Abstract: Three structures, and processes for manufacturing them, that improve the performance of a TAMR feature in a magnetic write head are disclosed. This improvement is achieved by making the separation between the edge plasmon generator and the plasmon shield less than the separation between the edge plasmon generator and the optical wave-guide.

Abstract: A magnetic data recording system employing a slider having a laser diode mounted to a side surface of the slider rather than to a back surface opposite the air bearing surface. The laser diode provides a light source for thermal assisted recording. Locating the laser diode at the side surface eliminates the possibility of contact between laser diodes of adjacent sliders and allows larger, more powerful laser diodes to be employed. In addition, placing the laser diode at the side allows a micro-actuator to be attached to the back side surface of the slider, thereby allowing both thermally assisted recording and micro-actuation to be used in the same recording system.

Abstract: A plasmon-generator of the invention is configured to include a first configuration member including a near-field light generating end surface; and a second configuration member joined and integrated with the first configuration member and not including the near-field light generating end surface. The first configuration member is configured to contain Au as a primary component and to contain any one or more elements selected from a group of Co, Fe, Sb, Nb, Zr, Ti, Hf, and Ta, and is configured so that a content percentage X1 of the contained element is within a range between 0.2 at % or more and 2.0 at % or less. Thereby, thermostability, optical characteristic, and the process stability are satisfied. Also, heat dissipation and heat generation suppression effect are extremely superior.

Abstract: A driver circuit configured to generate a drive signal for an optical source comprises an overshoot controller that provides an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal. The drive signal may alternate between a first logic state associated with a first operating mode of the optical source and a second logic state associated with a second operating mode of the optical source. The overshoot controller may be configured to provide amounts of overshoot for respective instances of the first logic state that are proportional to the durations of their respective immediately preceding second logic states. The driver circuit may be implemented in a heat-assisted magnetic recording system in which the optical source alternates between on and off states associated with respective magnetic write and magnetic read modes.

Abstract: A driver circuit for a laser diode or other optical source comprises a controllable termination for a transmission line coupled between the driver circuit and the optical source, with the controllable termination being switchable between at least first and second termination configurations. The transmission line comprises a first conductor coupled to a first terminal of the optical source and a second conductor coupled to a second terminal of the optical source, and the driver circuit comprises a first current source configured to drive the first conductor, and a second current source configured to drive the second conductor. By way of example, the first termination configuration may comprise an alternating current (AC) termination configuration and the second termination configuration may comprise a direct current (DC) termination configuration.

Abstract: A data storage media may have at least a multi-layer recording lamination with a predetermined coercivity. The multi-layer recording lamination can be configured to record at least one servo format mark for a plurality of data tracks with a solid immersion mirror and program a data bit on the multi-layer recording lamination with a near field transducer.

Abstract: The present invention provides a thermally assisted magnetic head with improved recording performance. The thermally assisted magnetic head includes a recording element and a near-field light generating element. The recording element includes a main pole appearing on a medium-facing surface, and a bit inversion starting region intended to be a maximum recording magnetic field generating position is formed at a leading edge of the main pole. The near-field light generating element is located on a leading side of the main pole and capable of creating a heating spot due to a near-field light on a near-field light generating end face appearing on the medium-facing surface. The bit inversion starting region is located within one-half of a diameter of the heating spot from a center of the heating spot.

Abstract: An apparatus includes a magnetic recording layer and a thermally active material adjacent to and/or embedded in the magnetic recording layer, wherein the thermally active material has a thermal property that changes when the temperature of the thermally active material changes, or undergoes a phase transition in a predetermined temperature range, to reduce a peak temperature or increase a thermal gradient of a heated portion of the magnetic recording layer.

Abstract: A TAMR (Thermal Assisted Magnetic Recording) write head uses the energy of optical-laser excited surface plasmons in a scalable planar plasmon generator to locally heat a magnetic recording medium and reduce its coercivity and magnetic anisotropy. The planar plasmon generator is formed as a multi-layered structure in which one planar layer supports a propagating surface plasmon mode that is excited by evanescent coupling to an optical mode in an adjacent waveguide. A peg, which can be a free-standing element or an integral projection from one of the layers, is positioned between the ABS end of the generator and the surface of the recording medium, confines and concentrates the near field of the plasmon mode immediately around and beneath it.

