WO2014084368A1 - Laser light source - Google Patents

Laser light source Download PDF

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Publication number
WO2014084368A1
WO2014084368A1 PCT/JP2013/082230 JP2013082230W WO2014084368A1 WO 2014084368 A1 WO2014084368 A1 WO 2014084368A1 JP 2013082230 W JP2013082230 W JP 2013082230W WO 2014084368 A1 WO2014084368 A1 WO 2014084368A1
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WO
WIPO (PCT)
Prior art keywords
semiconductor laser
optical waveguide
light source
laser light
substrate
Prior art date
Application number
PCT/JP2013/082230
Other languages
French (fr)
Japanese (ja)
Inventor
薫 依田
まゆみ 影山
昌史 井出
Original Assignee
シチズンホールディングス株式会社
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Application filed by シチズンホールディングス株式会社 filed Critical シチズンホールディングス株式会社
Priority to JP2014549927A priority Critical patent/JPWO2014084368A1/en
Publication of WO2014084368A1 publication Critical patent/WO2014084368A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/125—Bends, branchings or intersections
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/365—Non-linear optics in an optical waveguide structure
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/37—Non-linear optics for second-harmonic generation
    • G02F1/377—Non-linear optics for second-harmonic generation in an optical waveguide structure
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12083—Constructional arrangements
    • G02B2006/12121—Laser
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
    • G02F1/3509—Shape, e.g. shape of end face
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0092—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/023—Mount members, e.g. sub-mount members
    • H01S5/02325—Mechanically integrated components on mount members or optical micro-benches
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/0235—Method for mounting laser chips
    • H01S5/02355—Fixing laser chips on mounts
    • H01S5/0237—Fixing laser chips on mounts by soldering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1082—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region with a special facet structure, e.g. structured, non planar, oblique
    • H01S5/1085—Oblique facets

Definitions

  • the present invention relates to a laser light source for converting the wavelength of laser light from a semiconductor laser and emitting the converted light.
  • a semiconductor laser and an optical waveguide type wavelength conversion element (hereinafter also referred to as "SHG element"), and the outgoing surface of the active layer of the semiconductor laser and the incident surface of the optical waveguide of the SHG element are directly coupled to submicron order Laser light sources that have been approached or in close proximity have been proposed.
  • an edge-emitting semiconductor laser is provided inexpensively by forming a laser resonator by dividing a large substrate (wafer) into a large number using dicing and cleaving in order to improve mass productivity.
  • the end face including the emission face is an inclined cleavage plane which is inclined due to the crystal orientation.
  • FIG. 8A is a cross-sectional view of a conventional laser light source 20 using a semiconductor laser 22 having an inclined cleavage plane.
  • the laser light source 20 includes a substrate 21, a semiconductor laser 22, and an SHG element 23.
  • the semiconductor laser 22 and the SHG element 23 are mounted face-down on the substrate 21 to improve the heat dissipation characteristics, the semiconductor laser 22 is fixed by gold-tin solder, and the SHG element 23 is fixed by an adhesive.
  • the exit surface 222 of the active layer 221 of the semiconductor laser 22 and the entrance surface 232 of the optical waveguide 231 of the SHG element 23 are in close proximity to each other on the micron order by direct coupling.
  • the semiconductor laser 22 emits an infrared laser beam from the emission surface 222 of the active layer 221, and the laser beam enters the incident surface 232 of the optical waveguide 231 of the SHG element 23.
  • the SHG element 23 converts the wavelength of the incident laser light while propagating the light through the optical waveguide 231 and emits the light as green light or blue-violet light.
  • FIG. 8B is an enlarged partial cross-sectional view of a butt coupling portion C of the semiconductor laser 22 and the SHG element 23 in FIG. 8A.
  • the incident end face 233 of the SHG element 23 including the incident surface 232 of the optical waveguide 231 is perpendicular to the bottom surface of the SHG element 23.
