Abstract: A semiconductor light-receiving element includes: a light-receiving portion that is provided on a semi-insulating substrate and has a mesa shape in which semiconductor layers are laminated; a lamination structure of insulating films that is provided on a part of a side face of the light-receiving portion and has a structure in which a first insulating film comprised of a silicon nitride film, a second insulating film comprised of a silicon oxynitride film and a third insulating film comprised of a silicon nitride film are laminated in contact with each other; and a resin film that is provided adjacent to the light-receiving portion, the resin film being sandwiched in or between any of the first insulating film, the second insulating film and the third insulating film.

Abstract: Besides normal pixels, a plurality detection pixels are arranged in an imaging surface of an FPD. In preliminary imaging, X-rays are emitted to an imaged body portion of a patient. The detection pixels receive the X-rays passed through the body portion, and output AEC detection signals. If an integral value of the AEC detection signals has reached a threshold value, X-ray emission is stopped and the preliminary imaging is completed. A main exposure condition determination unit determines a main irradiation time, being an irradiation time with the X-rays during the main imaging, based on an irradiation time with the X-rays during the preliminary imaging and the integral value of the AEC detection signals. The main imaging is performed using the main irradiation time. The normal pixels continue a charge accumulation operation over the preliminary imaging and the main imaging to produce an X-ray image for use in diagnosis.

Abstract: An electro-optic device, comprising an insulating layer and a layer of light-carrying material adjacent the insulating layer. The layer of light-carrying material, such as silicon, comprises a first doped region of a first type and a second doped region of a second, different type abutting the first doped region to form a pn junction. The first doped region has a first thickness at the junction, and the second doped region has a second thickness at the junction, the first thickness being greater than the second thickness, defining a waveguide rib in the first doped region for propagating optical signals. Since the position of the junction coincides with the sidewall of the waveguide rib a self-aligned process can be used in order to simplify the fabrication process and increase yield.

Abstract: To provide an X-ray waveguide which: shows a small propagation loss of an X-ray; has a waveguide mode with its phase controlled; does not deteriorate owing to oxidation; and can be easily produced, an X-ray waveguide, including: a core for guiding an X-ray in such a wavelength band that a real part of the refractive index of a material is 1 or less; and a cladding for confining the X-ray in the core, in which: the core has a one-dimensional periodic structure containing multiple materials having different real parts of the refractive index; the multiple materials include one of an organic material, a gas, and a vacuum, and an inorganic material; and the core and the cladding are formed so that the critical angle for total reflection at an interface between the core and the cladding is larger than a Bragg angle resulting from a periodicity of the one-dimensional periodic structure, is realized.

Abstract: An apparatus includes a channel waveguide, a ridge waveguide including a ridge and having a bottom surface, a coupler between the channel waveguide and the ridge waveguide, the coupler including an opening configured to transmit light from the channel waveguide to the ridge waveguide, wherein the opening has a first segment having a first width and a second segment having a second width different from the first width, and a protrusion extending from the ridge beyond the plane of the bottom surface.

Abstract: A method of making a grating in a waveguide includes forming a waveguide material over a substrate, the waveguide material having a thickness less than or equal to about 100 nanometers (nm). The method further includes forming a photoresist over the waveguide material and patterning the photoresist. The method further includes forming a first set of openings in the waveguide material through the patterned substrate and filling the first set of openings with a metal material.

Abstract: A method and system for multi-mode integrated receivers are disclosed and may include receiving an optical signal from an optical fiber coupled to a chip comprising a photonic circuit. The photonic circuit may comprise an optical coupler, one or more multi-mode optical waveguides, and a detector. The received optical signal may be coupled to a plurality of optical modes in the one or more multi-mode optical waveguides, which are communicated to a detector to generate an electrical signal from the communicated modes. The optical coupler may comprise a grating coupler. The chip may comprise a CMOS chip, and the optical fiber may comprise a single-mode or a multi-mode fiber. The detector may comprise a germanium or silicon-germanium photodiode, and/or a waveguide detector. The optical fiber may be coupled to a top surface of the chip and the multi-mode optical waveguides may comprise rib waveguides.