Abstract: The wavelength is monitored using a spectrum analyzer in a state where a semiconductor laser is being driven while changing the light-emitting time of the semiconductor laser. When the internal temperature of the semiconductor laser estimated from a measured wavelength falls out of a preset temperature range, a gimbal assembly is identified as a defective product.

Abstract: A plasmon generator configured to excite a surface plasmon based on light includes a first portion formed of a first metal material and a second portion formed of a second metal material different from the first metal material. The plasmon generator has a front end face. The front end face includes a near-field light generating part that generates near-field light based on the surface plasmon. The second portion includes an end face located in the front end face. The second metal material satisfies at least one of the following requirements: a lower ionization tendency than that of the first metal material; a lower electrical conductivity than that of the first metal material; and a higher Vickers hardness than that of the first metal material.

Abstract: An apparatus includes a write pole, a waveguide adjacent to the write pole, the waveguide having a truncated end, and a blocking layer positioned adjacent the truncated end and extending from one side of the waveguide across a portion of an aperture at the truncated end. The waveguide can be a solid immersion minor or a channel waveguide.

Abstract: An apparatus includes a waveguide configured to deliver light to a transducer region. The apparatus also includes a plasmonic transducer that has two metal elements configured as side-by-side plates on a substrate-parallel plane with a gap therebetween. The gap is disposed along the substrate-parallel plane and has an input end disposed proximate the transducer region and an output end. The transducer is configured to provide a surface plasmon-enhanced near-field radiation pattern proximate the output end in response to the light received by the waveguide.

Abstract: A thermally-assisted magnetic recording head that includes a pole that generates a writing magnetic field, a waveguide through which light propagates, a plasmon generator that surface-evanescent-couples with the light propagating through the waveguide, wherein the plasmon generator includes a portion where a cross-sectional area gradually decreases as going toward a depth side from an air bearing surface when being observed from a cross section parallel to the air bearing surface. The volume of the plasmon generator can be decreased and an exposed area of a front surface on the air bearing surface can be increased. When a thermal expansion from the temperature increase occurs in the plasmon generator, a rate that the plasmon generator projects from the air bearing surface is suppressed to extremely low levels. Accordingly, a chronological degradation of output can be suppressed and thermally-assisted recording having a high and long-term reliability is achieved.

Abstract: A thermally-assisted recording (TAR) disk drive that uses “shingled” recording and a rectangular waveguide as a “wide-area” heat source includes a controller that counts the number of writes to each annular band of data tracks. The wide-area heater generates a heat spot that extends across multiple tracks, so that each time an annular band is written, the data in tracks in adjacent bands are also heated. Because the bands are written independently, the number of passes of the heat spot and thereby the number of times the data tracks in a band are exposed to elevated temperatures without being re-written is related to the number of re-writes of the adjacent bands. The number of writes to each band is counted and when that count reaches a predetermined threshold value, one or more tracks in an adjacent band are re-written to avoid reaching an unacceptable level of magnetization decay in the tracks of the adjacent band.

Abstract: A thermally-assisted recording (TAR) disk drive uses “shingled” recording and a rectangular waveguide as a “wide-area” heat source. The waveguide generates a generally elliptically-shaped optical spot that heats an area of the recording layer extending across multiple data tracks. The waveguide core has an aspect ratio (cross-track width to along-the track thickness) that achieves the desired size of the heated area while locating the peak optical intensity close to the trailing edge of the write pole tip where writing occurs. The large cross-track width of the waveguide core increases the volume of recording layer heated by the optical spot, which reduces the rate of cooling. This moves the peak temperature point of the heated area closer to the write pole tip and reduces the temperature drop between the peak temperature and the temperature at the trailing edge of the write pole tip where writing occurs.

Abstract: A thermally-assisted magnetic recording head, includes: a pole that generates a writing magnetic field from an end surface that forms a portion of an air bearing surface opposing a magnetic recording medium; a waveguide through which light for exciting a surface plasmon propagates; a plasmon generator that couples to the light in a surface plasmon mode and generates near-field light from a near-field light generating portion on a near-field light generating end surface that forms the portion of the air bearing surface; and magnetic field focusing parts that are able to focus the writing magnetic field generated from the pole and that are disposed on both sides of the pole in a track width direction from a perspective of the air bearing surface side.

