Abstract: The subject to be attained by the disclosed technique is to provide an optical unit less expensive than conventional like optical units and having a wavelength multiplexer and optical waveguides. For achieving the above subject there is provided a wavelength multiplexer wherein a light combining/branching section is constituted by a multi-mode interference type optical waveguide, and an incident-side optical waveguide and a reflection-side optical waveguide are spaced a predetermined distance from each other at their connections to the multi-mode interference type optical waveguide. An optical filter is installed in the multi-mode interference type optical waveguide and a multi-mode interference is set so that a peak in a light intensity distribution is formed in the vicinity of an inlet of each of an exit-side optical waveguide and the reflection-side optical waveguide.

Abstract: An optical switch operating on thermooptic effects has a branching section heater for heating a branching section of a core and a branched core heater for heating a branched core. The heaters are controlled separately so that the branching section and the branched core can be heated to respective temperatures so as to minimize insertion loss of inputted light and to prevent outputting light from a port not intended for light output.

Abstract: Disclosed is an optical communication module comprising: an active optical device includes a first optical waveguide through which light passes; and an optical waveguide device including a second optical waveguide, the second optical waveguide having an input end surface through which the light emitted from an output end of the first optical waveguide is incident to the second optical waveguide, wherein the output end of the first optical waveguide has a first unit vector which represents a direction in which light passing a predetermined first point on the output end proceeds.

Abstract: Substantially sharp corners for optical waveguides in integrated optical devices, photonic crystal devices, or for micro-devices, can be fabricated. Non-sharp corners such as rounded corners, are first formed using lithographic patterning and vertical etching. Next, isotropic etching is used to sharpen the rounded corners. A monitor can be used to determine if the rounded corners have been sufficiently sharpened by the isotropic etching.

Abstract: Disclosed is a microbend fiber optic coupler and a method of forming same. The microbend fiber optic coupler includes two pairs of pigtail ends oriented one beside the other and having a bent fused biconically tapered coupling region interposed therebetween.

Abstract: Optical apparatus and optical switching methods that provide optical high data rate switching at a wavelength or packet level using optical tone addressing. Optical signal routing is a result of optically induced total internal reflection at the intersection of an X-junction waveguide structure. The total internal reflection effect is controlled by a high intensity optical pump beam separate from the optical data signal. Total internal reflection may result from a free-carrier induced change in refractive index, which is a nonlinear effect found in common III-V semiconductors and selected polymers. Optical switching networks may be formed using cascaded pluralities of optical waveguide switches.

Abstract: A process for producing a polymer optical waveguide in which all of one or a plurality of start points and all of one or a plurality of end points of a wave guide are uniformly aligned along a same single straight line. The process comprises the steps of: preparing a mold comprising a concave portion for forming a core; bringing a cladding substrate into close contact with the mold disposing a concave portion toward the cladding substrate; filling the concave portion of the mold with a core-forming curable resin; curing the core-forming curable resin in the concave portion to form a core; and cutting a cladding substrate possessing a core part and a cladding layer thereon along the same single straight line.

Abstract: Disclosed is a thermo-optic (TO) switch that reduces the difficulty in the fabrication process and has an excellent optical crosstalk. In the TO switch, variable optical attenuators utilizing higher-order mode generators are integrated to the both output ports of a conventional 1×2 digital TO switch of Y-branch type waveguide which uses mode evolution effect. Even when the Y-branch angle gets bigger, the inventive TO switch can maintain an excellent crosstalk without raising the switching power. Since a large Y-branch angle can reduce the difficulty in fabrication process, the inventive TO switch will increase the production rate. 1×2 optical switch is an essential device in an optical signal processing system such as optical communications, optical switches and optical sensors.

Abstract: In an optical waveguide Y junction, comprising an input waveguide path, a split portion having one end smoothly connected to an end of said input waveguide path, and a pair of bifurcated ends, and a pair of output waveguide paths each having an end smoothly connected to a corresponding one of said bifurcated ends of said split portion, the split portion defines a modified asymmetric Y-shaped waveguide path which is defined by modifying an original symmetric Y-shaped waveguide path having a substantially constant width by removing an asymmetric wedge-shaped section from a side of the split portion interposed between the output waveguide paths. Thus, simply by changing the inner profile of the split portion, a desired uneven split ratio can be achieved without providing a spread out split portion or requiring any abrupt change in the shape of the waveguide path. This contributes to the reduction in the loss of the signal light.