Abstract: Lightguides, devices incorporating lightguides, processes for making lightguides, and tools used to make lightguides are described. A lightguide includes light extractors arranged in a plurality of regions on a surface of the lightguide. The orientation of light extractors in each region is arranged to enhance uniformity and brightness across a surface of the lightguide and to provide enhanced defect hiding. The efficiency of the light extractors is controlled by the angle of a given light extractor face with respect to a light source illuminating the light guide.

Abstract: A ridge waveguide structure includes a substrate having a top surface; a ridge structure protruding from the top surface; and a waveguide formed in the ridge structure and a shape of the waveguide is corresponding to a shape of the ridge structure; the ridge structure includes a Y-shaped input section and a Y-shaped output section, the Y-shaped input section includes a total input section, a first branch and a second branch, the first branch and the second branch are diverged from the total input section and converged into the Y-shaped output section. The relation also relates to an electro-optic modulator.

Abstract: An optical waveguide device includes a wiring substrate, an optical waveguide bonded on the wiring substrate and having a light path conversion inclined surface on both ends, and a light path conversion mirror formed to contact the light path conversion inclined surface of the optical waveguide and formed of a light reflective resin layer or a metal paste layer. In case the light reflective resin layer is used as the light path conversion mirror, the light reflective resin layer may be formed partially only on the side of the light path conversion inclined surface, or may be formed on the whole of the wiring substrate to coat the optical waveguide.

Abstract: The present invention provides a planar waveguide. In one embodiment, the planar waveguide includes first and third layers formed above a substrate and adjacent each other. The first and third layers are formed of a first material having a first index of refraction. The planar waveguide also includes a second layer formed between the first and third layers of a second material having a second index of refraction that is larger than the first index of refraction. The planar waveguide further includes a plurality of organo-functional siloxane based resin or polymer waveguides formed in the second layer. Each organo-functional siloxane based resin or polymer waveguide has an input on one edge of the second layer and an output on one edge of the second layer so that the input and output are on different line-of-sight paths.

Abstract: A surface plasmon optical waveguide includes a lower cladding, a metal thin layer on the lower cladding, low-k dielectric layers spaced apart from each other on one surface of the metal thin layer, and an upper cladding covering the low-k dielectric layers and the metal thin layer uncovered between the low-k dielectric layers. A refractive index of the low-k dielectric layers is less than a refractive index of the lower and upper claddings.

Abstract: A method for fabricating an optical waveguide includes setting, on a lower cladding of an optical waveguide, a light-reflecting feature and at least one waveguide core distinct from the reflecting feature. An upper cladding is applied that embeds both the light-reflecting feature and the waveguide core.

Abstract: In one aspect of the invention, roughly stated, Applicants have discovered that a compensation material within slot elongated in a direction parallel to a segment of waveguide in an arrayed waveguide grating apparatus can compensate for both first and second order change in refractive index of the base waveguide material over temperature. Unlike the transverse slots of conventional linear athermalization techniques, the elongated slot generally parallel to the base material defines a composite waveguide section having a second order effective index of refraction temperature dependency which can be utilized to accurately minimize the temperature dependence of the overall optical path length to both the first and second order. The techniques described herein are also generalizeable to neutralization of the optical path length temperature dependence to any order.

Abstract: The present invention addresses the simultaneous detection and quantitative measurement of multiple biomolecules, e.g., pathogen biomarkers through either a sandwich assay approach or a lipid insertion approach. The invention can further employ a multichannel, structure with multi-sensor elements per channel.

Abstract: A patterned nonreciprocal optical resonator structure is provided that includes a resonator structure that receives an optical signal. A top cladding layer is deposited on a selective portion of the resonator structure. The top cladding layer is patterned so as to expose the core of the resonator structure defined by the selective portion. A magneto-optically active layer includes a magneto-optical medium being deposited on the exposed core of the resonator structure so as to generate optical non-reciprocity.

Abstract: The present invention relates to a multimode optical fiber provided with a region where a refractive index in a peripheral region of a core has deviation from an ideal shape of an ?-power refractive-index profile and where an absolute value of an amount of the deviation is not less than 0.005%, so as to generate radiation modes, and a refractive index of a cladding is higher than that of the deviation region.