  • Patent Document 1 proposes a laser light source in which the influence of heat radiation from the semiconductor laser to the SHG element is reduced by inclining a part of the incident surface of the SHG element with respect to the emission surface of the semiconductor laser.
  • FIG. 9A is a cross-sectional view of the laser light source 30 of Patent Document 1. As shown in FIG. 9B is an enlarged partial cross-sectional view of butt coupling portion D of semiconductor laser 32 and SHG element 33 in FIG. 9A.
  • the laser light source 30 has a substrate 31, a semiconductor laser 32, and an SHG element 33, as in the laser light source 20 shown in FIGS. 8A and 8B.
  • the incident surface 332 of the optical waveguide 331 and the emission surface 322 of the semiconductor laser 32 are perpendicular to the substrate 31 instead of the inclined surface, and face each other in parallel.
  • the semiconductor laser 32 and the SHG element 33 can be disposed close to each other, and good coupling efficiency can be obtained. Furthermore, in the laser light source 30, since the end face 333 of the substrate 330 of the SHG element 33 facing the semiconductor laser 32 is an inclined surface, the radiation heat from the semiconductor laser 32 is not easily transmitted to the SHG element 33, and the temperature of the SHG element 33 The rise is reduced.
  • the inclined cleavage surface 223 of the semiconductor laser 22 is inclined (overhanged) toward the SHG element 23
  • the inclined cleavage surface of the semiconductor laser 22 is The upper end 224 (the end opposite to the active layer 221) of the HG 223 abuts on the incident end face 233 of the SHG element 23. Therefore, with the laser light source 20, it is impossible to bring the exit surface 222 of the semiconductor laser 22 and the incident surface 232 of the SHG element 23 close to sub-micron order, and the coupling efficiency is significantly impaired.
  • Patent Document 1 the inclination angle is formed large in order to reduce the influence of the radiation heat from the semiconductor laser on the SHG element, and no mention is made of the inclined cleavage plane of the semiconductor laser 32. .
  • a butt coupling portion of the substrate 330 of the SHG element 33 is formed with an inclined surface with a large angle ⁇ 1, dust and the like are easily caught in the gap of the coupled portion, which interferes with the emitted light.
  • Another object of the present invention is to allow butt-coupling between the exit surface of the active layer of a semiconductor laser having a tilted cleavage surface and the entrance surface of the optical waveguide of the optical waveguide type wavelength conversion element to approach submicron order.
  • Another object of the present invention is to provide a high-power laser light source in which the coupling efficiency between a semiconductor laser and an optical waveguide type wavelength conversion element is improved.
  • the laser light source has a substrate, a semiconductor laser and an optical waveguide type wavelength conversion element, and the emission surface of the active layer of the semiconductor laser and the incident surface of the optical waveguide of the optical waveguide type wavelength conversion element are directly opposed to each other.
  • the emission surface of the semiconductor laser is an inclined cleavage surface having an inclination angle which causes an overhang with the active layer on the bottom
  • the incident surface of the optical waveguide type wavelength conversion element is The light emitting device according to the present invention is characterized in that the light emitting surface of the semiconductor laser is brought close to the light incident surface of the optical waveguide type wavelength conversion element by forming the incident end face having a shape inclined according to the inclination angle of the inclined cleavage surface of the semiconductor laser. .
  • the laser light source is fixed on the substrate such that the substrate, the semiconductor laser fixed on the substrate with the active layer on the bottom, and the incident surface of the optical waveguide directly face the emission surface of the active layer of the semiconductor laser.
  • the output surface of the semiconductor laser is a tilted cleavage plane
  • the optical waveguide type wavelength conversion device includes the incident plane of the optical waveguide at the inclination angle of the inclined cleavage plane of the semiconductor laser. It is characterized by having a sloped incident end face together.
  • the emission surface of the semiconductor laser be an inclined cleavage surface which is inclined so as to be an overhang with respect to the optical waveguide type wavelength conversion element.