Abstract: The invention relates to an optical branching device connected to a light output end face of an optical waveguide device or an optical branching device and for branching input light, and has an object to provide the optical branching device in which optical axis alignment is easy and the lowering of yield is suppressed.

Abstract: In a digital optical switch, an input waveguide and two output waveguides form a Y-shaped splitter or switch. Electrodes are positioned on each output waveguide at the junction with the input waveguide. The electrodes extend as narrow strips across the waveguides. The inner edges of the electrodes are curved to form a smooth continuation profile to the signal paths to reduce losses.

Abstract: An active optical device comprises a packaged optical chip, an optical fiber coupled to the chip to receive an optical output from it, and a photodetector located within the package for receiving radiation light responsive to the amplitude of that optical output. The radiation light is produced by destructive interference in a pair of waveguides that merge together at a chosen small angle and sufficiently smoothly for a substantial part of the light (ideally nearly all of it) to propagate through the substrate of the chip close to the output waveguide and preferably in only two directions (corresponding to a first-order diffraction). The optical fiber is coupled to the chip by means of a fiber support (such as a fiber block or a ferrule) made of transparent material, and the photodetector is positioned to receive the radiation light at least partly through the fiber support and at least partly by reflection from the interior of the package.

Abstract: Optical structures useful in splitters, couplers, combiners, and switches are provided. An example optical structure has a Y-branch configuration that includes a linear taper segment and two branching waveguides. A straight section extends between the linear taper segment and the two branching waveguides to reduce losses during splitting/combining operation. The straight section may be used in Y-branch configurations having a blunt section, as well as configurations without a blunt section. Straight sections formed of a single segment and of multiple segments are shown, and the straight sections may be formed of substantially parallel outer walls or fanning-out outer walls. Further, in some embodiments, the branching waveguides form acute angles at the boundaries with the straight segment.

Abstract: Disclosed is an optical power splitter that can minimize the chip size with its manufacturing cost. The optical power splitter has one input optical waveguide and N output optical waveguides and splits an optical signal incident from the input optical waveguide into N optical signals. The optical power splitter includes at least two optical splitters having a structure of a planar lightwave circuit element and arranged apart from one another at predetermined intervals in a single chip, and an alignment waveguide for aligning the input and output optical waveguides of the plurality of optical splitters.

Abstract: A two-dimensional photonic crystal slab apparatus having a waveguiding capability is provided. Noncircular holes are introduced to replace the circular holes in the two-dimensional lattice of the photonic crystal to provide waveguiding capability. Waveguide bends and splitter using noncircular holes with high transmittances are described for symmetry planes of the two dimensional lattice structure.

Abstract: An optical wavelength filter having an optical coupler, for suppressing the generation of a double peak caused by a difference of propagation constants between intrinsic modes of light in an optical coupler. The optical wavelength filter includes first and second optical couplers for exciting multiple modes of light in each wavelength of WDM light and providing a phase difference of p/2 between different modes of multiple modes of light, and a mode converter provided between the first and second optical couplers. The mode converter performs mode conversion between the modes of light belonging to a specific wavelength, whereby the phase difference of each mode of light constituting the light of a specific wavelength, and the phase difference between the modes of light constituting the light of another wavelength, are independently adjusted so as to output light of a specific wavelength and light of another wavelength from separate output ports.

Abstract: This two input two output type optical switch includes four one input two output type optical switches which are arranged to oppose one another, each of these one input two output type optical switches including a Y branch portion in which one optical wavegude is branched into two optical wavegudes. And two refractive index adjustment means are provided in the vicinity of each Y branch portion. Switching over of the optical path is performed by half of the refractive index adjustment means functioning alternately. Moreover, a light output intensity variable attenuation function which attenuates by any desired amount the intensity of the light which is being outputted is implemented, at some input port and/or output port, by operating at least one of the refractive index adjustment means which is not currently being used for switching over of the optical path.

Abstract: There are provided an optical waveguide device in which a plurality of PLC type optical waveguide chips are optically coupled to one another at high accuracy by passive alignment, and a method of manufacturing the device. A plurality of optical waveguide chips are formed by cutting an optical waveguide device comprising an optical waveguide substrate having an optical waveguide of a predetermined pattern formed thereon and guide grooves formed on both sides of the optical waveguide on the optical waveguide substrate in the longitudinal direction thereof, in the direction of traversing the optical waveguide substrate at substantially right angle thereto and passing through an intersection of the optical waveguide.