Abstract: A process for preparing a subassembly, the process comprising: (a) defining the location of one or more grooves for receiving optical conduits on the top planar surface of a wafer or panel, the grooves corresponding to multiple interposers on the wafer or panel; and (b) etching the grooves into the wafer or panel, each groove having sidewalls and first and second terminal ends and a first facet at each terminal end perpendicular to the side walls, each first facet having a first angle relative to the top planar surface, each groove being shared by a pair of transmitting and receiving interposers on the wafer or panel prior to being diced such that the first and second terminal ends of each groove correspond to transmitting and receiving interposers, respectively.

Abstract: A semiconductor optical device includes a first clad layer, a second clad layer and an optical waveguide layer sandwiched between the first clad layer and the second clad layer, wherein the optical waveguide layer includes a first semiconductor layer, a second semiconductor layer disposed on the first semiconductor layer and extending in one direction, and a third semiconductor layer covering a top surface of the second semiconductor layer, and wherein the first semiconductor layer includes an n-type region disposed on one side of the second semiconductor layer, a p-type region disposed on the other side of the second semiconductor layer, and an i-type region disposed between the n-type region and the p-type region, and wherein the second semiconductor layer has a band gap narrower than band gaps of the first semiconductor layer and the third semiconductor layer.

Abstract: Novel integrated electro-optic structures such as modulators and switches and methods for fabrication of the same are disclosed in a variety of embodiments. In an illustrative embodiment, a device includes a substrate with a waveguide and an optical resonator comprising polycrystalline silicon positioned on the substrate. First and second doped semiconducting regions also comprise polycrystalline silicon and are positioned proximate to the first optical resonator. The first optical resonator is communicatively coupled to the waveguide.

Abstract: A monolithically integrated optical device. The device has a gallium and nitrogen containing substrate member having a surface region configured on either a non-polar or semi-polar orientation. The device also has a first waveguide structure configured in a first direction overlying a first portion of the surface region. The device also has a second waveguide structure integrally configured with the first waveguide structure. The first direction is substantially perpendicular to the second direction.

Abstract: Provided are a waveguide with which strain and defect caused by a manufacturing process or the like or caused in a semiconductor in an initial stage or during operation are suppressed so that improvement and stabilization of characteristics are expected, and a method of manufacturing the waveguide. A waveguide includes a first conductor layer and a second conductor layer that are composed of a negative dielectric constant medium having a negative real part of dielectric constant with respect to an electromagnetic wave in a waveguide mode, and a core layer that is in contact with and placed between the first conductor layer and the second conductor layer, and includes a semiconductor portion. The core layer including the semiconductor portion has a particular depressed and projected structure extending in an in-plane direction.

Abstract: The present invention provides a waveguide coupler configured to optically couple a strip waveguide to a first slot photonic crystal waveguide, wherein the slot photonic crystal waveguide has a lattice constant, an air hole diameter, a slot width and a first line defect waveguide width. The waveguide coupler includes a group reflective index taper having a second slot photonic crystal waveguide disposed between and aligned with the first slot photonic crystal waveguide and the strip waveguide. The second slot photonic crystal waveguide has a length, the lattice constant, the air hole diameter, the slot width, and a second line defect waveguide width that is substantially equal to the first line defect waveguide width adjacent to the first slot photonic crystal waveguide and decreases along the length of the second photonic crystal waveguide.

Abstract: According to aspects of embodiments, an optical device includes a first coupler configured to split an optical signal; a second coupler configured to cause optical signals to interfere with each other, a first waveguide configured to couple the first coupler to the second coupler, the first waveguide includes a first phase shifter region having a section narrower in width than an end of the first phase shifter region, the second waveguide includes a second phase shifter region having a section wider in width than an end of the second phase shifter region.

Abstract: An optical waveguide contains a lower cladding layer, a patterned core layer, an upper cladding layer and an upper low elasticity layer, which are laminated in this order, in which a film formed by curing a resin composition for forming the upper low elasticity layer has a tensile elastic modulus of from 1 to 2,000 MPa at 25° C., and a cured film having a thickness of 110 ?m formed by curing a resin composition for forming the upper cladding layer has a total light transmittance of 90% or more. An optical waveguide that has good flexural resistance and good optical characteristics can be provided.

Abstract: Embodiments of the invention relate to an electro-optic device comprising a first region of silicon semiconductor material and a second region of III-V semiconductor material. A waveguide of the optical device is formed in part by a ridge in the second region. An optical mode of the waveguide is laterally confined by the ridge of the second region and vertically confined by a vertical boundary included in the first region. The ridge structure further serves as a current confinement structure over the active region of the electro-optic device, eliminating the need for implantation or other structures that are known to present reliability problems during manufacturing. The lack of “voids” and implants in electro-optic devices according to embodiments of the invention leads to better device reliability, process repeatability and improved mechanical strength.