  • the incident end face of the optical waveguide type wavelength conversion element has an inclination angle larger than the inclined cleavage surface of the semiconductor laser with respect to the plane perpendicular to the substrate.
  • the incident end face of the optical waveguide type wavelength conversion element preferably has an inclination angle of 3 ° or less with respect to a plane perpendicular to the substrate.
  • the incident end face of the optical waveguide type wavelength conversion element is preferably one plane including the incident surface of the optical waveguide.
  • the semiconductor laser and the optical waveguide type wavelength conversion element be bonded to the substrate by a surface activation bonding technique through a bonding portion having a micro bump structure made of Au.
  • the above laser light source it is possible to butt-couple the emission surface of the active layer of the semiconductor laser having the inclined cleavage plane and the incident surface of the optical waveguide of the optical waveguide type wavelength conversion element to approach submicron order. It becomes. Furthermore, according to the above laser light source, the coupling efficiency between the semiconductor laser and the optical waveguide type wavelength conversion element is improved, and high output can be obtained.
  • FIG. 2 is a perspective view of a laser light source 1;
  • FIG. 2 is a cross-sectional view of the laser light source 1 taken along line AA in FIG. 1 and an enlarged partial cross-sectional view of a butt coupling portion B.
  • FIG. FIG. 2 is a cross-sectional view of a semiconductor laser 12;
  • FIG. 5 is an enlarged partial cross-sectional view of a butt coupling portion of a laser light source 1 ′ in which the semiconductor laser 12 is mounted in a direction opposite to that of the laser light source 1.
  • FIG. 7 is a process diagram for describing a manufacturing process of the SHG element 13 of the laser light source 1;
  • FIG. 6 is a process diagram for describing a manufacturing process of the SHG element 13 following FIG. 5.
  • FIG. 1 It is an expanded fragmentary sectional view of the butt coupling part of laser light source 2, 2 '. It is sectional drawing of the conventional laser light source 20 using the semiconductor laser 22 which has an inclined cleavage plane, and an enlarged fragmentary sectional view of butt coupling part C. FIG. It is sectional drawing of the laser light source 30 of patent document 1, and an expanded fragmentary sectional view of butt coupling part D. FIG.
  • the laser light source will be described below with reference to the drawings.
  • a semiconductor laser for emitting so-called infrared light and an SHG element for converting the laser light into green light, which is a second harmonic of half wavelength, are mounted facedown on a substrate to form a semiconductor
  • An example in which the emission surface of the active layer of the laser and the incident surface of the optical waveguide of the SHG element are directly coupled will be described.
  • FIG. 1 is a perspective view of a laser light source 1.
  • FIG. 2A is a cross-sectional view of the laser light source 1 taken along the line AA in FIG. 2B is an enlarged partial cross-sectional view of butt coupling portion B of semiconductor laser 12 and SHG element 13 in FIG. 2A.
  • the laser light source 1 has a Si platform 11, a semiconductor laser 12, and an SHG element 13.
  • the Si platform 11 is a silicon substrate on which a wiring pattern, a land, a logic LSI, a temperature sensor, an optical wiring, an optical waveguide to be an optical circuit, and the like are formed.
  • the semiconductor laser 12 is made of, for example, a material such as GaAs or GaN, and when using a near-infrared GaAs laser, emits infrared laser light with a wavelength of 1064 nm from the emission surface of the active layer 121.
  • SHG element 13 for example, a LN substrate 130 made of lithium niobate (LiNbO 3), and the optical waveguide substrate 131 made of lithium niobate doped with magnesium oxide (MgO-LiNbO 3) is formed are joined.
  • the SHG element 13 converts the infrared laser light incident on the incident surface of the optical waveguide of the optical waveguide substrate 131 into a harmonic and emits green laser light G having a wavelength of 532 nm.
  • the semiconductor laser 12 is mounted on the upper surface of the Si platform 11 so-called face-down with the active layer 121 down, and fixed by gold-tin solder.
