Semiconductor laser device and driving method of the same

Abstract

A semiconductor laser device that outputs light while periodically varying the temperature of a semiconductor laser, an optical waveguide, or a diffraction grating, outputs light while causing the optical waveguide or the diffraction grating to mechanically and periodically vary, or causes return light, which varies periodically or non-periodically, to be incident on the semiconductor laser. Since the periodical fluctuation is applied to the temperature of the semiconductor laser, the optical waveguide, or diffraction grating, the periodical mechanical variation is applied to the optical waveguide or the diffraction grating, or the return light is caused to be incident on the semiconductor laser, the semiconductor laser carries out a multimode oscillation from a low output to a high output without shifting between a single mode oscillation and a multimode oscillation.

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         6 . A semiconductor laser device comprising:
 a semiconductor laser for generating light;   a diffraction grating optically coupled with the semiconductor laser for reflecting a part of light having a predetermined wavelength of the light from the semiconductor laser to the semiconductor laser;   an optical waveguide for optically coupling between the semiconductor laser and the diffraction grating; and   return light control causing return light whose light intensity or wavelength periodically or non-periodically varies to be incident on a portion of the semiconductor laser from which light is emitted.   
     
     
         7 . The semiconductor laser device according to  claim 6 , wherein the return light control causes the return light to be incident on the portion from which the light of the semiconductor laser is emitted through the diffraction grating. 
     
     
         8 . A semiconductor laser device comprising:
 a semiconductor laser for generating light;   a diffraction grating optically coupled with the semiconductor laser for reflecting a part of light having a predetermined wavelength of the light from the semiconductor laser to the semiconductor laser;   an optical waveguide for optically coupling between the semiconductor laser and the diffraction grating; and   vibration device applying a periodical mechanical variation to the optical waveguide or the diffraction grating.   
     
     
         9 . The semiconductor laser device according to  claim 8 , wherein the periodical fluctuation of the vibration device in the semiconductor laser device are in a sine wave state. 
     
     
         10 . The semiconductor laser device according to  claim 8 , wherein the vibration device is a piezoelectric element connected to the optical waveguide or the diffraction grating. 
     
     
         11 . The semiconductor laser device according to  claim 10 , wherein the periodical fluctuation of the vibration device in the semiconductor laser device is in a sine wave state. 
     
     
         12 . A driving method of a semiconductor laser device in which a semiconductor laser is optically coupled with a diffraction grating through an optical waveguide and a part of light having a predetermined wavelength of the light generated by the semiconductor laser is reflected to the semiconductor laser by the diffraction grating and the light having the predetermined wavelength is generated, comprising the steps of:
 outputting light while applying a periodical fluctuation to the temperature of the semiconductor laser, the diffraction grating or the optical waveguide,   applying a periodical mechanical variation to the optical waveguide or the diffraction grating or in the alternative causing return light whose light intensity or wavelength periodically or non-periodically varies to be incident on a portion of the semiconductor laser from which light is emitted.