Abstract: An optical device and an optical transmitter are provided. The optical device includes a substrate, a first optical waveguide that may be formed in the substrate and may have a bending portion, and a second optical waveguide that intersects with the bending portion of the first optical waveguide, wherein a groove may be formed outside the bending portion of the first optical waveguide in the substrate.

Abstract: Devices, systems and techniques for directly coupling an optical slot waveguide to another optical waveguide without a taper waveguide region between the two optical waveguides.

Abstract: Various exemplary embodiments relate to an optical isolator in an integrated optical circuit including: a first optical modulator configured to provide a first periodic phase modulation on an input optical signal; a second optical modulator configured to provide a second periodic phase modulation on the modulated optical signal; and an optical waveguide having a length L connecting the first optical modulator to the second optical modulator; wherein the phase difference between the first and second periodic phase modulation is ?/2, and wherein the length L of the optical waveguide causes a phase delay of ?/2 on an optical signal traversing the optical waveguide.

Abstract: An aspect of the present invention is directed to a method for forming a mirror-reflecting film on a waveguide in an optical wiring board, characterized in that a multilayer film, in which a base, a metal layer and an adhesive layer are layered in this order, is used, and the metal layer is transferred and bonded to an inclined face for mirror-reflecting film formation provided on the waveguide, with the adhesive layer of the multilayer film intervening. The present invention provides a method which, when forming a mirror-reflecting film on a waveguide in an optical wiring board, enables inexpensive and easy formation of the mirror-reflecting film, using the smallest quantity of metal possible and employing comparatively simple facilities and techniques.

Abstract: An optical printed circuit board, including at least one optical waveguide for carrying optical signals on the optical printed circuit board; and a trench formed adjacent the at least one optical waveguide, wherein the trench contains a light absorptive material to absorb light that strays from the at least one waveguide.

Abstract: An optical signal transmitting device includes a substrate, light emitting modules, an optical coupling element, an optical fiber module, and a pressing pole. The substrate has a first loading surface and a second loading surface. The optical coupling element is positioned on the first loading surface and includes a first cladding portion and coupling lenses. Each coupling lens has a first sloped surface and a second sloped surface. The light emitting modules are positioned on the second loading surface and spatially correspond to the respective first sloped surfaces. The optical fiber module is positioned on the first loading surface and includes a second cladding portion and fiber cores. Each fiber core has a bare end. The pressing pole presses each bare end to the corresponding second sloped surface. The refractive indexes of the substrate, the coupling lenses, the fiber cores and the air are n1, n2, n3, n0, wherein n3>n2>>n1>n0.

Abstract: A high quality factor optical resonator structure includes a substrate, a center disc formed on the substrate, and a plurality of concentric grating rings surrounding the center disc. The concentric rings are spaced apart from the center disc and from one another by regions of lower index of refraction material with respect thereto, and wherein spacing between the grating rings and the center disc is non-periodic such that a magnitude of a displacement distance of a given grating ring with respect to a ?/4 Bragg reflector geometry is largest for a first of the grating rings immediately adjacent the center disk and decreases in a radially outward direction.

Abstract: An optical modulation device 1 includes a supporting body 2 including a pair of grooves 2b, 2c and a protrusion 2d between the grooves, a ridge par 6 including a channel type optical waveguide capable of multi mode propagation, a first side plate part 3A formed in a first side of the ridge part 6, a second side plate part 3B formed in a second side of the ridge part, a first adhesive layer 4A adhering the first side plate part 3A and the supporting body 2, a second adhesive layer 4B adhering the second side plate part 3B and the supporting body 2, and a third adhesive layer 4C adhering the ridge part 6 and the protrusion 2d. The device 1 further includes a first electrode 7A provided on a side face 6b of the ridge part on the first groove side, and a side face 3b and an upper face 3c of the first side plate part, and a second electrode 7B provided on a side face 6c of the ridge part 6 in the second groove side, the second groove 2c and a side face 3b and an upper face 3c of the second side plate part 3B.