  • the SHG element 13 is also mounted face down on the top surface of the Si platform 11 with the surface of the optical waveguide substrate 131 facing down, and after alignment, it is bonded or gold-tin solder mounted.
  • the emission surface of the semiconductor laser 12 of about 2 ⁇ 2 ⁇ m and the incident surface of the SHG element 13 of about 4 ⁇ 4 ⁇ m are opposed by butt coupling, and the distance is less than 1 ⁇ m. Close to the distance of In the laser light source 1, the coupling efficiency is improved by such high-precision positioning, so that high output can be obtained.
  • the active layer 121 of the semiconductor laser 12 has an emission surface 122 for emitting laser light.
  • the emitting surface 122 of the semiconductor laser 12 is in the same plane as the inclined cleavage surface 123 inclined at an angle ⁇ 2 with respect to the plane perpendicular to the Si platform 11 due to the crystal orientation.
  • the inclined cleavage surface 123 is inclined such that the upper end 124 (the end opposite to the active layer 121) faces the SHG element 13. That is, the inclined cleavage plane 123 is inclined so as to be an overhang with respect to the SHG element 13.
  • the inclination angle ⁇ 2 of the inclined cleavage surface 123 is referred to as “cleavage inclination angle ⁇ 2”.
  • the optical waveguide 132 of the SHG element 13 has an incident surface 133 facing the output surface 122 of the semiconductor laser 12.
  • the end surfaces of the LN substrate 130 and the optical waveguide substrate 131 (optical waveguide 132) facing the semiconductor laser 12 will be referred to as the incident end surface 134 of the SHG element 13.
  • the incident end face 134 is one plane including the incident surface 133 of the optical waveguide 132 unlike the laser light source 30 of FIGS. 9A and 9B. Further, the incident end face 134 is inclined so that the upper end thereof is separated from the semiconductor laser 12 at an inclination angle ⁇ 3 slightly larger than the cleavage inclination angle ⁇ 2 in accordance with the inclined cleavage surface 123 of the semiconductor laser 12.
  • the laser light source 1 even if the cleavage inclination angle ⁇ 2 of the semiconductor laser 12 has some variations, and even if there are partial projections on the inclined cleavage surface 123, the inclined cleavage surface of the semiconductor laser 12 The upper end 124 of 123 does not abut the incident end surface 134 of the SHG element 13. Therefore, in the laser light source 1, it is possible to make the emission surface 122 of the semiconductor laser 12 and the incident surface 133 of the SHG element 13 approach each other to the submicron order by butt coupling, and high coupling efficiency can be obtained.
  • the coupling efficiency ⁇ only needs to be reduced to about 86% of that when the inclination angle ⁇ 3 is 0 ° (perpendicular surface).
  • the inclination angle ⁇ 3 of the incident end surface 134 is smaller than the cleavage inclination angle ⁇ 2 of the semiconductor laser 12, as shown in FIG.
  • the upper end 124 of the inclined cleavage surface 123 of the semiconductor laser 12 is SHG element 23 But it strikes the incident end face 134 of the Therefore, the inclination angle ⁇ 3 of the incident end surface 134 of the SHG element 13 is preferably larger than the cleavage inclination angle ⁇ 2 of the semiconductor laser 12 and within 3 °.
  • the inclination angle ⁇ 3 of the incident end surface 134 of the SHG element 13 is preferably larger than ⁇ ⁇ ⁇ 2 ° and 3 ° or less.
  • the emission surface 122 of the semiconductor laser 12 may be an inclined cleavage surface in which the upper end is inclined away from the SHG element 13.
  • the laser light source in this case will be described with reference to FIGS. 3 and 4.
  • FIG. 3 is a cross-sectional view of the semiconductor laser 12.
  • the semiconductor laser 12 in the above-described laser light source 1 uses the inclined cleavage plane 123 located on the right side of FIG.
