Abstract: A semiconductor optical device includes an SOI substrate having a waveguide of silicon, and at least one gain region of a group III-V compound semiconductor having an optical gain bonded to the SOI substrate. The waveguide has a bent portion and multiple linear portions extending linearly and connected to each other through the bent portion. The gain region is disposed on each of the multiple linear portions.

Abstract: A semiconductor optical device includes an SOI substrate having a waveguide of silicon, and at least one gain region of a group III-V compound semiconductor having an optical gain bonded to the SOI substrate. The waveguide has a bent portion and multiple linear portions extending linearly and connected to each other through the bent portion. The gain region is disposed on each of the multiple linear portions.

Abstract: A laser apparatus for tuning the emission wavelength of a wavelength tunable laser diode will be described. The apparatus includes a tunable LD with heaters to tune the emission wavelength of the tunable LD, and a controller to control the power supplied to the heaters. A feature of the laser apparatus is that the controller supplies pre-emphasis power to the heaters before the supplement of the power corresponding to the re-tuned emission wavelength to accelerate the stability of the temperature of the heaters.

Abstract: A system includes: a splitter to branch an optical signal output by a wavelength-tunable light source into first to third optical signals; a first photodiode to perform an optical electrical conversion of the first optical signal transmitting a first etalon; a second photodiode to perform an optical electrical conversion of the second optical signal transmitting a second etalon, an FSR of the second etalon being identical to that of the first etalon, peak wavelengths of intensity of a transmitted light of the second etalon being different from those of the first etalon; a third photodiode to perform an optical electrical conversion of the third optical signal; and a controller to control the wavelength-tunable light source with use of a coefficient calculated by following formulas (1) or (2), Coefficient=(PD1?A·PD3)/(PD2?B·PD3) (1) and Coefficient=(PD2?B·PD3)/(PD1?A·PD3) (2).

Abstract: A laser apparatus for tuning the emission wavelength of a wavelength tunable laser diode will be described. The apparatus includes a tunable LD with heaters to tune the emission wavelength of the tunable LD, and a controller to control the power supplied to the heaters. A feature of the laser apparatus is that the controller supplies pre-emphasis power to the heaters before the supplement of the power corresponding to the re-tuned emission wavelength to accelerate the stability of the temperature of the heaters.

Abstract: A system includes: a splitter to branch an optical signal output by a wavelength-tunable light source into first to third optical signals; a first photodiode to perform an optical electrical conversion of the first optical signal transmitting a first etalon; a second photodiode to perform an optical electrical conversion of the second optical signal transmitting a second etalon, an FSR of the second etalon being identical to that of the first etalon, peak wavelengths of intensity of a transmitted light of the second etalon being different from those of the first etalon; a third photodiode to perform an optical electrical conversion of the third optical signal; and a controller to control the wavelength-tunable light source with use of a coefficient calculated by following formulas (1) or (2), Coefficient=(PD1?A·PD3)/(PD2?B·PD3) (1) and Coefficient=(PD2?B·PD3)/(PD1?A·PD3) (2).

Abstract: A wavelength tunable semiconductor laser includes: a first facet having reflectivity of 10% or more; a second facet; a wavelength selection portion between the first facet and the second facet; and an optical absorption region between the first facet and the wavelength selection portion. Another wavelength tunable semiconductor laser includes: a first facet having reflectivity of 10% or more to inside of the semiconductor laser; a second facet for output; a wavelength selection portion having diffraction gratings and positioned between the first and the second facet; an optical absorption region located between the first facet and the wavelength selection portion.

Abstract: A method of manufacturing a distributed feedback semiconductor laser, has the steps of: growing on a semiconductor substrate a lamination of alternately stacked lower barrier layer and lower well layer having a band gap narrower than the lower barrier layer, to form a lower quantum well structure; growing an intermediate layer on an uppermost lower well layer, the intermediate layer having a band gap broader than the lower well and a thickness thicker than the lower barrier layer; growing on the intermediate layer a lamination of alternately stacked upper well layer and upper barrier layer having a band gap broader than the upper well layer and a thickness thinner than the intermediate layer, to form an upper quantum well structure; forming a mask on the upper quantum well structure, the mask having periodical pattern; by using the mask as an etching mask, etching the upper quantum well structure in a periodical shape by using the intermediate layer as an etching margin layer; and removing the mask.

Abstract: A lower quantum well structure is formed extending along a resonator direction, the lower quantum well structure being formed by alternately stacking lower barrier layers and lower well layers having a band gap narrower than a band gap of the lower barrier layers. An intermediate layer is disposed over the lower quantum well structure. The intermediate layer has a band gap broader than the band gap of the lower barrier layers. An upper quantum well structure is periodically disposed over the intermediate layer along the resonator direction. The upper quantum well structure is formed by alternately stacking upper well layers and upper barrier layers having a band gap broader than a band gap of the upper well layers. A distributed feedback semiconductor laser is provided which is not likely to oscillate in the mode at a shorter wavelength and is likely to oscillate in the mode at a longer wavelength.

Abstract: An optical semiconductor element and an optical element having an optical coupling facet are disposed on a support surface of a platform. The optical element is optically coupled to the optical semiconductor element at the optical coupling facet. A protective member covers the optical semiconductor element and is disposed at least in a light transmission area in a space between the semiconductor element and the optical coupling facet of the optical element. The protective member is made of gel acrylic modification resin. An optical semiconductor module having a sufficient moisture resistance and being suitable for low cost is provided.

