Abstract: An optical modulation device includes: an optical splitter for splitting input light into a first input beam and a second input beam; an optical intensity modulator for modulating the intensity of the first input beam in response to a modulating signal; a variable optical phase shifter for shifting the phase of the second input beam; and an optical combiner for combining an output beam of the optical intensity modulator and an output beam of the variable optical phase shifter into a combined beam and outputting the combined beam. The amount of phase shift produced by the variable optical phase shifter is externally controlled.

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: An optical modulation device includes: an optical splitter for splitting input light into a first input beam and a second input beam; an optical intensity modulator for modulating the intensity of the first input beam in response to a modulating signal; a variable optical phase shifter for shifting the phase of the second input beam; and an optical combiner for combining an output beam of the optical intensity modulator and an output beam of the variable optical phase shifter into a combined beam and outputting the combined beam. The amount of phase shift produced by the variable optical phase shifter is externally controlled.

Abstract: A semiconductor laser device includes a semiconductor laser portion, a window layer structure portion, a first inter-element portion, and a pre-placed optical element portion on an InP substrate. The semiconductor laser portion includes an InGaAsP layer and an InP layer located on the InGaAsP layer. The window layer structure portion of a double heterojunction structure has the same optical axis direction as the semiconductor laser portion and is located apart from the semiconductor laser portion. The first inter-element portion has a 100-?m or less thickness in an optical axis direction, is in contact with an end face on a side of the window layer structure portion adjacent to the semiconductor laser portion and includes an InGaAsP layer and an InP layer of the same layer configuration as the semiconductor laser portion.

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: A semiconductor laser device includes a semiconductor laser portion, a window layer structure portion, a first inter-element portion, and a pre-placed optical element portion on an InP substrate. The semiconductor laser portion includes an InGaAsP layer and an InP layer located on the InGaAsP layer. The window layer structure portion of a double heterojunction structure has the same optical axis direction as the semiconductor laser portion and is located apart from the semiconductor laser portions. The first inter-element portion has a 100-?m or less thickness in an optical axis direction, is in contact with an end face on a side of the window layer structure portion adjacent to the semiconductor laser portion and includes an InGaAsP layer and an InP layer of the same layer configuration as the semiconductor laser portion.

Abstract: An optical modulator with lowered chirping without deterioration of extinction characteristic. An intermediate layer is interposed between a well layer and an n-side barrier layer and tensile strain is produced in the well layer. A relationship Ew<Em<Eb is established between a band gap energy Eb (eV) of the barrier layer, the band gap energy Ew (eV) of the well layer, and the band gap energy Em (eV) of the intermediate layer. Another type of tensile strain quantum well structure having four kinds of layers may be employed by adding another layer to the tensile strain quantum well structure having three layers. The band gap energy of an additional layer is between the band gap energies of the well layer and the intermediate layer or between the band gap energies of the intermediate layer and the barrier layer.

Abstract: A waveguide semiconductor optical device has a pin junction on a semi-insulating substrate. The pin junction consists of an n-type cladding layer, an i-type absorption layer, and a p-type cladding layer. The waveguide semiconductor optical device includes a dopant impurity concentration not higher than 1016 cm-3 in the i-type absorption layer.

Abstract: A semiconductor optical amplifier includes a substrate, an active layer located on a ridge of the substrate, a lower cladding layer on the active layer, current blocking layers, an upper cladding layer, a mesa structure which is constituted by a pair of grooves, an electrical insulating film on the surfaces of the upper cladding layer and in the grooves, and a surface electrode which has an electrical contact with the upper cladding layer. In the optical amplifier, the carrier lifetime, ?, in the active layer is ??0.3 ns, and the differential gain, dg/dn, of the active layer?4×10?16 cm2, thereby suppressing overshoot of the optical output waveform.

Abstract: A waveguide-type semiconductor optical device (20) having a pin-type junction formed on a semi-insulating substrate (1). The pin-type junction consists of an n-type cladding layer (2), an i-type absorption layer (4), and a p-type cladding layer (6). The waveguide-type semiconductor optical device includes an impurity concentration of not higher than 1016 cm−3 in the i-type absorption layer.

