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 3dB bandwidth of the gain of the semiconductor laser or a spectrum full width at half maximum of the laser light of the semiconductor laser.

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.

Abstract: A semiconductor laser device comprises 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.

Abstract: A semiconductor laser device comprises 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.

Abstract: In an optical isolator, a laser beam is incident on a polarizer inclined by an inclined placement angle ranging from 50 to 60 degrees with respect to an optical axis, a polarized component of the laser beam polarized in a first polarization direction is transmitted through the polarizer. The polarized component of the laser beam is rotated by 45 degrees around the optical axis in a Faraday rotator, and the polarized component of the laser beam polarized in a second polarization direction is output. The polarized component of the laser beam is incident on an analyzer inclined by the inclined placement angle in a direction opposite to that of the inclination of the polarizer with respect to the optical axis. The analyzer has a polarized beam transmission characteristic to transmit only a laser beam polarized in the second polarization direction. Therefore, the polarized component of the laser beam transmitted from the Faraday rotator is transmitted through the analyzer almost without attenuation.

Abstract: A laser beam is incident on a polarizer inclined by an inclined angle ranging from 50 to 60 degrees with respect to an optical axis, a polarized component of the laser beam polarized in a first polarization direction passes through the polarizer. The polarized component is rotated on the optical axis in a second polarization direction by 45 degrees in a Faraday rotator and is incident on an analyzer which is inclined by the inclined angle in a direction opposite to that of the inclination of the polarizer with respect to the optical axis to transmit only a laser beam polarized in the second polarization direction. Therefore, the polarized component passes through the analyzer almost without attenuation, and a wave front aberration of the laser beam caused by the polarizer is cancelled out in the analyzer.