Abstract: A DFB laser in which a thickness of an active layer changes periodically and a greater part of current injected from external sides is selectively injected into the thick regions (projected regions) of the active layer. Therefore, the ratio of the gain coupling to the refractive index coupling can be further increased, and a threshold current can be lowered, and stability of single mode oscillation can also be improved.

Abstract: An optical semiconductor element and an optical element having an optical coupling facet are disposed on a support surface of a platform. The optical element is optically coupled to the optical semiconductor element at the optical coupling facet. A protective member covers the optical semiconductor element and is disposed at least in a light transmission area in a space between the semiconductor element and the optical coupling facet of the optical element. The protective member is made of gel acrylic modification resin. An optical semiconductor module having a sufficient moisture resistance and being suitable for low cost is provided.

Abstract: There is provided a semiconductor laser which comprises a first cladding layer formed of compound semiconductor having first conductivity type impurity and having a mesa-shaped projection, an active layer formed on the projection like a stripe and having side surfaces which are inclined at an angle of more than 70 degrees but less than 90 degrees relative to an upper surface of the first cladding layer, buried layers formed on both sides of the projection and having second conductivity type impurity, current blocking layers each having one end which contacts a virtual surface obtained by extending upward a side surface of the active layer and having a first facet which extends downward from the one end and is inclined by about 55 degrees relative to the upper surface of the first cladding layer and formed on each buried layer and having the first conductivity type impurity, and second cladding layers formed on the current blocking layers and the active layer and having the second conductivity type impurity.

Abstract: An optical semiconductor element and an optical element having an optical coupling facet are disposed on a support surface of a platform. The optical element is optically coupled to the optical semiconductor element at the optical coupling facet. A protective member covers the optical semiconductor element and is disposed at least in a light transmission area in a space between the semiconductor element and the optical coupling facet of the optical element. The protective member is made of gel acrylic modification resin. An optical semiconductor module having a sufficient moisture resistance and being suitable for low cost is provided.

Abstract: In a semiconductor light-emitting device including an MQW diffraction grating structure mainly used in a gain-coupled DFB laser, the ratio of the gain coupling coefficient to the index coupling coefficient is increased by making each well layer in MQW-A thicker than that in MQW-B. Each well layer and each barrier layer in the MQW structure are made of different compositions of GaInAsP. This implements a semiconductor light-emitting device with high wavelength stability, which does not induce any mode hop even during modulation with high output power or even when external optical feedback is present.

Abstract: A DFB laser in which a thickness of an active layer changes periodically and a greater part of current injected from external sides is selectively injected into the thick regions (projected regions) of the active layer. Therefore, the ratio of the gain coupling to the refractive index coupling can be further increased, and a threshold current can be lowered, and stability of single mode oscillation can also be improved.

Abstract: A method of manufacturing a distributed feedback semiconductor laser, has the steps of: growing on a semiconductor substrate a lamination of alternately stacked lower barrier layer and lower well layer having a band gap narrower than the lower barrier layer, to form a lower quantum well structure; growing an intermediate layer on an uppermost lower well layer, the intermediate layer having a band gap broader than the lower well and a thickness thicker than the lower barrier layer; growing on the intermediate layer a lamination of alternately stacked upper well layer and upper barrier layer having a band gap broader than the upper well layer and a thickness thinner than the intermediate layer, to form an upper quantum well structure; forming a mask on the upper quantum well structure, the mask having periodical pattern; by using the mask as an etching mask, etching the upper quantum well structure in a periodical shape by using the intermediate layer as an etching margin layer; and removing the mask.

Abstract: In a semiconductor light-emitting device including an MQW diffraction grating structure mainly used in a gain-coupled DFB laser, the ratio of the gain coupling coefficient to the index coupling coefficient is increased by making each well layer in MQW-A thicker than that in MQW-B. Each well layer and each barrier layer in the MQW structure are made of different compositions of GaInAsP. This implements a semiconductor light-emitting device with high wavelength stability, which does not induce any mode hop even during modulation with high output power or even when external optical feedback is present.

Abstract: A technique for manufacturing a semiconductor device includes the steps of preparing a stepped substrate made of a group III-V compound semiconductor and having a flat surface exposing a (1 0 0) plane and a slanted surface exposing an (n 1 1)B plane whrerein n is a real number of about 1.ltoreq.n, and epitaxially growing the group III-V compound semiconductor to form an epitaxial layer on the surface of the stepped substrate while doping p- and n-type impurities, selectively at the same time or, alternatively, under conditions such that the grown epitaxial layer has an n-type region on the slanted surface and a p-type region on the flat surface.

Abstract: A technique for manufacturing a semiconductor device includes the steps of preparing a stepped substrate made of a group III-V compound semiconductor and having a flat surface exposing a (1 0 0) plane and a slanted surface exposing an (n 1 1)B plane, wherein is a real number of about 1.ltoreq.n, and epitaxially growing the group III-V compounds semiconductor to form an epitaxial layer on the surface of the stepped substrate while doping p- and n-type impurities, selectively at the same time or, alternatively, under conditions such that the grown epitaxial layer has an n-type region on the slanted surface and a p-type region on the flat surface.