Abstract: An optical waveguide has a semiconductor laser section, an intermediate section, and an optical modulator section on a surface of a substrate. The distance of a surface extending outwardly from and transverse to both sides of a mesa stripe in the semiconductor laser section from the surface of the substrate is larger than the distance of a surface extending outwardly from and transverse to both sides of the mesa stripe in the optical modulator section from the surface of the substrate. The distance of a surface extending outwardly from and transverse to both sides of the mesa stripe in the intermediate section from the surface of the substrate decreases from the semiconductor laser section toward the optical modulator section.

Abstract: Provided is a photodiode array that is capable of outputting an electric signal with a large electric power and an optical microwave transmission system receiver that supplies an electric power with the aid of an optical fiber and does not require the electric power line from the external. An input modulation light is branched and input to a plurality of photodiode elements (1), electric output terminals (5) of the plurality of photodiode elements (1) are connected in parallel to each other, and a combined electric output is extracted. The electric output terminal (5) of the photodiode array configured as described above is connected to an antenna (7) without an intermediation of an amplifier circuit.

Abstract: A semiconductor laser comprises an active section for generating light, and a peripheral section as resonator for producing laser light from the generated light, and includes an InP substrate. The active section has a lower cladding layer formed of AlInAs or AlGaInAs, a core layer including an active layer formed of AlGaInAs or InGaAsP, and an upper cladding layer formed of AlInAs or AlGaInAs. The peripheral section has a first cladding layer formed by oxidizing AlInAs or AlGaInAs, a core layer, and a second clad layer formed by oxidizing AlInAs or AlGaInAs, and a two-dimensional photonic crystal defined by an array of regularly spaced apart holes the peripheral section.

Abstract: An optical wavelength converter includes: a first branch passage and a second branch passage receiving direct current light, one of the first branch passage and the second branch passage receiving input signal light; wavelength converting semiconductor optical amplifiers inserted into the first branch passage and the second branch passage, respectively; and a signal amplifying semiconductor optical amplifier for amplifying the input signal light, which is coupled with a port through which the input signal light is input to one of the first branch passage and the second branch passage. In the optical wavelength converter, differential gain of the signal amplifying semiconductor optical amplifier at a wavelength of the input signal light is less than differential gain of the wavelength converting semiconductor optical amplifier at the wavelength of the direct current light.

Abstract: An optical waveguide has a semiconductor laser section, an intermediate section, and an optical modulator section on a surface of a substrate. The distance of a surface extending outwardly from and transverse to both sides of a mesa stripe in the semiconductor laser section from the surface of the substrate is larger than the distance of a surface extending outwardly from and transverse to both sides of the mesa stripe in the optical modulator section from the surface of the substrate. The distance of a surface extending outwardly from and transverse to both sides of the mesa stripe in the intermediate section from the surface of the substrate decreases from the semiconductor laser section toward the optical modulator section.

Abstract: In a refractive index coupling distributed semiconductor laser having a ?/2-phase-shift distributed feedback structure with a diffraction grating having a refractive index coupling property on an active layer, when viewed in a light distributed feedback direction, a value of (duty of a high refractive index portion)/(duty of a low refractive index portion) of a diffraction grating in a rear end face region is larger than that of a diffraction grating in a front end face region. In this manner, a coupling coefficient ?2 in a front end face region of a conventional semiconductor laser is smaller than a coupling coefficient ?1 in a rear end face region and is larger than 100 cm?1.

Abstract: An optical wavelength converter includes: a first branch passage and a second branch passage receiving direct current light, one of the first branch passage and the second branch passage receiving input signal light; wavelength converting semiconductor optical amplifiers inserted into the first branch passage and the second branch passage, respectively; and a signal amplifying semiconductor optical amplifier for amplifying the input signal light, which is coupled with a port through which the input signal light is input to one of the first branch passage and the second branch passage. In the optical wavelength converter, differential gain of the signal amplifying semiconductor optical amplifier at a wavelength of the input signal light is less than differential gain of the wavelength converting semiconductor optical amplifier at the wavelength of the direct current light.

