Semiconductor laser device and optical fiber amplifier

Abstract

A semiconductor laser device includes an optical fiber having an optical fiber grating formed therein, a semiconductor laser having an active layer with a single quantum well, for emitting laser light, and a coupling optical system for coupling the laser light emitted out of the semiconductor laser into the optical fiber. The coupling optical system can include a narrow-band filter for adjusting an incident angle of the laser light emitted out of the semiconductor laser. The optical fiber grating can have a reflection bandwidth wider than or substantially equal to a 3 dB bandwidth of the gain of the semiconductor laser or a spectrum full width at half maximum of the laser light of the semiconductor laser.

1 . An amplifier for an optical fiber comprising: 
 a semiconductor laser device including an optical fiber having an optical fiber grating, a laser diode having a plurality of layers including an active layer with a single quantum well, for emitting pumping light, another laser device for emitting signal light and a coupling optical system for coupling the pumping light emitted out of the laser diode into the optical fiber;    a pumping light-signal light coupling means for coupling the pumping light emitted out of the semiconductor laser device to the signal light; and    a rare-earth-doped optical fiber that is pumped by the pumping light so as to amplify the signal light output from the pumping light-signal light coupling means.    
     
     
         2 . An amplifier for an optical fiber comprising: 
 a semiconductor laser device including an optical fiber having an optical fiber grating, a laser diode having a plurality of layers including an active layer with two or more quantum wells formed at intervals that are close enough to provide quantum coupling, for emitting pumping light, another laser device for emitting signal light, and a coupling optical system for coupling the pumping light emitted out of the laser diode into the optical fiber;    a pumping light-signal light coupling means for coupling the pumping light emitted out of the semiconductor laser device to the signal light; and    a rare-earth-doped optical fiber that is pumped by the pumping light so as to amplify the signal light output from the pumping light-signal light coupling means.    
     
     
         3 . The amplifier according to  claim 1 , wherein the optical fiber grating having a wavelength characteristic which maintains a constant emission wavelength of the laser diode.  
     
     
         4 . The amplifier according to claim  2 x, wherein the optical fiber grating having a wavelength characteristic which maintains a constant emission wavelength of the laser diode.