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: A dielectric sheet is attached to the inner surface of the portable telephone housing. The dielectric sheet extends in the area between the user's head and a whip antenna of the portable telephone. The real part and the imaginary part of the relative dielectric constant of the dielectric sheet is properly selected such that the dielectric sheet can reduce SAR (Specific Absorption Rate) and improve antenna efficiency.

Abstract: A waveguide semiconductor optical device with a mesa ridge structure includes a semi-insulating substrate; and a ridge on the semi-insulating substrate, and including a lower cladding layer, a core layer, and an upper cladding layer sequentially laminated on the semi-insulating substrate, wherein the lower cladding layer includes a first laterally extending from the ridge and having an electrode on a top face, and a second layer with a carrier density lower than that of the first layer and in contact with the core layer.

Abstract: A semiconductor optical integrated circuit includes: a semiconductor substrate; a light reflecting portion and a gain region, formed on the semiconductor substrate; a first optical waveguide connecting between the reflecting portion and the gain region; and a second optical waveguide formed in conjunction with the first optical waveguide and having a larger optical absorptance than that of the first optical waveguide.

Abstract: A semiconductor optical device includes a substrate, an optical waveguide layer on the substrate and having well and barrier layers. The semiconductor optical device also includes an optical absorbing layer on the substrate and adjacent to the optical waveguide layer so that incident light having an incident wavelength &lgr;LD is guided into the optical absorbing layer. Each of the well layers has a wavelength &lgr;g corresponding to the band gap of the well layers and that is larger than the incident wavelength &lgr;LD. Also, the band gap energy between base levels of a conduction band and a valence band of the optical waveguide layer is larger than the energy of the incident light having the incident wavelength &lgr;LD.

Abstract: An optical waveguide ridge has a side with a flat portion extending uniformly from a top of the ridge to a surface of a semiconductor substrate, the flat portion being in contact with an exposed surface of the substrate. A p-type electrode extends from the top of the optical waveguide ridge downward in contact with a dielectric film on the flat portion of the optical waveguide ridge. The p-type electrode further extends over the dielectric film onto the exposed surface of the semiconductor substrate where an end of the electrode is a bonding pad.

Abstract: Input light is split by an input-light splitter into first split light and second split light. A multiplex-interference portion performs multiplex interference of the first split light and the second split light to generate intensity-modulated light having a first wavelength. A phase modulation portion is fed with the intensity-modulated light and continuous wave light having a wavelength equal to a second wavelength, and performs cross-phase modulation of the continuous wave light in accordance with phase modulation of the input light.

Abstract: An electroabsorption semiconductor optical modulator includes a light absorption layer for generating a modulated light beam by absorbing an incident light beam. A well layer in the light absorption layer, accumulates charge carriers generated by the light absorption layer. The charge carriers are guided and released from the well layer upon receipt of an incident excitation light beam having a wavelength corresponding to the bandgap energy of the well layer. The incident light beam is modulated by changes in absorption coefficient in response to an externally applied voltage. The modulator responds to a high-intensity incident light beam at high frequency, free from deterioration of extinction characteristics, and has good transmission characteristics.

Abstract: A plurality of substantially S-shaped optical waveguides are embedded in the semiconductor substrate, and at least two optical waveguide returning parts are interposed between the input and output ends of the bent waveguides, and each of the optical waveguide returning parts includes a multiplexing portion. A reflecting part is formed on a rear end side of the multiplexing portion of each optical waveguide returning part. Thus, the length between the input and output ends of the waveguides can be reduced, suppressing a bending loss, achieving to have a high speed and a small size of the integrated device.

Abstract: A semiconductor optical modulator of an electroabsorption type includes a light absorption layer (12) for generating a modulated light beam by absorbing an incident light beam (L1). A well layer (18) is formed in the light absorption layer, and the carriers generated by the light absorption layer are accumulated in the well layer and guided and released from the well layer upon receipt of an incident excitation light beam (L2) of a wavelength corresponding to the bandgap energy of the well layer. The incident light beam is modulated by use of changes in absorption coefficient under an externally applied voltage based on the Franz-Keldysh effect or the quantum confined Stark effect, thus allowing to respond to high-intensity incident light beam at high frequency, free from deterioration of extinction characteristics, having good transmission characteristics.

Abstract: A semiconductor device has a first semiconductor layer, a second semiconductor layer, and an active layer sandwiched between the first and the second semiconductor layer and emits light from the active layer when a voltage is applied across the first and the second semiconductor layer. The semiconductor device includes an anode on the first semiconductor layer, an insulating film on the anode, and a screen electrode on the insulating film covering at least part of the anode. The second semiconductor layer is grounded and the screen electrode is electrically connected to the grounded second semiconductor layer. The screen electrode screens the anode to prevent flow of a leakage current between the first and second semiconductor layers due to electromagnetic waves.