Abstract: A distributed feedback semiconductor laser includes an n-InP substrate, an n-InGaAsP diffraction grating layer above the n-InP substrate, an AlGaInAs-MQW active layer above the diffraction grating layer and a ridge portion on the active layer. The ridge portion includes a p-InP cladding layer and a p-InGaAs contact layer. The wavelength ?g corresponding to the bandgap energy of the diffraction grating layer and the oscillation wavelength ? of laser light produced by the laser satisfy the relationship ??150 nm<?g<?+100 nm.

Abstract: An n-InP second upper cladding layer is laid on a p-InP lower cladding layer while an active layer having upper and lower boundary surfaces that are uniformly flat in an optical waveguide direction is interposed therebetween. A diffraction layer having a phase-shifted structure provided in the direction of optical waveguide is interposed between the lower cladding layer and the active layer, or between the second upper cladding layer and the active layer. The length L of the diffraction grating layer in the direction of the optical waveguide is taken as L?260 ?m; a mean coupling factor ? of a diffraction grating layer is taken as ??130 cm?1; and ?L satisfies 5.6>?L>3.0.

Abstract: An n-InP second upper cladding layer is laid on a p-InP lower cladding layer while an active layer having upper and lower boundary surfaces that are uniformly flat in an optical waveguide direction is interposed therebetween. A diffraction layer having a phase-shifted structure in the optical waveguide direction is interposed between the lower cladding layer and the active layer or between the second upper cladding layer and the active layer. The length L of the diffraction grating layer in the direction of the optical waveguide is L≦260 &mgr;m; a mean coupling factor &kgr; of a diffraction grating layer is &kgr;≧150 cm−1; and &kgr;L satisfies 5.6>&kgr;L>3.0.

Abstract: In a refractive index coupling distributed semiconductor laser having a &Lgr;/2-phase-shift distributed feedback structure having a diffraction grating having a refractive index coupling property on an active layer, when viewed in a light distributed feedback direction, a value of (duty of a high refractive index portion)/(duty of a low refractive index portion) of a diffraction grating in a rear end face region is set to be larger than that of a diffraction grating in a front end face region. In this manner, a coupling coefficient &kgr;2 in a front end face region of a conventional semiconductor laser is set to be smaller than a coupling coefficient &kgr;1 in a rear end face region and is set to be larger than 100 cm−1.

Abstract: An n-InP second upper cladding layer 22 is laid on a p-InP lower cladding layer 14 while an active layer 16 whose upper and lower boundary surfaces are uniformly flat in the direction of optical waveguide is interposed therebetween. A diffraction layer 20 having a phase-shifted structure provided in the direction of optical waveguide is interposed between the lower cladding layer 14 and the active layer 16, or between the second upper cladding layer 22 and the active layer 16. The length L of the diffraction grating layer 20 in the direction of an optical waveguide is taken as L≦260 &mgr;m; a mean coupling factor &kgr; of a diffraction grating layer is taken as &kgr;≧150 cm−1; and a value &kgr;L, which is the product of the length L and the mean coupling factor &kgr;, is taken as 5.6>&kgr;L>3.0.

Abstract: An optical module includes a substrate having an upper surface and a groove on the upper surface; an optical fiber having a core and an end facet, disposed in the groove of the substrate; an optical semiconductor device having an upper surface and a light interactive area on the upper surface optically coupled to the optical fiber; and a block having a side surface on which the optical semiconductor device is fixed and a lower surface perpendicular to the side surface. The optical semiconductor device is fixed onto the side surface of the block so that the distance from the light interactive area to the lower surface of the block is equal to the distance from the core of the optical fiber to the upper surface of the substrate; and the block is disposed on the substrate, with the lower surface contacting the upper surface of the substrate, so that the light interactive area is opposed to the end facet of the optical fiber.

Abstract: A method of manufacturing an optical semiconductor device including forming an optical waveguide on a substrate and forming an alignment mark on the substrate simultaneously with the optical waveguide. The alignment marks do not transmit infrared light and, when the substrate is mounted on an infrared transmissive submount, precise alignment can be achieved by observing transmitted light. Thus, the optical semiconductor device including the substrate is soldered at the desired location.