Abstract: A thermally-assisted magnetic recording (TAMR) medium of the present invention includes: a magnetization direction arrangement layer on a substrate; and a magnetic recording layer on the magnetization direction arrangement layer, wherein the magnetization direction arrangement layer is made of at least one selected from a group consisting of Co, Zr, CoZr, CoTaZr, CoFeTaZrCr, CoNbZr, CoNiZr, FeCoZrBCu, NiFe, FeCo, FeAlN, (FeCo)N, FeAlSi, and FeTaC so that a spreading of the heating spot applied from the magnetic head for thermally-assisted recording to the film surface of the magnetic recording medium is suppressed, and that an SN is improved by arranging the magnetization direction of the perpendicularly written recording magnetization to become identical to a perpendicular direction, and realizing the higher recording density.

Abstract: An apparatus includes a recording media including a substrate, a plurality of tracks of magnetic material on the substrate, and a non-magnetic material between the tracks; a recording head having an air bearing surface positioned adjacent to the recording media, and including a magnetic pole, an optical transducer, and a near-field transducer, wherein the near-field transducer directs electromagnetic radiation onto tracks to heat portions of the tracks and a magnetic field from the magnetic pole is used to create magnetic transitions in the heated portions of the tracks; and a plasmonic material positioned adjacent to the magnetic material to increase coupling between the electromagnetic radiation and the magnetic material.

Abstract: An apparatus includes a transducer assembly including a waveguide and a grating structured to couple electromagnetic radiation into the waveguide, and a laser module including a laser diode and a transparent cover adjacent to an output facet of the laser diode, wherein the laser module is bonded to the transducer assembly and the laser diode directs electromagnetic radiation through the transparent cover and onto the grating. A method of making the apparatus is also provided.

Abstract: An apparatus and associated method for a head gimbal assembly for data transduction in a data storage device with a heat assist laser. Various embodiments of the present invention are generally directed to a slider supporting at least a transducing element on an air bearing surface (ABS) and a laser assembly directly attached to a top side of the slider opposite the ABS. The laser assembly is positioned on the top side with no portion of the laser assembly extending past a longitudinal centerline of the slider.

Abstract: High density-information storage is accomplished by the use of novel, near-field optical devices in combination with high-density storage media. The near-field optical devices are configured to focus light to nanoscale spot sizes and may employ negative index of refraction materials for focusing. The high-density storage media may include protein-based storage media, such as photochromic proteins, and high-coercivity magnetic storage media. Light energy provided the optical devices may enable exposed protein molecules to transition between stable molecular states that may be distinguished on the basis of their respective spectral maxima. Light energy provided by the optical device may also be used to heat localized regions of magnetic media to a selected temperature, effecting local changes in coercivity of the magnetic media.

Abstract: A thermally assisted magnetic recording medium having a structure in which a first magnetic layer 106 and a second magnetic layer 107 are formed on a substrate 101 in this order, wherein the first magnetic layer 106 has a granular structure containing a FePt alloy having a L10 structure, a CoPt alloy having a L10 crystal lattice structure or a CoPt alloy having a L11 crystal lattice structure, and at least one material for causing grain boundary segregation selected from the group consisting of SiO2, TiO2, Cr2O3, Al2O3, Ta2O5, ZrO2, Y2O3, CeO2, MnO, TiO, ZnO, and MgO, and the content of the material for causing grain boundary segregation in the first magnetic layer 106 is decreased from the substrate side to the second magnetic layer 107 side.

Abstract: Various embodiments of the present invention provide systems and methods for data writing. As an example, a heat assisted loopback circuit is discussed that includes: a read circuit, a magnetic write circuit, a heat write circuit, and a loopback circuit. The read circuit is operable to sense data from a storage medium, and to provide the sensed data as a read output. The magnetic write circuit is operable to provide a write output corresponding to an excitation signal of a write head. The heat write circuit is operable to provide a heat output corresponding to an excitation signal of a heat source. The loopback circuit is operable to selectively couple a derivative of the heat output to the read output and to selectively couple a derivative of the write output to the read output.

Abstract: A thermally-assisted magnetic recording head includes: a pole that generates a writing magnetic field from an end surface that forms a part of an air bearing surface that opposes a magnetic recording medium; a waveguide that propagates light to excite surface plasmon; and a plasmon generator that is provided between the pole and the waveguide and that generates near-field light from a near-field light generating end surface that forms a part of the air bearing surface by coupling with the light in a surface plasmon mode. The plasmon generator includes a flat plate part and a projection part that projects from the flat plate part to the waveguide side and is provided closer to a trailing side than the pole is.