Abstract: The invention relates to an optical branching circuit connected to a light output end face of an optical waveguide circuit or an optical branching circuit and for branching input light, and has a feature to provide an optical branching circuit with less branching ratio variation. The optical branching circuit is comprised of an input optical waveguide formed on a silica glass substrate and for outputting input light inputted from a light input end face to a light output end face, a tapered optical waveguide disposed to be shifted with respect to the input optical waveguide at the light output end face, and branching optical waveguides connected to a light output end face of the tapered optical waveguide at a predetermined branching angle.

Abstract: A dispersion compensating module, mode converter, coupler and dispersion compensated optical fiber therein. The dispersion compensating fiber has a plurality of core segments, the refractive index profile being selected to exhibit properties such that an LP02 mode at 1550 nm may be propagated a distance (generally 0.5-3.0 km), upon conversion to LP02, to compensate for dispersion of a length of transmission waveguide preferably greater than 25 km propagating in an LP01 mode. In another embodiment, the dispersion compensating module has a mode converter having a reflective fiber grating for converting a first to a second mode interconnected to a dispersion compensated fiber propagating in the second mode. The mode converter has a coupler adapted to operatively couple light propagating in a first mode from a first fiber into a second, and a reflective fiber grating operatively coupled to the second fiber; the grating being capable of converting light from the first into the second mode.

Abstract: A device for generating an electrical signal that is a function of the optical power in an optical fiber. The device is comprised of a support substrate, a fused, bi-conically-tapered splitter-coupler, and a glass bead securing an optical fiber extending from the splitter-coupler to the substrate. An opening in the glass bead forms a gap in the optical fiber. A light-sensitive device is disposed in the opening to receive light traveling through the optical fiber from the splitter-coupler.

Abstract: An optical interconnection apparatus including waveguide arrays such as waveguide lenses, waveguide gratings and star couplers, has improved efficiency realized by using a periodic array including in each period a combination of two radial waveguides. The array is formed with angular period &agr; between an input circle and an output circle and it includes an input section, connected to the input circle, and an output section connected to the output circle. The input section includes a single waveguide in each period and it is efficiently coupled with minimal loss to the output section, whose waveguides are approximately arranged with period &agr;/2 in the final region close to the output circle.

Abstract: An apparatus and method for photonically sampling an analog signal and encoding the photonically sampled signal. The two interferometer arms of a Mach-Zehnder interferometer section are directly coupled to the dual input ports of a directional coupler switch section. Optical pulses transmitted through the interferometer arms are phase shifted in proportion to an analog signal applied at the electrical input port of the Mach-Zehnder interferometer section. The phase-shifted pulses in each interferometer arm are coupled in the directional coupler switch section and are directed to the dual output ports of the directional switch section based upon the binary code applied to the electrical input port of the directional coupler switch section. The directional switch section has an optical length designed to provide a net phase shift of 3&pgr;/4.

Abstract: The present invention relates to a semiconductor optical tap comprising: a multimode interferometer (MMI) (6); an input waveguide (1) coupled to the MMI; a first output waveguide (2) coupled to the MMI; and a second output waveguide (3) coupled to the MMI. The first and second output waveguides (2,3) overlap (d) such that unequal portions of light are coupled from the MMI into the first and second output waveguides (2,3). The input waveguide (1) and the first and second output waveguides (2,3) may have a rib structure. They may also be adiabatically tapered waveguides. The first and second output waveguides (2,3) may have different starting widths.

Abstract: A photonic bandgap device has a lattice structure, with a waveguide formed by a mesh of defects in the lattice, the defects being located discontinuously, but sufficiently close to each other to provide coupling between overlapping evanescent defect modes. By changing shape and configuration of the mesh and varying the types of defects, it is easier to control the width and position of the transmission band, in wavelength terms, compared to a waveguide formed only from a planar defect, i.e. a single line of defects. Multiplexers, demultiplexers, filters, switches, combiners, and splitters may be created. Many devices and different types of devices can be integrated onto the same crystal lattice, with far greater compactness than planar waveguide technology. The mesh can have a periodic structure of lines of defects, or periodic spacing between defects to reduce loss.

