degree for a prolonged term, and to vary the frequency continuously by phase-modulating the output light by an output from an oscillator, projecting the phase-modulated output light to a Fabry-Perot interferometer and controlling the FM side-band of an output from the interferometer so as to coincide with one of the peaks of the transmitted light of the interferometer. CONSTITUTION:Output light from a semiconductor laser 20 is phase-modulated or frequency-modulated on the basis of an output from a highly stable oscillator 23 by a phase modulation means 22 or a frequency modulation means, the modulated light is projected to a Fabry-Perot interferometer 24, and the intensity of the transmitted light is detected by a photodetection means 27. The frequency of output light from the semiconductor laser 20 is controlled so as to coincide with one of the peaks of the intensity of the transmitted light of the Fabry-Perot interferometer 24 by a first control means 28. The FSR(Free Spectral Range) of the Fabry-Perot interferometer 24 is controlled in relation to an output from the oscillator 23 by a second control means 30. Accordingly, the frequency of output light can be changed continuously with excellent accuracy. |