Abstract: Various embodiments of the present invention provide systems and methods for data writing. As an example, a heat assisted data write circuit is discussed that includes a heat write output, a magnetic write output, and a variable phase shift circuit operable to modify a relative phase of the heat write output to the magnetic write output.

Abstract: An optical element and an information storage device including the same. The optical element may include an optical waveguide structure for transforming circularly polarized light into plasmon and transmitting the plasmon. The optical waveguide structure may emit a circularly polarized plasmonic field. The optical element may be used in an information storage device. For example, the information storage device may include a recording medium and a recording element for recording information on the recording medium, and the recording element may include the optical element. The information may be recorded on the recording medium by using the circularly polarized plasmonic field generated by the optical element.

Abstract: An apparatus and associated method is presently disclosed for a control circuitry capable of managing a heat source used in data storage applications. Various embodiments of the present invention are generally directed to a heat source directed at a data storage medium with a synchronization signal and a serial interface that are each selectively activated via a demultiplexed write gate signal. The selective activation allows for pulsed operation of the heat source resulting in reduced duty cycle and temperature during a write operation.

Abstract: A microwave assisted magnetic head of the present invention includes: at least two or more auxiliary coils that are arranged in a periphery of a writing main pole; and microwave current supply means that applies microwave currents to the at least two or more auxiliary coils. The at least two or more auxiliary coils respectively include linear body parts linearly arranged on an ABS side, two of the linear body parts of the at least two or more auxiliary coils are arranged in a substantially orthogonal positional relationship, and the microwave current supply means is configured such that the microwave current supply means changes phase differences of the microwave currents applied respectively to the at least two or more auxiliary coils. Therefore, the microwave current can be easily controlled, and thus, a circularly polarized magnetic field with high magnetization inversion efficiency can be generated as an assistance magnetic field.

Abstract: A heat-assisted magnetic write head includes a magnetic pole having an end surface exposed at an air bearing surface, a waveguide extending toward the air bearing surface to propagate light, a first pair of clads made of a first dielectric material having a refractive index lower than that of the waveguide, and sandwiching the waveguide in a track width direction, and a second pair of clads made of a second dielectric material having a refractive index lower than that of the first dielectric material, and sandwiching the waveguide in a thickness direction orthogonal to the track width direction. Further, the heat-assisted magnetic write head may include, between the magnetic pole and the waveguide, a plasmon generator generating near-field light from the air bearing surface, based on light propagating through the waveguide.

Abstract: A thermally-assisted magnetic recording method includes first and second steps. The first step applies heat to part of a hard disk medium and forms a moving high-temperature region in a magnetic recording layer of the hard disk medium. The high-temperature region is higher in temperature than a region therearound and has a temperature equal to or higher than the maximum coercivity vanishing temperature of a plurality of magnetic grains contained in the magnetic recording layer. At least one magnetic grain that is adjacent to the rear end of the high-temperature region in the direction of movement of the high-temperature region has a coercivity of a value other than 0. The second step applies a write magnetic field to the hard disk medium such that the write magnetic field applied to the at least one magnetic grain adjacent to the rear end of the high-temperature region is 3 kOe or smaller in magnitude.

Abstract: A metal film is included which is placed between a core and a cladding, propagates a laser beam along an interface between the core and the cladding, and generates a near-field light from the laser beam. The metal film has a base portion placed on one side surface of the core along a propagation direction of the laser beam facing from one end side toward the other end side, and an extending portion extended from the other end side of the base portion to the other end side in the propagation direction rather than the core. The other end side of the extending portion is exposed to the outside, and is formed with a top portion projected toward the core side when viewed from the propagation direction.

Abstract: A heat-assisted magnetic write head includes a magnetic pole having an end surface exposed at an air bearing surface, a waveguide extending toward the air bearing surface to propagate light, and a plasmon generator provided between the magnetic pole and the waveguide, and generating near-field light from the air bearing surface, based on the light propagated through the waveguide. The plasmon generator has an end portion exposed at the air bearing surface or located in close proximity to the air bearing surface, the end portion having a minimum thickness in a region close to the waveguide.

