Abstract: A planar lightwave circuit type variable optical attenuator with a small polarization dependent loss is provided. By setting the waveguide birefringence (absolute value) in first and second optical coupler sections equal to or greater than 3.5×10?4, the polarization mode coupling is made equal to or less than ?25 dB, and the effect of the polarization dependence caused by the polarization mode coupling at the cross port of the first and second optical couplers is suppressed. In addition to or independently of this, the arm waveguide length can be designed to be equal to an integer multiple of the optical beat length obtained by dividing a used optical wavelength by the waveguide birefringence.

Abstract: A planar lightwave circuit type variable optical attenuator with a small polarization dependent loss is provided. By setting the waveguide birefringence (absolute value) in first and second optical coupler sections equal to or greater than 3.5×10?4, the polarization mode coupling is made equal to or less than ?25 dB, and the effect of the polarization dependence caused by the polarization mode coupling at the cross port of the first and second optical couplers is suppressed. In addition to or independently of this, the arm waveguide length can be designed to be equal to an integer multiple of the optical beat length obtained by dividing a used optical wavelength by the waveguide birefringence.

Abstract: In the disclosed optical signal processing device, the digital-to-analog conversion of the input optical signals is realized in an optical region, without converting the input optical signals into electric signals for the purpose of signal processing, by splitting input optical signals into plural sets, delaying the split optical signals for mutually different delay amounts while adjusting amplitudes of these optical signals, combining these optical signals, and gating these optical signals on a time axis. It is also possible to realize the processing of the optical signals that are multiplexed on a time axis such as interchanges of time-slots similarly.

Abstract: A planar lightwave circuit is provided. The planar lightwave circuit includes a waveguide and a spotsize converter which is a part of the waveguide, wherein a core is embedded in a cladding in the waveguide, and the spotsize converter is located near an end face of a substrate on which the planar lightwave circuit is formed, the spotsize converter including: a core width fine-tuning part in an end face side of the substrate; and a core width converting part which follows the core width fine-tuning part; wherein core width of the spotsize converter is minimum at an end face of the substrate, a mean taper angle ?1 of the core width fine-tuning part is larger than 0° and smaller than a mean taper angle ?2 of the core width converting part.

Abstract: An interferometer includes a waveguide core, and thin film heaters with widths W1 and W2. The thin film heaters are mounted directly above the waveguide core, and operate as two types of different annealing regions. The annealing, which is carried out by supplying current to the thin film heaters, can alter the quality of the cladding, and change the stress applied on the waveguide core, thereby making it possible to control the polarization dependency. Thus changing the width of the thin film heaters and/or the amount of the supply current thereto enables the permanent control of the effective refractive index (birefringence index) independently in the transverse electric polarization mode and the transverse magnetic polarization mode. This enables the transverse electric polarization mode to be adjusted to a phase difference of &lgr;/2, and the transverse magnetic polarization mode to a phase difference of zero.

Abstract: A silica-based optical waveguide circuit serves to reduce the time required to production while allowing a spot size converting function to work sufficiently. In a silica-based optical waveguide circuit comprising an input/output waveguide core formed to be thicker than an waveguide core and a tapered portion for connecting the input/output waveguide core and the waveguide core, wherein the waveguide circuit further has a core layer at each side of the input/output waveguide core, a thickness T of the core layer at the side of the input/output waveguide core is smaller than the thickness H of the input/output waveguide core.

Abstract: It is an object of the present invention to provide an optical filter which allows parameters to be easily adjusted, which allows birefringence and temperature dependence to be easily compensated for, and which is essentially free from dispersion. The optical filter includes an optical coupler that splits light into two beams, optical couplers connected to outputs of the optical coupler, a first group of two optical waveguide delay lines connected to the coupler, a second group of two optical waveguide delay lines connected to the coupler, an optical coupler that combines lights from the first group of the lines, an optical coupler that combines lights from the second group of the lines, and a multimode interference optical coupler that combines lights from the couplers together.

Abstract: An optical waveguide and an optical waveguide circuit having polarization insensitivity or a required low-level polarization dependence without degradation of the optical characteristics and reliability are disclosed, and a fabricating method of an optical waveguide and an optical waveguide circuit having polarization insensitivity or a required low-level polarization dependence without increasing the fabricating burden and the cost are disclosed. The optical waveguide comprises a planar substrate; a lower cladding which is provided on the planar substrate, where the lower cladding has a ridge; a core, provided on the ridge of the lower cladding, for transmitting light; and an upper cladding provided in a manner such that the core is covered with the upper cladding. The ridge has a shape predetermined so as to decrease polarization dependence of the optical waveguide to a required low level.

Abstract: It is an object of the present invention to provide an optical filter which allows parameters to be easily adjusted, which allows birefringence and temperature dependence to be easily compensated for, and which is essentially free from dispersion. The optical filter includes an optical coupler that splits light into two beams, optical couplers connected to outputs of the optical coupler, a first group of two optical waveguide delay lines connected to the coupler, a second group of two optical waveguide delay lines connected to the coupler, an optical coupler that combines lights from the first group of the lines, an optical coupler that combines lights from the second group of the lines, and a multimode interference optical coupler that combines lights from the couplers together.

Abstract: A silica-based optical waveguide circuit serves to reduce the time required to production while allowing a spot size converting function to work sufficiently. In a silica-based optical waveguide circuit comprising an input/output waveguide core formed to be thicker than an waveguide core and a tapered portion for connecting the input/output waveguide core and the waveguide core, wherein the waveguide circuit further has a core layer at each side of the input/output waveguide core, a thickness T of the core layer at the side of the input/output waveguide core is smaller than the thickness H of the input/output waveguide core.