Abstract: A semiconductor laser chip according to the present invention comprises: a p-type InP substrate; an InGaAsP active layer (optical waveguide) formed on said substrate; a p-n-p InP block layer formed on said substrate; a contact layer formed thereupon; an insulating film formed on said contact layer; a front surface electrode formed on said insulating film; a pair of alignment marks formed at the same time of the optical waveguide; and a back surface electrode formed on said substrate. The alignment marks are formed from the same material, i.e., the same crystal as said optical waveguide. Accordingly, it is possible to improve precision of the relative position between said optical waveguide and said alignment marks.

Abstract: A semiconductor laser device includes: a substrate serving as a heat sink; a thermal buffer plate disposed on the surface of the substrate; a first semiconductor laser chip having first and second main surfaces and including a first light emitting point in the vicinity of the first main surface, the first semiconductor laser chip being disposed on the surface of the thermal buffer plate at the second main surface; spaced apart thermal conductors disposed on the first main surface of the first semiconductor laser chip spaced from the first light emitting point with the first light emitting point between them; a second semiconductor laser chip having third and fourth main surfaces and including a second light emitting point in the vicinity of the third main surface, the second semiconductor laser chip being disposed on the thermal conductors at the third main surface so that the light radiation direction of the second semiconductor laser chip is parallel to the light radiation direction of the first semiconduct

Abstract: In an optical modulator including a laser light source emitting laser light and a modulator, a modulation signal source for applying a modulation signal to the modulator, a signal processor for producing and outputting a signal in response to a change in the modulation signal, and a driving current source for generating a driving current applied to the laser light. Wavelength chirping modulation reverse to the wavelength chirping occurring in the modulator is produced in the light emitted from the laser by modulation of the driving current whereby wavelength chirping produced by the modulator is at least partially cancelled and wavelength chirping of the light output from the modulator is reduced.

Abstract: A semiconductor device having a semiconductor element and a heat sink radiating heat generated by the semiconductor element incudes an amorphous semiconductor film disposed on the heat sink and the semiconductor element disposed on the amorphous semiconductor film. Therefore, the stress applied to the semiconductor element is reduced because of the amorphous semiconductor film. In one structure, an amorphous semiconductor film comprising amorphous silicon or amorphous germanium is sandwiched between first and second metal films and the semiconductor element is bonded to the second metal film. An ohmic contact is made by alloys formed between the amorphous semiconductor film and the first and second metal films.

Abstract: A semiconductor optical device includes a semiconductor laser having an effective refractive index n.sub.c, a first film having a refractive index n.sub.1 and a thickness d.sub.1, a second film having a refractive index n.sub.2 and a thickness d.sub.2, and a third film having a refractive index n.sub.3 and a thickness d.sub.3. The first to third films are successively disposed on a facet of the semiconductor laser. In this structure, the refractive indices and thicknesses of the first to third films are determined so that a characteristic matrix Xa of the three films is equal to a characteristic matrix Y of a single film whose refractive index n.sub.f is the square root of the effective refractive index n.sub.c of the semiconductor laser and whose thickness is obtained by dividing an oscillation wavelength .lambda. of the semiconductor laser by 4n.sub.f as represented by the following equation ##EQU1## where .phi.1=2.pi.n.sub.1 d.sub.1 /.lambda., .phi.2=2.pi.n.sub.2 d.sub.2 /.lambda., and .phi.3=2.pi.n.sub.

Abstract: A semiconductor device having a semiconductor element and a heat sink radiating heat generated by the semiconductor element includes an amorphous semiconductor film disposed on the heat sink and the semiconductor element disposed on the amorphous semiconductor film. Therefore, the stress applied to the semiconductor element is reduced because of the amorphous semiconductor film. In one structure, an amorphous semiconductor film comprising amorphous silicon or amorphous germanium is sandwiched between first and second metal films and the semiconductor element is bonded to the second metal film. An ohmic contact is made by alloys formed between the amorphous semiconductor film and the first and second metal films.