Abstract: A surface-emitting semiconductor laser device having reduced device resistance, a method for fabricating the device and a surface-emitting semiconductor laser array employing the device are provided. The laser device comprises a lower reflector layer structure and an upper reflector layer structure, formed on a p-type semiconductor substrate. An etching blocking layer, a current confinement layer, and an active layer are formed in that order from below between the lower and upper reflector layer structures. The portion over the etching blocking layer is formed into a mesa shape.

Abstract: A semiconductor laser device (30) includes a layered structure formed on an n-type GaAs substrate (32) having a bandgap energy Eg1 and including an n-type AlGaAs cladding layer (34), an active layer (36) including a quantum-well structure of two layers InGaAs/GaAs having a bandgap energy Eg2 which is smaller than Eg1, a p-type AlGaAs cladding layer (38), and a p-type GaAs cap layer (40), which are consecutively epitaxially grown. The cap layer and the upper portion of the p-type cladding layer are formed as a stripe-shaped mesa structure. An SiN passivation film (42) is formed on the areas except for the top of the cap layer. On the exposed cap layer and the passivation layer a p-side electrode (44) is formed. On the bottom surface of the substrate an n-side electrode (46) including layered metal films of In/AuGe/Ni/Au is formed. An absorption medium layer is interposed between the GaAs substrate and the n-side electrode.

Abstract: Provided is a ridge waveguide type semiconductor laser device in which fundamental transverse mode operation is stabilized and unstable jumps of a longitudinal mode (oscillation wavelength) never occur even with use of high optical output of 300 mW or more. The semiconductor laser device has a stacked structure composed of a substrate and layers thereon. The layers include a lower cladding layer, lower optical confinement layer, active layer, upper optical confinement layer, and upper cladding layer, which are built up in the order named. A ridge is formed on the upper cladding layer. The width (W) of the bottom ridge portion of the ridge ranges from 2.5 &mgr;m to 5.0 &mgr;m, and the distance from the bottom ridge portion to an active layer is adjusted to a value higher than 0.5 &mgr;m and not higher than 0.8 &mgr;m.

Abstract: An EA-DFB module including a DFB laser diode and an EA modulator formed on an InP first-conductivity-type substrate has a mesa stripe, a current blocking structure formed on both side surfaces of the mesa strip and a second InP cladding layer formed on top of the mesa stripe and the current blocking structure. The current blocking structure includes a Fe-doped semi-insulating film, a first conductivity-type buried layer and a carrier-depleted layer. The carrier-depleted layer reduces the parasitic capacitance at the boundary between the first-conductivity-type buried layer and the second InP cladding layer.

Abstract: A gain-coupled DFB semiconductor laser device has a resonator and a diffraction grating which feeds-back the emission from the resonator to increase wavelength selectively. The gain-coupled coefficient &kgr;g and the length Lg of the diffraction grating satisfy the following relationship: 0.5≦|&kgr;g|×Lg≦1.1. The yield rate of the DFB laser device with respect to the single-longitudinal mode lasing characteristic is improved.

Abstract: A self-aligned type semiconductor laser device which is capable of oscillation at high optical output, scarcely develops COMD, and maintains high reliability for a long term. The SAS type semiconductor laser device has an active layer, and a low refractive-index layer formed close the active layer and functioning also as a current blocking layer. The low refractive-index layer includes a plurality of compound semiconductor layers made of AlxGa1−xAs (0≦x≦1), and the compound semiconductor layers have refractive indices thereof set such that the refractive index lowers with increasing distance from the active layer. Specifically, the low refractive-index layer includes a plurality of AlGaAs layers, and the AlGaAs layers have contents of Al thereof set such that the content of Al increases with increasing distance from the active layer.

Abstract: Disclosed are a gain coupled distributed feedback type semiconductor laser device which has a high single-mode yield and a smaller variation in the oscillation threshold current and luminous efficiency, and a method of manufacturing the same. The semiconductor laser device has a gain or loss which periodically changes, and comprises a cavity; and a diffraction grating formed in the cavity in such a way that an absolute value of a gain coupling coefficient in a vicinity of at least one of facets of the cavity is smaller than an absolute value of a gain coupling coefficient in the other area.

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 distributed feedback semiconductor laser device including an active layer, a diffraction grating disposed in a vicinity of the active layer and having a substantially uniform space period and a distributed feedback function, and a functional layer disposed in a vicinity of the diffraction grating and the active layer and having a function of controlling a refractive index of the active layer, whereby the functional layer controls a lasing wavelength of the active layer. The functional layer of controlling the refractive index of the distributed feedback semiconductor laser device can generate a plurality of the lasing wavelengths different among one another and easily controllable.

Abstract: A GaAs based semiconductor laser has a combination of cladding layers including a ridge structure part, and a remaining part which overlays the active layers of the laser, and an etch stop layer sandwiched between the ridge structure part and the remaining part. The remaining part preferably overlies the entire surface of laser active layers and has a thickness “D” which satisfies 1.1×W>D≧0.5×W wherein W is the width of a spot size having a strength of {fraction (1/e2)} as measured at the laser front facet in a direction perpendicular to the active layers, wherein “e” is the base of the natural logarithm. The semiconductor laser solves the kink phenomenon to obtain an excellent linear relationship between the optical output power and the injected current.

Abstract: A quantum confinement Stark effect (QCSE) optical modulator has a ridge stripe including a current confinement structure. The current confinement structure includes an AlInAs layer which is subjected to selective oxidation of Al content in the AlInAs layer. The current confinement structure is such that a pair of Al-oxidized regions of the AlInAs layer sandwiches therebetween a central un-oxidized region.

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 GaAs based semiconductor laser has a combination of cladding layers including a ridge structure part and a remaining part sandwiching therebetween an etch stop layer. The remaining part overlies the entire surface of laser active layers and has a thickness “D” which satisfies D≧W×0.5 wherein W is the width of a spot size having a strength of 1/e2 for a near field pattern in the active layer in a direction perpendicular to the active layer, wherein “e” is the bottom of the natural logarithm.

Abstract: A semiconductor light emitting device including a semiconductor substrate and an active layer having band gap energy smaller than that of the active layer, and the bottom surface of the semiconductor substrate opposite to the active layer is a photo diffused reflection surface having unevenness. The unevenness reduces an amount of reflection rays to enable the stable operation.

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 process of producing a semiconductor layer structure which emits lights with a plurality of luminescence wavelengths from the same quantum well structure. The layer structure has a layer structure which has the quantum well structure located between a lower light-confinement layer and an upper light-confinement layer. At least a part of the quantum well structure is an area which has a shorter luminescence wavelength than those of the other portions. This area is produced by stacking a lower cladding layer, the lower light-confinement layer, the quantum well structure, the upper light-confinement layer and a first semiconductor layer having a first conductivity type on a semiconductor substrate by epitaxial growth and further stacking a second semiconductor layer having the opposite conductivity type to that of the first semiconductor layer on the entire surface or a partial surface of the first semiconductor layer. This second semiconductor layer may be removed after the formation.

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.