Semiconductor laser device having a diffraction grating on a light emission side

A method for providing light from a semiconductor device comprising:

• radiating light from an active layer of said semiconductor device;
• providing a light reflecting facet positioned on a first side of said active layer;
• providing a light emitting facet positioned on a second side of said active layer thereby forming a resonant cavity between said light reflecting facet and said light emitting facet;
• providing a partial diffraction grating having a predetermined length and positioned on a light emission side of said resonator;
• and
• selecting said predetermined length of said partial diffraction grating such that said semiconductor device emits a light beam having a plurality of longitudinal modes within a predetermined spectral width of an oscillation wavelength spectrum of the semiconductor device.

A semiconductor device comprising:

• means for radiating light;
• means for reflecting said radiated light positioned on a first side of said means for radiating light;
• means for emitting light positioned on a second side of said means for radiating light to thereby form a resonant cavity between said means for reflecting light and said means for emitting light;
• and
• means for selecting a portion of said radiated light to be emitted by said semiconductor laser device as an output light beam;
• and
• means for ensuring said output light beam has an oscillation wavelength spectrum having a plurality of longitudinal modes located within a predetermined spectral width of the oscillation wavelength spectrum.

A semiconductor laser module comprising:

• a semiconductor laser device comprising:
• an active layer configured to radiate light;
• a light reflecting facet positioned on a first side of said active layer;
• a light emitting facet positioned on a second side of said active layer thereby forming a resonant cavity between said light reflecting facet and said light emitting facet;
• and
• a partial diffraction grating having a predetermined length and positioned on a light emission side of said resonator, wherein said predetermined length of said partial diffraction grating is selected such that said semiconductor device emits a light beam having a plurality of longitudinal modes within a predetermined spectral width of an oscillation wavelength spectrum of the semiconductor device;
• and
• a wave guide device for guiding said laser beam away from the semiconductor laser device.

An optical fiber amplifier comprising:

• a semiconductor laser device comprising:
• an active layer configured to radiate light;
• a light reflecting facet positioned on a first side of said active layer;
• a light emitting facet positioned on a second side of said active layer thereby forming a resonant cavity between said light reflecting facet and said light emitting facet;
• and
• a partial diffraction grating having a predetermined length and positioned on a light emission side of said resonator, wherein said predetermined length of said partial diffraction grating is selected such that said semiconductor device emits a light beam having a plurality of longitudinal modes within a predetermined spectral width of an oscillation wavelength spectrum of the semiconductor device;
• and
• an amplifying fiber coupled to said semiconductor laser device and configured to amplify a signal by using said light beam as an excitation light.

A wavelength division multiplexing system comprising:a transmission device configured to provide a plurality of optical signals having different wavelengths;

• an optical fiber amplifier coupled to said transmission device and including a semiconductor laser device comprising:
• an active layer configured to radiate light;
• a light reflecting facet positioned on a first side of said active layer;
• a light emitting facet positioned on a second side of said active layer thereby forming a resonant cavity between said light reflecting facet and said light emitting facet;
• and
• a partial diffraction grating having a predetermined length and positioned on a light emission side of said resonator, wherein said predetermined length of said partial diffraction grating is selected such that said semiconductor device emits a light beam having a plurality of longitudinal modes within a predetermined spectral width of an oscillation wavelength spectrum of the semiconductor device;
• and
• a receiving device coupled to said optical fiber amplifier and configured to receive said plurality of optical signals having different wavelengths.

A Raman amplifier comprising:

• a semiconductor laser device comprising:
• an active layer configured to radiate light;
• a light reflecting facet positioned on a first side of said active layer;
• a light emitting facet positioned on a second side of said active layer thereby forming a resonant cavity between said light reflecting facet and said light emitting facet;
• and
• a partial diffraction grating having a predetermined length and positioned on a light emission side of said resonator, wherein said predetermined length of said partial diffraction grating is selected such that said semiconductor device emits a light beam having a plurality of longitudinal modes within a predetermined spectral width of an oscillation wavelength spectrum of the semiconductor device;
• and
• a fiber coupled to said semiconductor laser device and configured to carry a signal that is amplified based on said light beam being applied to said fiber.