Abstract: An optical modulator which is capable of lowering the degree of chirping without deteriorating the extinction characteristic. An intermediate layer is interposed between a well layer and an n-side barrier layer and tensile strain is produced in the well layer, whereby a relationship Ew<Em<Eb is established between a band gap Eb (eV) of the barrier layer, the band gap Ew (eV) of the well layer, and the band gap Em (eV) of the intermediate layer. Another type of tensile strain quantum well structure having four kinds of layers may be formed by adding another layer to the above tensile strain quantum well structure having three kinds of layers. The band gap of an additional layer is set between the band gaps of the well layer and the intermediate layer or between the band gaps of the intermediate layer and the barrier layer.

Abstract: An optical modulator which is suitable for use in high-speed optical communications and simultaneously satisfies demands for incident light of higher intensity and lower chirp. An absorption layer having a multi-quantum-well structure includes a well layer having a first bandgap energy, and a barrier layer having a second bandgap energy, the second bandgap energy being greater than the first bandgap energy and no less than 0.946 eV.

Abstract: An optical device having superior frequency characteristics and high optical axis stability. The back surfaces of an optical modulator and a pair of transmission lines are bonded to a pedestal with the transmission lines located on opposite sides of the optical modulator. Conductive bumps are located on the transmission lines and electrode pads on the front surface of the optical modulator. A connection transmission line is bonded to the bumps, so the electrode pads of the optical modulator are connected to the transmission lines via the connection transmission line.

Abstract: The present invention relates to an optical modulator which is suitable for use in high-speed optical communications and simultaneously satisfies demand for incident light of higher intensity and demand for lower chirp. An absorption layer of multi-quantum-well structure is provided. The absorption layer includes a well layer having a first bandgap between the valence band and the conduction band, and a barrier layer having a second bandgap between the valence band and the conduction band, the second bandgap being greater than the first bandgap and being equal to or less than 0.946 eV.

Abstract: It is intended to provide an optical device having superior frequency characteristics and high optical axis stability. The back surfaces of an optical modulator and a pair of transmission lines are bonded to a pedestal in such a manner that the transmission lines are located on both sides of the optical modulator. Conductive bumps are formed on the transmission lines and electrode pads that are formed on the front surface of the optical modulator. A connection transmission line is bonded to the bumps, whereby the electrode pads of the optical modulator are connected to the transmission lines via the connection transmission line.

Abstract: An optical semiconductor module includes a substrate including a first plate member having strip lines for high-frequency signal transmission, located on a surface of the substrate and a second plate member including a feeding line on a surface, the first plate member having a loss angle at high frequencies smaller than that of the second plate member, and the second plate member including a material with a higher heat conductivity than that of the first plate member. The optical semiconductor module includes an integrated semiconductor laser and modulator including a modulator region having surface electrodes on a surface, and a laser region having a surface electrode on a surface, with an optical axis extending along the optical axis of the modulator region. The integrated semiconductor laser and modulator are located on the substrate such that the surface electrodes of the modulator region are bonded to the strip lines and the surface electrode of the laser region is bonded to the feeding line.

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: In an optical semiconductor device including a DFB laser and a light absorption modulator, a semi-insulating semiconductor layer is disposed between a carrier blocking layer and a upper cladding layer, the upper cladding layer having an opposite conductivity type from that of the semiconductor substrate and disposed on a buried waveguide and the carrier blocking layer. The capacitance between the carrier blocking layer and the upper cladding layer is reduced. Therefore, mutual interference between the DFB laser and the light absorption modulator through the carrier blocking layer is reduced.

Abstract: An array type semiconductor laser device includes a foldable submount and a plurality of semiconductor lasers each having uppermost and lowermost layers mounted on the submount. The submount is folded into a polygonal shape having sides with a respective semiconductor laser mounted in the polygon on a corresponding side of the polygon. Therefore, it is easy to mount the semiconductor lasers and a light source can be concentrated on a narrow region.