Abstract: The present invention relates to a method and to apparatus for installing optical fibres in duct systems or like tubular runways, and then preferably for installing optical fibres in duct systems arranged in dwelling rooms in apartment blocks. By using a subpressure that acts from a centrally located suction device connected to the duct system, it is possible to draw one or more optical fibres (19), possibly simultaneously, by suction through a duct (13) in the duct system and lead said fibre or fibres to a centrally arranged collecting point common to said fibres. Handling of the optical fibre and feeding of the fibre into a respective duct is facilitated by placing the suction device centrally in the duct system and by placing a drum (20) on which the optical fibre is coiled at the mouth (14) of the duct, therewith enabling the fibre to be installed by a single workman more quickly than would otherwise be the case.

Abstract: A method is presented for controlling continuous propagation of input light through an optical device having an optical functional element of a controllably adjustable operation to affect light passing therethrough. The input light energy is distributed in a predetermined manner between first and second spatially separated paths, wherein the optical functional element is accommodated in the first path. The first and second paths are recombined downstream of the optical functional element with respect to a direction of light propagation through the device, to produce a light output of the optical device. This allows for directing substailly the entire energy of the input light through the second path, during adjustment of the operation of the functional optical element, and redirecting at least a predetermined portion of the input light to the first path to pass through the functional element, upon completion of the adjustment.

Abstract: An optical power splitter is disclosed that includes a semiconductor substrate, a core layered on the semiconductor substrate, functioning as a transmission medium for optical signals composed of multi channels according to a wavelength. The core includes an input waveguide for receiving the optical signals, and a plurality of output waveguides for outputting part of the optical signals whose powers are split. A cladding encompasses the core. At least one tapered waveguides, which connect a part of internal sides of the output waveguides have widths that gradually decrease along with a longitudinal direction thereof starting from one end of the output waveguide.

Abstract: An optical modulator has optical channels formed in a waveguide substrate in which two of the waveguide channel branches have reverse polarity relative to each other. In addition, the optical modulator has at least one of the following: 1) an electronic signal electrode and an electronic ground electrode are placed in proximity with opposite faces of the waveguide substrate, 2) a portion of said waveguide substrate is removed to afford a reduced electronic signal refractive index, and 3) the waveguide substrate has a fixing substrate attached to it with the refractive index of the fixing substrate lower than said refractive index of the waveguide substrate.

Abstract: An optical power splitter is provided that can stably operate even when there is a mode mismatch between an input optical signal and the optical power splitter. The optical power splitter of the present invention includes a semiconductor substrate, an optical waveguide stacked on the semiconductor substrate, and a clad surrounding the optical waveguide.

Abstract: The invention relates to an integrated waveguide optical tap coupler, which includes an input waveguide, a tapered section, and a pair of output waveguides. The upper edges of the tapered section and one of the output waveguides defines an arc of a circle with a first radius, while the lower edges of the tapered section and the other output waveguide defines an arc of a circle with a second radius. The proximate ends of the two output waveguides are separated by a truncated wedge tip defining a distance S. With this arrangement excess loss is reduced by ensuring the wavefront is continuously tilted and the branching angles are very small.

Abstract: An optical semiconductor device includes an optical modulator and an optical detector formed integrally on a common substrate to form an optical integrated circuit, wherein an optical beam spot conversion part is provided also integrally on the common substrate so as to connect an output end of the optical modulator and an input end of the optical detector.

Abstract: Disclosed is a thermo-optic tunable attenuator, which comprises a single mode channel optical waveguide, an optical waveguide of a Mach-Zehnder interferometer structure coupled with the single mode channel optical waveguide, the optical waveguide including two symmetric Y-branches, and two metal heating wires for applying power to one side of each of the two symmetric Y-branches, wherein the two metal heating wires are in a facing relationship with each other, wherein a refractive index of the optical waveguide is changed in response to a power applied to any one of the two metal heating wires.

Abstract: The present invention makes light input/output portions being a coupling portion with an optical fiber and a Y-branch using a rib waveguide, and a bending portion using a channel waveguide, wherein the rib waveguide and the channel waveguide is connected by a tapered waveguide. So that the present invention can improve the crosstalk, loss and operating voltage characteristics.

Abstract: A broadband optical switch with high process tolerance designed and fabricated using Planar Lightwave Circuits (PLC) technology. A 2×2 configuration of the switch is based on a Mach-Zehnder interferometer (MZI) configuration that includes two 3 dB adiabatic couplers and two identical arms. Each adiabatic coupler is characterized by two straight branches having different widths, separated over a coupling length by a changing spacing therebetween and blending in a symmetric intersection area, which connect to two symmetric branches. The two adiabatic couplers are connected by the two arms with their symmetric branches facing each other along an optical propagation axis. Switch control is realized by changing an optical property of one or both of the MZI arms. Implementation in silica-on-silicon PLCs provides switches with an exceptional broadband range (1.2-1.7 &mgr;m), very high extinction ratios (>34 dB), low fabrication sensitivity and polarization independent operation.