Abstract: Technologies are generally described for an optical waveguide, methods and systems effective to form an optical waveguide, and an optical system including an optical waveguide. In some examples, the optical waveguide may include a silicon oxynitride region in a wall of the silicon substrate. The silicon oxynitride region may define an inner region of the optical waveguide. The wall may define a via. The optical waveguide may include a silicon oxide region in the substrate. The silicon oxide region may define an outer region of the optical waveguide adjacent to the inner region.

Abstract: A method for transferring a thin layer from a lithium-based first substrate includes proton exchange between the first substrate and a first electrolyte, which is an acid, through a free face of the first substrate so as to replace lithium ions of the first substrate by protons, in a proportion between 10% and 80%, over a first depth e1. A reverse proton exchange between the first substrate and a second electrolyte, through the free face is carried out so as to replace substantially all the protons with lithium ions over a second depth e2 smaller than the first depth e1, and so as to leave an intermediate layer between the depths e1 and e2, in which intermediate layer protons incorporated during the proton exchange step remain. The depth e2 defines a thin layer between the free face and the intermediate layer. A heat treatment is carried out under conditions suitable for embrittling the intermediate layer and the thin film is separated from the first substrate at the intermediate layer.

Abstract: A guiding element suitable for integrated optics and transmission in the visible wavelength region includes a plurality of sub-wavelength sized regions in two parallel periodic arrangements embedded within a waveguide layer located on a planar substrate. The dielectric constant of each regions may be the same but different from that of the substrate, the waveguide layer, and the cladding. The periodicity, dimensions and shape of the regions of the periodic arrangement are selected to achieve the desired transmission and guiding of the incident radiation spectrum (e.g., parallel to the two periodic arrangements). A transparent layer with a dielectric constant between the dielectric constant of the periodic arrangement and the dielectric constant of the substrate/cladding provides confinement normal to the substrate.

Abstract: A photonic device and methods of formation that provide an area providing reduced optical coupling between a substrate and an inner core of the photonic device are described. The area is formed using holes in the inner core and an outer cladding. The holes may be filled with materials which provide a photonic crystal. Thus, the photonic device may function as a waveguide and as a photonic crystal.

Abstract: Provided is a mode converter capable of efficiently coupling or emitting light having a single-peaked spot, and has high flexibility of the shape to be easily manufactured. The mode converter is formed of multiple single-mode waveguides optically coupling areas 1 and 2; when an axis parallel to a light propagation direction is z axis, an axis perpendicular to the z axis in a direction crossing the single-mode waveguides is x axis, an axis perpendicular to the x and z axes is y axis, and a plane passing through a center of the mode converter and includes the z axis is plane 1, the multiple single-mode waveguides are arranged reflection-symmetrically with respect to the plane 1; and the mode converter converts light entering from the area 1 into the even mode to cause the light of the even mode to propagate and couple optically with the area 2.

Abstract: There is provided an optical waveguide comprising an optical core having transverse sides, the optical core extending along a curved path; an optical cladding on the transverse sides of the optical core, wherein the distribution of the optical cladding on the transverse sides of the optical core is asymmetric about the centre of the core.

Abstract: An optical connection structure which permits easy and automatic alignment between the optical axes of optical fibers and the optical axes of cores of an optical waveguide, and a production method which ensures that an optical waveguide for the optical connection structure can be efficiently produced with higher dimensional accuracy are provided. An over-cladding layer of the optical waveguide includes an extension portion provided in a longitudinal end portion thereof, and optical fiber fixing grooves are provided in the extension portion as extending along extension lines of cores coaxially with the cores and each having opposite ends, one of which is open in an end face of the extension portion and the other of which is closed. Optical fibers are fitted and fixed in the respective optical fiber fixing grooves. The over-cladding layer further includes a boundary portion (6) provided between the other closed ends of the optical fiber fixing grooves and the cores.

Abstract: Provided are an opto-electric hybrid board and a manufacturing method. The opto-electric hybrid board includes an optical waveguide unit and an electric circuit unit having an optical element mounted thereon. The optical waveguide unit includes socket portions for locating the electric circuit unit, which are formed on a surface of an undercladding layer and formed of the same material as a core. The socket portions are located at predetermined locations with respect to one end surface of a core. The electric circuit unit includes bent portions which are formed by bending a part of an electric circuit board so as to stand, for fitting into the socket portions. The bent portions are located at predetermined locations with respect to the optical element. The optical waveguide unit and the electric circuit unit are coupled in a state in which the bent portions fit into the socket portions.