Abstract: A planar lightwave circuit is provided. The planar lightwave circuit includes a waveguide and a spotsize converter which is a part of the waveguide, wherein a core is embedded in a cladding in the waveguide, and the spotsize converter is located near an end face of a substrate on which the planar lightwave circuit is formed, the spotsize converter including: a core width fine-tuning part in an end face side of the substrate; and a core width converting part which follows the core width fine-tuning part; wherein core width of the spotsize converter is minimum at an end face of the substrate, a mean taper angle &thgr;1 of the core width fine-tuning part is larger than 0° and smaller than a mean taper angle &thgr;2 of the core width converting part.

Abstract: An interferometer includes a waveguide core, and thin film heaters with widths W1 and W2. The thin film heaters are mounted directly above the waveguide core, and operate as two types of different annealing regions. The annealing, which is carried out by supplying current to the thin film heaters, can alter the quality of the cladding, and change the stress applied on the waveguide core, thereby making it possible to control the polarization dependency. Thus changing the width of the thin film heaters and/or the amount of the supply current thereto enables the permanent control of the effective refractive index (birefringence index) independently in the transverse electric polarization mode and the transverse magnetic polarization mode. This enables the transverse electric polarization mode to be adjusted to a phase difference of &lgr;/2, and the transverse magnetic polarization mode to a phase difference of zero.

Abstract: An optical waveguide and an optical waveguide circuit having polarization insensitivity or a required low-level polarization dependence without degradation of the optical characteristics and reliability are disclosed, and a fabricating method of an optical waveguide and an optical waveguide circuit having polarization insensitivity or a required low-level polarization dependence without increasing the fabricating burden and the cost are disclosed. The optical waveguide comprises a planar substrate; a lower cladding which is provided on the planar substrate, where the lower cladding has a ridge; a core, provided on the ridge of the lower cladding, for transmitting light; and an upper cladding provided in a manner such that the core is covered with the upper cladding. The ridge has a shape predetermined so as to decrease polarization dependence of the optical waveguide to a required low level.

Abstract: In the disclosed optical signal processing device, the digital-to-analog conversion of the input optical signals is realized in an optical region, without converting the input optical signals into electric signals for the purpose of signal processing, by splitting input optical signals into plural sets, delaying the split optical signals for mutually different delay amounts while adjusting amplitudes of these optical signals, combining these optical signals, and gating these optical signals on a time axis. It is also possible to realize the processing of the optical signals that are multiplexed on a time axis such as interchanges of time-slots similarly.

Abstract: A silver halide photosensitive material having an improved antistatic property is disclosed, comprising a base support having thereon an electrically conductive layer comprised of fine particles of a crystalline metal oxide selected from the group consisting of ZnO, TiO.sub.2, ZrO.sub.2, SnO.sub.2, Al.sub.2 O.sub.3, In.sub.2 O.sub.3, SiO.sub.2, MgO, BaO and MoO.sub.3 or a composite oxide thereof dispersed in a binder, the light scattering efficiency of said photosensitive material being 50% or less. The electrically conductive layer gives excellent antistatic properties even under low humidity preventing the generation of static charges without damaging photographic properties of the silver halide photosensitive material.

Abstract: An electrically-conductive support for an electrophotographic medium, comprising a support and an electrically-conductive layer provided on the support is disclosed. The electrically-conductive layer comprises a binder and electrically-conductive metal oxide fine particles having an average grain size of 0.5.mu. or less, dispersed in the binder.

Abstract: A magnetic recording medium is disclosed which is comprised of a nonmagnetic support base having a magnetic layer disposed on one surface. A back coating is disposed on the opposite surface of the support base in order to provide the magnetic recording medium with greater durability without increasing the coefficient of friction. The back coating is comprised of a binder having inorganic particles dispersed therein, the inorganic particles including SnO.sub.2 particles having an average size of about 0.01 to about 0.8.mu.. The back coating does not reduce the S/N ratio of the recording medium.

Abstract: A process for producing a developer for electrostatic latent images comprising adding a solution (A) of a high-molecular weight compound having electron-donating functional groups dissolved in an organic solvent (1) which is a good solvent for the high-molecular weight compound to an organic solvent (2) in which the high-molecular weight compound is substantially insoluble, thereby depositing the high-molecular weight compound in a finely divided particle form, wherein an organic resin which is soluble in both of organic solvent (1) and organic solvent (2) is dissolved in at least one of solution (A) and organic solvent (2).

Abstract: An electrophotographic photosensitive layer comprising finely divided photoconductive powders and a resin binder comprising a mixture of an acrylic resin and an epoxy ester resin in a ratio by volume of the acrylic resin to the epoxy ester resin of about 10:90 to 70:30; and an electrophotographic marking method suitable for use on substrates subsequently machined comprising electrophotographically marking machining information on a coating film, forming on a support to be machined, of the electrophotographic photosensitive layer as defined above and hardening the coating film.

Abstract: A method of forming an electrophotographic coating which includes preparing a mixture which comprises finely divided photoconductive material dispersed in an organic resin binder. The resin, which exhibits an acid value of at least 3, or a hydroxyl value of at least 15, is heat-treated for a time and temperature enclosed within the area ABCDEFGH of the temperature-treating diagram shown in the accompanying drawing. Following this treatment, the mixture is dissolved in a volatile solvent for the binder resin, and the dispersion is coated onto a conductive backing to form a substantially uniform layer.