Abstract: A magneto-optical device (MOD) with optically induced magnetization for use in magnetic field sensors as a magnetic element pinning a magnetization in a preferred direction of a ferromagnetic layer as well as a magnetic memory cell for magneto-optical recording. The MOD comprises the Mg—Mg—Co ferrite film deposited on a magnesium oxide (MgO) substrate. The ferrite film is illuminated at room temperature with a circularly polarized light (CPL) in a static magnetic H-field (about of 3 kOe) normal to the illuminated ferrite film surface. At certain (“writing”) combinations of H, sigma (CPL helicity), the long-lived optically induced magnetization with a unidirectional anisotropy, stable to a conventional demagnetization occurs. For readout of information, conventional magnetoresistive sensors and MFM can be used. To erase information, the ferrite film should be illuminated with two field-light combinations, other than “writing”, or annealed at temperature higher than 530 degrees C.

Abstract: Changes in the thermal boundary condition near a close point of an ABS to a media indicate proximity of the ABS with the media. Before contact, heat conduction from the ABS is primarily through convective and/or ballistic heat transfer to air between the ABS and the media. After contact, heat flux primarily flows from the ABS to the media through solid-solid conductive contact. Further, a light source within a HAMR transducer head may create additional thermal variations within the transducer head. These thermal variations create temperature variations within the transducer head. Two resistance temperature sensors on the transducer head at varying distances from the close point and/or light source measure these temperature variations. A temperature difference between the two resistance temperature sensors indicates proximity of the close point to the media and/or light output.

Abstract: A method of evaluating a magnetic recording medium using a magnetic head having a reproduction element is disclosed The method includes the steps of (a) recording a signal in a predetermined area of the magnetic recording medium; (b) determining a first value of a reproduction output by reproducing the predetermined area of the magnetic recording medium; (c) determining a second value of the reproduction output by emitting an energy line having a power of a predetermined value onto the predetermined area and reproducing the predetermined area with the reproduction element during or after the emission of the energy line; and (d) calculating a change in the reproduction output due to the emission of the energy line based on the first value and the second value of the reproduction output.

Abstract: A thermally-assisted magnetic head that includes an air bearing surface facing a recording medium and that performs magnetic recording while heating the recording medium includes: a magnetic recording element including a pole of which one edge part is positioned on the air bearing surface and that generates magnetic flux traveling toward the magnetic recording medium; a waveguide configured with a core through which light propagates and a cladding, at least one part of which extends to the air bearing surface, surrounding the periphery of the core; a plasmon generator that faces a part of the core and that extends to the air bearing surface.

Abstract: In accordance with certain embodiments, an apparatus has a depletion-mode transistor electrically connected to a laser diode. The transistor provides a low impedance path for diverting electrostatic current away from the laser diode. In accordance with certain embodiments, a method for protecting a laser diode from an electrostatic charge includes providing a transistor that is electrically connected to a laser diode and has a drain and a source. The method further includes redirecting the electrostatic charge through a low impedance path from the drain to the source during a powered-on state.

Abstract: An aspect of the disclosure relates to data storage heater systems with diodes. In one embodiment, data storage systems include a first electrical connection point, a second electrical connection point, a first electrical branch, and a second electrical branch. The first electrical branch is connected to the first and the second electrical connection points. The first electrical branch has first and second diodes biased in a first direction. The second electrical branch is connected to the first and second electrical connection points. The second electrical branch has third and fourth diodes biased in a second direction.

Abstract: In accordance with certain embodiments, a magnetic head has a coil, which has a lead coil turn positioned between a yoke and an air-bearing surface. In certain embodiments, a magnetic head has a coil, which has a lead coil turn minimally spaced from a main write pole.

Abstract: A plurality of laser diode units is tested in a bar state, each of the laser diode units in which a laser diode that includes a first electrode and a second electrode formed on surfaces facing each other and that is mounted on a mounting surface of a submount such that the first electrode faces the mounting surface of the submount.

Abstract: A thermally-assisted magnetic head that has an air bearing surface (ABS) facing a recording medium and that performs magnetic recording while heating the recording medium includes: a magnetic recording element that includes a pole of which an edge part is positioned on the ABS and which generates magnetic flux traveling to the recording medium; a waveguide that is configured with a core through which light propagates and a cladding, surrounding a periphery of the core, at least one part of which extends to the ABS; a plasmon generator that faces a part of the core and that extends toward the ABS side; and a bank layer that is positioned between the plasmon generator and the pole, and of which an edge part on the ABS side protrudes relative to the plasmon generator.