Abstract: One of the embodiments of the present invention has a purpose to provide a kink-free semiconductor optical device stabilizing a laser oscillation and obtaining a high optical performance. In particular, one of the aspects of the present invention is to provide a semiconductor optical device including a beam waveguide extending in a longitudinal direction between a pair of end surfaces. The beam waveguide includes an active layer of a quantum well structure having at least one well and barrier layers, and a pair of cladding layers sandwiching the active layer. The active layer has a first and second regions in the longitudinal direction, formed so as to have a photon density in the first region greater than that of the second region. The first region has a differential gain greater than that of the second region so that a variation of refractive index across the beam waveguide is reduced.

Abstract: This invention relates to a method of producing a molded transparent covering member. The steps of the method comprise providing a silicon rubber material and a fluorescent substance together to form a material to be molded in a space between an inner surface of an upper mold and an outer surface of a lower mold; sand-blasting at least one of the inner surface of said upper mold and the outer surface of the lower mold; and injecting the material into the space formed between upper mold and the lower mold.

Abstract: The semiconductor optical device according to one of the embodiments includes a substrate, a optical waveguide layer formed on the substrate as a MQW layer having a plurality of well and barrier layers. The semiconductor optical device also includes an optical absorbing layer formed on the substrate and adjacent to the optical waveguide layer so that an incident light having an incident wavelength &lgr;LD through the optical waveguide layer is guided into the optical absorbing layer. Successively formed thereon are a cladding layer and a pair of electrodes. Each of the well layers has a wavelength &lgr;g corresponding to a band gap thereof, that is greater than the incident wavelength &lgr;LD. Also, a band gap energy between base levels of a conduction band and a valence band of the optical waveguide layer is larger than a photon energy of the incident light having the incident wavelength &lgr;LD.

Abstract: A waveguide type semiconductor optical device with a high mesa ridge structure comprising: a semi-insulating substrate; and a ridge formed on the semi-insulating substrate, comprising a lower clad layer, core layer and upper clad layer sequentially laminated on the semi-insulating substrate; wherein the lower clad layer comprises a high-density layer-laterally extending from the ridge and having an electrode placed on a top face thereof, and a low-density layer with a carrier density lower than that of the high-density layer and in contact with the core layer.

Abstract: A modulator and an integrated semiconductor modulator-laser device, in which the capacitance of the modulator is reduced to increase the cut-off frequency, and a manufacturing process for the device. A wire layer connecting a modulator electrode to a pad electrode is interposed between a first embedded layer of InP doped with Fe, extending from the modulator portion, between the insulating layer and the substrate. The wire layer has a capacitance smaller than when the first embedded layer is not beneath the insulating layer. The cut-off frequency of the modulator is increased, improving frequency characteristics. An integrated semiconductor modulator-laser device can include such a modulator.

Abstract: An LED device is provided that has an excellent color rendering property and no toxicity and does not increase production costs more than necessary. A covering member is also provided used for such a device. The LED device comprises a light-emitting element for emitting light in a blue to green region and a fluorescent substance containing a red phosphor for converting the wavelength of the light emitted from the light-emitting element to another wavelength. The red phosphor is CaS activated by Eu or a phosphor expressed by the general formula AEu(1−x)LnxB2O8, wherein A is an element selected from the group consisting of Li, K, Na and Ag; Ln is an element selected from the group consisting of Y, La and Gd; and B is W or Mo; and x is number equal to or larger than 0, but smaller than 1.

Abstract: A semiconductor device has a first semiconductor layer, a second semiconductor layer and an active layer sandwiched between the first and the second semiconductor layer to emit light by the active layer when a voltage is applied across the first and the second semiconductor layer. The semiconductor device includes an anode formed on the first semiconductor layer, an insulating film formed on the anode, and a screen electrode formed on the insulating film so as to cover at least part of the anode. The second semiconductor layer is grounded and the screen electrode is electrically connected to the grounded second semiconductor layer. The screen electrode screens the anode to prevent the flow of leakage current between the first and the second semiconductor layer due to the effect of electromagnetic waves.

Abstract: An integrated semiconductor laser-modulator device less affected by a fluctuating electric field due to modulating signals applied to the modulator has improved frequency characteristics. The integrated semiconductor laser-modulator includes an active layer, a beam waveguide layer having a bulk structure with a bandgap energy larger than that of the active layer but smaller than that of a laser beam absorption layer having a bulk structure, wherein waveguides of the laser and modulator are connected and aligned, and a cladding layer including a diffraction grating is disposed on top of or beneath the waveguides.

Abstract: At least part of the waveguide of a laser, the waveguide including a first cladding layer, an active layer, and a second cladding layer of a second conductivity type, and, for a ridge type laser, a ridge in the second cladding layer, has a width such that light leaks from the side walls of the waveguide. A case encloses the side walls of the waveguide and a fluid having a refractive index is sealed in the case in contact with the side walls of the waveguide. A characteristic of the laser can be adjusted easily. Therefore a laser having a uniform characteristic can be provided at a low cost. This laser is useful as a light source for wavelength multiplex transmission used for optical transmission, of a main line system, such as a submarine cable.