Abstract: A broadband partial reflector is located downstream from an optical combiner device. The partial reflector reflects a portion of the combined light back through the combiner device and back into the respective optical pump sources. There are no fiber gratings or other filters between the sources and the combiner device. Consequently, the sources are locked and/or stabilized according to the acceptance bandpass characteristics of the input ports of the combiner device. Since no gratings or other filters need to be located between the sources and the combiner device, the problem of insertion power loss due to spectral mismatch at the input ports can be avoided. In other words, self-aligned wavelength feedback stabilization is accomplished by reflecting a portion of the combined light signal back through the input ports of the combiner device.

Abstract: A tap coupler device for an optical array is formed either in a waveguide structure or in a V block in which a fiber array may be mounted. The tap coupler device may include a substrate with main and tap waveguides formed therein, and waveguide tap couplers formed in the substrate for diverting a portion of the optical signal from the main waveguides to corresponding tap waveguides. Another variation includes a substrate including waveguides, with the surface of the substrate where the waveguides end inclined to reflect a portion of the signals in the waveguides toward the top surface of the substrate. Yet another variation includes an input V block having input fibers. The surface of the V block where the input fibers terminate is inclined to reflect a portion of light signals from the input fibers toward the top surface of the V block.

Abstract: Disclosed is a microbend fiber optic coupler and a method of forming same. The microbend fiber optic coupler includes two pairs of pigtail ends oriented one beside the other and having a bent fused biconically tapered coupling region interposed therebetween.

Abstract: A rib waveguide structure comprising a layer (4) of light conductive material defined between two planar faces with a rib (9) formed on one of the faces and an optical component e.g. a tapered waveguide (6) optically coupled to the other face. An inverted rib waveguide comprising a light conductive layer (11) and a rib (10) that projects from the light conductive layer (11) into a substrate (4,8) is also described as well as other optical devices comprising a light conductive layer separated from a substrate by a non-planar layer (3) of light confining material and optical devices comprising two or more layers (2, 3; 18, 19, 20) of light confining material buried within a rib with a light conducting component (10; 17; 22) at least a part of which is formed between planes defined by the two layers of light confining material. A method of forming such devices is also described.

Abstract: A Y-branch waveguide includes a single merging side waveguide, two branching waveguides, and a junction area waveguide provided between the merging side waveguide and the branching waveguides and formed in a tapered shape being thicker at the branching than at the merging side. The junction area waveguide and the branching waveguides are connected by two straight waveguides parallel to each other. The straight waveguides extend in the same direction as the direction of propagation of light inside the junction area waveguide, when light is injected from the merging side waveguide.

Abstract: An electro-optic modulator and associated method are provided. The electro-optic modulator includes an optical waveguide comprised of two pairs of coplanar modulation strips, the strips being driven by a controller circuit which applies voltages of equal amplitude and opposite polarity to the strips of each pair. The voltage applied to the first pair of strips may differ from the voltage applied to the second pair of strips, so that a chirp factor may be adjusted if desired. The modulator and associated method exhibit reduced drive voltage requirements.

Abstract: A miniature dense wavelength division multiplexer (DWDM) is disclosed. A plurality of multi-window wavelength multiplexers (MWDM) are cascaded and optically coupled to form a tree, and each of the MWMDMs forming the tree comprises a microbend coupler. The forming of the MWDM tree is characterized by the absence of the bending of optical fibers external to the microbend couplers. A finished DWDM assembly measures less than 50 mm in width.

Abstract: A wavelength demultiplexer is provided whose overall length in a first propagation direction is short, whose production efficiency is high, and whose emission loss is smaller than that of conventional configurations. At the first end face V1, the first boundary line F1 is closer to the second edge H2 than the first edge H1 by the distance “b” (b>0). At the first end face V1, the second boundary line F2 is closer to the first edge H1 than the second edge H2 by the distance “b”. At the third end face V3, the fourth boundary line F4 is closer to the fourth edge H4 than the third edge H3 by the distance “a” (a>0). At the fourth end face V4, the sixth boundary line F6 is closer to the third edge H3 than the fourth edge H4 by the distance “a”.