Abstract: A hard disk drive includes a recording medium and a thermally assisted type magnetic head. The controller determines one output current of a photodiode as a first saturated output current, the one output current being defined where temperature measured by a temperature sensor is a first temperature and where signal-to-noise-ratio (SNR) of the reproducing signal current of the reproducing element is saturated with respect to an increase in output current of the photodiode, and another output current of the photodiode as a second saturated output current, the another output current being defined where temperature measured by the temperature sensor is a second temperature, which is different from the first temperature, and where SNR of the reproducing signal current of the reproducing element is saturated with respect to an increase in the output current of the photodiode.

Abstract: In a thermally assisted recording head using a conductive scatterer as an optical near-field transducer, a propagation loss in a waveguide for guiding light to the scatterer is reduced. An optical near-field is generated by using the conductive scatterer having a width that gradually becomes smaller toward a vertex at which the optical near-field is generated. At the same time, a height of the conductive scatterer for generating the optical near-field is made substantially equal to a height of a main pole or longer than the height of the main pole.

Abstract: A write head includes a cavity configured to couple a laser diode to the write head. A bottom of the cavity includes a heat conductive element configured to contact the laser diode, a plurality of thermal studs disposed below the heat conductive element, and a substrate disposed below the thermal studs. The heat conductive element, thermal studs, and substrate are thermally coupled to draw heat from the laser diode.

Abstract: A magneto-optical transducer including a magnetic layer on a transparent, non-magnetic substrate is used to characterize the performance of a write head based on optically detected magnetization in the magnetic layer. The write head sample is held in contact with or near the magnetic layer, which is illuminated through the substrate with linearly polarized light. Magnetization in the write head produces a magnetization in the magnetic layer, which alters the polarization state in reflected light. The reflected light is analyzed and the intensity detected using an optical detector, such as one or more photo-detectors or a camera. The performance of the write head can then be characterized using the detected intensity.

Abstract: A thermally assisted magnetic head is formed by performing a head forming process, a mounting part forming process and a light source mounting process in that order. In the head forming process, a planned area is secured on a light source placing surface of a slider substrate, then a magnetic head part is formed on a head area other than the planned area and a spacer for securing a mounting space for the laser diode is formed on the planned area. In the mounting part forming process, a light source mounting part is formed by removing the spacer. In the light source mounting process, a laser diode is mounted on the light source mounting part formed by the mounting part forming step.

Abstract: An optical waveguide of the invention includes a core that is a waveguide through which light propagates; and a cladding that surrounds the core. The core has a plate shape and includes a wide core base part onto which the light is incident, a taper part that is connected to the core base part and of which a width is gradually tapered along a propagation direction, and a narrow front end core part that is connected to the taper part and that extends along the propagation direction.

Abstract: A TAMR head is disclosed with a triangular shaped plasmon antenna covered on two sides with a plasmon layer that generates an edge plasmon mode along a vertex of the two plasmon sides formed opposite a main pole layer. A plasmon shield (PS) is formed along the ABS and opposite the vertex to confine an electric field from the edge plasmon mode within a small radius of the edge plasmon tip thereby reducing the optical spot size on the magnetic medium and enhancing writability. An end of a waveguide used to direct input electromagnetic radiation to the plasmon antenna adjoins a PS side opposite the ABS. In one embodiment, a magnetic shield may be formed along the ABS and adjoins the PS so that a first PS section terminates at the ABS and faces the vertex while a second PS section is formed between the magnetic shield and waveguide end.

Abstract: Provided is a near-field light emitting device which emits near-field light efficiently by simple structure. A near-field light emitting device comprises a waveguide which is equipped with a core and a clad touching the core and is coupled with light having an electric field component in the direction perpendicular to the boundary surface of the core and clad, and a planar metal structure which is arranged along the above-mentioned boundary surface where the electric field component is in the perpendicular direction. The metal structure has a tip adjoining the light exit surface of the core, and a side projecting to the clad where the width of the metal structure in the direction perpendicular to the propagation direction of the light coupled with the waveguide is wider than the width of the core.