Abstract: A DFB laser assembly including both a DFB laser device, with a buried heterostructure having a cavity length of 400 ?m, a differential resistance of 4?, an emission wavelength of 1550 nm, and a thermal resistance of 50K/watt or less, and a heat sink mounting the DFB laser device in a junction-down structure so that the DFB laser device has a wavelength/current coefficient at 5 picometers/milli-ampere or less.

Abstract: Disclosed is a distributed feedback semiconductor laser device having a resonator for oscillating a laser beam and a laser module which is provided with the semiconductor laser device. The semiconductor laser device comprises a diffraction grating, formed inside the resonator, for periodically changing only an extinction coefficient k or both a real refractive index n and the extinction coefficient k in a complex refractive index N expressed by N=n−ik where i is an imaginary unit. The resonator has a first facet having a first reflectance and a second facet opposite to the first facet and having a second reflectance. The first reflectance is smaller than the second reflectance and equal to or larger than 10%, preferably equal to or smaller than 20%.

Abstract: A semiconductor laser includes a resonant cavity with a cavity length, an active layer structure provided within the resonant cavity and configured to radiate light in an optical gain distribution having a peak wavelength, an embedding layer provided within the resonant cavity and having a refractive index, and a diffraction grating embedded within the embedding layer and having a bandgap wavelength and a refractive index, the diffraction grating configured to select an emission wavelength of the resonant cavity independently of the peak wavelength in the optical gain distribution of the active layer structure. The embedding layer and diffraction grating are configured to provide operational characteristics satisfying the relationship 0<&lgr;e−&lgr;g≦100 nm, where &lgr;e is the emission wavelength of the resonant cavity &lgr;g is the bandgap wavelength of the diffraction grating.

Abstract: A DFB Laser of buried hetero type with a lasing wavelength of 1550 nm, having on an InP substrate a laminated structure of an InP buffer layer, an active layer, a 200-nm-thickness InP spacer layer, a 240-nm-period diffraction grating made of a 20-nm-thickness GaInAsP layer, and an InP first cladding layer in which diffraction grating is buried. The peak wavelength &lgr;max of the optical gain distribution of the active layer is approximately 1530 nm. The bandgap wavelength of the diffraction grating is approximately 1510 nm. The laminated structure is etched into mesa stripes, on both sides of which are formed p/n-separated current blocking regions. Since the diffraction grating is formed of GaInAsP having &lgr;g of approximately 1510 nm, little absorption occurs at wavelengths around the lasing wavelength 1550 nm.

Abstract: A semiconductor laser device includes a semiconductor substrate, an active region formed on the semiconductor substrate and configured to radiate light having a predetermined wavelength range, and a wavelength selecting structure configured to select a first portion of the radiated light for emitting from the semiconductor laser device. An absorption region is located in a vicinity of the active region and configured to selectively absorb a second portion of the radiated light, and the first portion of the radiated light has a different wavelength than the second portion of the radiated light. The absorption region may be an integrated diffraction grating or a selective absorption region of the laser device. The semiconductor laser device may be used in an optical fiber amplifier such as a raman amplifier, a wavelength division multiplexing system, or a semiconductor laser module.

Abstract: A DFB laser assembly including both a DFB laser device, with a buried heterostructure having a cavity length of 400 &mgr;m, a differential resistance of 40&OHgr;, an emission wavelength of 1550 nm, and a thermal resistance of 50 K/watt or less, and a heat sink mounting the DFB laser device in a junction-down structure so that the DFB laser device has a wavelength/current coefficient at 5 picometers/milli-ampere or less.

Abstract: A semiconductor laser device having a semiconductor substrate, an active region formed on the semiconductor substrate and configured to radiate light having a predetermined wavelength range, a light reflecting facet and a light emitting facet positioned at opposing longitudinal ends of the active region to form a resonant cavity. A diffraction grating is positioned within the resonant cavity, and is configured to select a first portion of the radiated light for emitting from the semiconductor laser device, and an absorption region located in a vicinity of the active region and configured to selectively absorb a second portion of the radiated light, the first portion of the radiated light having a different wavelength than the second portion of the radiated light. The light emitting facet has a reflectivity value of aproximately in the range of 10%-30%.

Abstract: A semiconductor laser includes a resonant cavity with a cavity length, an active layer structure provided within the resonant cavity and configured to radiate light in an optical gain distribution having a peak wavelength, an embedding layer provided within the resonant cavity and having a refractive index, and a diffraction grating embedded within the embedding layer and having a bandgap wavelength and a refractive index, the diffraction grating configured to select an emission wavelength of the resonant cavity independently of the peak wavelength in the optical gain distribution of the active layer structure. The embedding layer and diffraction grating are configured to provide operational characteristics satisfying the relationship 0<&lgr;e−&lgr;g≦100 nm, where &lgr;e is the emission wavelength of the resonant cavity &lgr;g is the bandgap wavelength of the diffraction grating.

Abstract: Disclosed is a distributed feedback semiconductor laser device having a resonator for oscillating a laser beam and a laser module which is provided with the semiconductor laser device. The semiconductor laser device comprises a diffraction grating, formed inside the resonator, for periodically changing only an extinction coefficient k or both a real refractive index n and the extinction coefficient k in a complex refractive index N expressed by N=n−ik where i is an imaginary unit. The resonator has a first facet having a first reflectance and a second facet opposite to the first facet and having a second reflectance. The first reflectance is smaller than the second reflectance and equal to or larger than 10%, preferably equal to or smaller than 20%.

Abstract: A semiconductor laser device includes a semiconductor substrate, an active region formed on the semiconductor substrate and configured to radiate light having a predetermined wavelength range, and a wavelength selecting structure configured to select a first portion of the radiated light for emitting from the semiconductor laser device. An absorption region is located in a vicinity of the active region and configured to selectively absorb a second portion of the radiated light, and the first portion of the radiated light has a different wavelength than the second portion of the radiated light. The absorption region may be an integrated diffraction grating or a selective absorption region of the laser device. The semiconductor laser device may be used in an optical fiber amplifier such as a raman amplifier, a wavelength division multiplexing system, or a semiconductor laser module.

Abstract: A DFB Laser of buried hetero type with a lasing wavelength of 1550 nm, having on an InP substrate a laminated structure of an InP buffer layer, an active layer, a 200-nm-thickness InP spacer layer, a 240-nm-period diffraction grating made of a 20-nm-thickness GaInAsP layer, and an InP first cladding layer in which diffraction grating is buried. The peak wavelength &lgr;max of the optical gain distribution of the active layer is approximately 1530 nm. The bandgap wavelength of the diffraction grating is approximately 1510 nm. The laminated structure is etched into mesa stripes, on both sides of which are formed p/n-separated current blocking regions, Since the diffraction grating is formed of GaInAsP having &lgr;g of approximately 1510 nm, little absorption occurs at wavelengths around the lasing wavelength 1550 nm.