Abstract: An optical signal transmission system equipped with a magneto-optical modulator is provided. The magneto-optical modulator works to modulate an optical beam emitted from a light source and consists of a polarizer, a magneto-optical element, an analyzer, a dc field generator, a high-frequency field generator, and an impedance adjuster. The dc field generator works to apply a dc bias field to the magneto-optical element. The high-frequency generator is responsive to the high-frequency signal from said high-frequency signal generator to apply a high-frequency field to the magneto-optical element. The impedance adjuster works to adjust impedance of the high-frequency field generator for establishing effective transmission of the high-frequency signal to the high-frequency field generator, thereby increasing a modulation range up to frequencies higher than an upper limit of typical magneto-optical modulators.

Abstract: A Terahertz Optical Asymmetric Demultiplexer (TOAD) having preferably two non-linear elements (NLES) in which the extinction ratio is enhanced by saturating both NLEs when closing a switching window. A data signal input on one port of the TOAD is split onto two optical paths, each including one NLE. The optical paths converge at an output port. To start a switching window, a first control signal is input on an optical path that includes only one of the two NLEs. To close a switching window, one or more control signals are input such that both NLEs receive a control signal at a predetermined time after the first control signal is received by one of the NLEs. Only data signals passing through the first NLE during the switching window are output on the output port. Since both NLEs receive a second control signal at the same time, they decay together and thus avoid creation of unintended switching windows.

Abstract: An optical waveguide has a wavelength division multiplexing (WDM) filter, a first core, a second core and a cladding portion. A reception-light signal having a 1.5 &mgr;m wavelength band transmits through the second core and the WDM filter, and the reception-light signal transmits through an optical fiber and is detected by a photodiode. In contrast, a transmission-light signal having a 1.3 &mgr;m wavelength band transmits through the first core, and a major portion of the transmission-light signal is reflected to the second core by the WDM filter and is output to an outside. The remaining portion of the transmission-light signal undesirably transmits through the WDM filter. Also, stray light derived from the transmission-light signal transmits through the cladding portion of the optical waveguide and the WDM filter.

Abstract: In a digital optical switch, an input waveguide and two output waveguides form a Y-shaped splitter or switch. Electrodes are positioned on each output waveguide at the junction with the input waveguide. The electrodes extend as narrow strips across the waveguides. The inner edges of the electrodes are curved to form a smooth continuation profile to the signal paths to reduce losses.

Abstract: An optical device which utilizes a photothermal optical effect to achieve switching or attenuation includes a waveguide defined by a waveguide core and a surrounding cladding, wherein the polymer waveguide core includes a region consisting of a photothermally responsive material having an absorption coefficient at a switch wavelength or attenuation wavelength that is higher than an absorption coefficient at a signal wavelength. Switching devices include an optical splitter circuit having a branch that includes the photothermally responsive material, and either a multiplexer for introducing light at the switch wavelength into the optical circuit or a light source focused at the photothermally responsive material. Attenuating devices include a Mach-Zehnder type interferometer having a branch that includes the photothermally responsive material and either a multiplexer for introducing light at the attenuation wavelength into the optical circuit or a light source focused at the photothermally responsive material.

Abstract: Based on the two-mode interference principle and the free-carrier plasma dispersion effect, a high carrier injection optical waveguide includes: a pair of optical waveguide elements, one functioning as an optical waveguide input and the other functioning as an optical waveguide output; a two-mode interference (TMI) region, made of semiconductor material, between the optical waveguide input and the optical waveguide output; first and second carrier injection regions; and a lateral carrier collection region, the lateral carrier collection region and the first carrier injection region being positioned on opposite sides of the TMI region with the second carrier injection region being positioned between the lateral carrier collection region and the first carrier injection region. In one implementation, the input and output waveguides are each formed as a Y-branch of two single-mode rib waveguides.

Abstract: The present invention relates a method for manufacturing an optical coupler/splitter. A Y-shaped waveguide core is formed by focusing a laser beam into a cladding layer that is formed from a glass material. At least one portion of this Y-shaped waveguide core other than the input port and the output ports is treated as a refractive index adjustment area. After the portions of the Y-shaped waveguide core other than the refractive index adjustment area have been formed by focusing a laser beam, signal light is inputted into the input port of the Y-shaped waveguide core and the signal light outputted from the output ports of the Y-shaped waveguide core are monitored. The refractive index of the refractive index adjustment area is determined based on the result of the monitoring and is adjusted by focusing a laser beam repeatedly.