Abstract: The system includes a light-transmitting medium positioned on a base. The light-transmitting medium included a ridge and a slab region. The ridge extends upward from the slab region and defines a portion of a waveguide on the base. The waveguide is configured to guide a light signal through the device. The device also includes an avalanche effect light sensor positioned on the base and configured to detect the presence of the light signal. The light sensor includes a light-absorbing medium positioned on the ridge of the light-transmitting medium such that the light signal is coupled from the light-transmitting medium into the light-absorbing medium. The light-transmitting includes a charge layer located at an interface of the light-transmitting medium and the light-absorbing medium. A multiplication region is formed in the slab regions of the light-transmitting medium such that the multiplication region receives charge carriers from the charge layer during the operation of the light sensor.

Abstract: The invention includes optical signal conduits having rare earth elements incorporated therein. The optical signal conduits can, for example, contain rare earth elements incorporated within a dielectric material matrix. For instance, erbium or cerium can be within silicon nanocrystals dispersed throughout dielectric material of optical signal conduits. The dielectric material can define a path for the optical signal, and can be wrapped in a sheath which aids in keeping the optical signal along the path. The sheath can include any suitable barrier material, and can, for example, contain one or more metallic materials. The invention also includes methods of forming optical signal conduits, with some of such methods being methods in which the optical signal conduits are formed to be part of semiconductor constructions.

Abstract: A process to manufacture a semiconductor optical modulator is disclosed, in which the process easily forms a metal film including AuZn for the p-ohmic metal even a contact hole has an enhanced aspect ration. The process forms a mesa including semiconductor layers first, then, buries the mesa by a resin layer sandwiched by insulating films. The resin layer provides an opening reaching the top of the mesa, into which the p-ohmic metal is formed. Another metal film including Ti is formed on the upper insulating film along the opening.

Abstract: A channeled substrate for forming integrated optical devices that employ optical fibers and at least one active optical component is disclosed. The channeled substrate includes a substrate member having an upper surface one or more grooves formed therein, and a transparent sheet. The transparent sheet, which is preferably made of thin glass, is fixed to the substrate member upper surface to define, in combination with the one or more grooves, one or more channels. The channels are each sized to accommodate an optical fiber to allow for optical communication through the transparent sheet between the active optical component and the optical fibers. Channeled substrates formed by molding and by drawing are also presented. Integrated optical devices that employ the channeled substrate are also disclosed.

Abstract: The present invention is a method and an apparatus for dynamic manipulation and dispersion in photonic crystal devices. In one embodiment, a photonic crystal structure comprises a substrate having a plurality of apertures formed therethrough, a waveguide formed by “removing” a row of apertures, and a plurality of pairs of lateral electrical contacts, the lateral electrical contact pairs extending along the length of the waveguide in a spaced-apart manner. The lateral electrical contact pairs facilitate local manipulation of the photonic crystal structure's refractive index. Thus, optical signals of different wavelengths that propagate through the photonic crystal structure can be dynamically manipulated.

Abstract: Instead of monitoring the optical power coming out of a waveguide, a direct method of monitoring the optical power inside the waveguide without affecting device or system performance is provided. A waveguide comprises a p-i-n structure which induces a TPA-generated current and may be enhanced with reverse biasing the diode. The TPA current may be measured directly by probing metal contacts provided on the top surface of the waveguide, and may enable wafer-level testing. The p-i-n structures may be implemented at desired points throughout an integrated network, and thus allows probing of different devices for in-situ power monitor and failure analysis.

Abstract: A light transmission assembly includes a light circuit board and a light transmission module. The board is embedded with waveguide layers, the waveguides layers includes core wires and shielding lays sandwiching the core wires, the waveguide layers defines a second light port portion of which the core wires defines vertical end faces. The light transmission module includes a base and a first light port portion projecting from a first face of the base, the first light port portion defines vertical end faces, the base defines a slanting surface at a second face opposite to the first face thereof. The first and second light port portions are aligned with each other when the light transmission module is coupled with light circuit board so that light lines go directly from the core wires through the light transmission module and reflect at the slant surface.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.