  • the emitting surface of the semiconductor laser 12 is not limited to the inclined cleavage surface 123, and the inclined cleavage surface 123 ′ on the opposite side of the inclined cleavage surface 123 can be used similarly.
  • the inclined cleavage surfaces 123 and 123 ' are both inclined with respect to a plane perpendicular to the bottom surface of the semiconductor laser 12 at a cleavage inclination angle ⁇ 2 of the same size determined by the crystal orientation.
  • FIG. 4 is an enlarged partial cross-sectional view of a butt coupling portion of a laser light source 1 ′ in which the semiconductor laser 12 is mounted in the opposite direction to the laser light source 1.
  • the laser light source 1 ′ differs from the laser light source 1 only in the mounting direction of the semiconductor laser 12 and the inclination angle of the incident end face of the SHG element 13, and all other configurations are the same as the laser light source 1. For this reason, the description of the overlapping structural members is omitted.
  • the incident end face 134 'of the SHG element 13 is inclined such that the upper end is directed to the semiconductor laser 12 at an inclination angle ⁇ 3 slightly larger than the cleavage inclination angle ⁇ 2 in accordance with the inclined cleavage surface 123' of the semiconductor laser 12. It may be Alternatively, also in the laser light source 1 ′, the incident end face 134 ′ may be inclined so that the upper end is separated from the semiconductor laser 12 at the inclination angle ⁇ 3 as in the incident end face 134 of the SHG element 13 of the laser light source 1. However, if the angle between the emitting surface 122 'of the semiconductor laser 12 and the incident end face 134' of the SHG element 13 is too large, the coupling efficiency is degraded.
  • the inclination angle ⁇ 3 of the incident end face 134 ' is It is preferably within 3 °.
  • the emission surface 122 ′ of the semiconductor laser 12 and the incident end surface 134 ′ of the SHG element 13 when ⁇ 2 ⁇ 2 °.
  • the angle formed by is greater than 22 ° and within 3 ° + ⁇ 2 °.
  • FIGS. 5 and 6 are process diagrams for explaining the manufacturing process of the SHG element 13 of the laser light source 1.
  • the manufacturing process for forming the inclination angle ⁇ 3 on the incident end surface 134 of the SHG element 13 will be described with reference to FIGS. 5 and 6.
  • the same constituent members are denoted by the same reference numerals, and redundant description will be omitted.
  • a large LN substrate 130A made of lithium niobate (LiNbO 3 ) and a common electrode for polarization inversion and lithium niobate doped with magnesium oxide are formed.
  • the large-size optical waveguide substrate 131A made of (MgO-LiNbO 3 ) is bonded, for example, with an epoxy adhesive to form a large-size SHG substrate 13A.
  • the large-size optical waveguide substrate 131A is subjected to rough polishing, final polishing, and CMP (Chemical Mechanical Polishing) polishing to a thickness of about 4 to 5 ⁇ m, and the polished surface is a mirror surface To form a large-sized optical waveguide polishing substrate 131B.
  • CMP Chemical Mechanical Polishing
  • the large-size SHG substrate 13A is obtained by bonding the very thin large-size optical waveguide polishing substrate 131B to the large-size LN substrate 130A having a thickness of about 0.5 mm.
  • a comb electrode is formed on the large-size optical waveguide polishing substrate 131B obtained in the manufacturing step ST02, polarization inversion processing is performed, and dry etching or laser processing is further performed. Then, a large-size optical waveguide forming substrate 131C on which a large number of optical waveguides (not shown) are formed is formed.
  • the large-size SHG substrate 13A having the large-size LN substrate 130A and the large-size optical waveguide forming substrate 131C on which the optical waveguide is formed in the dicing step of the manufacturing process ST04 is parallel to the optical waveguide. Dicing is performed along dicing lines L1 in the direction and dicing lines L2 in the direction perpendicular to the optical waveguide. Thereby, a large number of SHG child substrates 13B are formed. Each SHG child substrate 13B is an assembly of SHG elements.
  • the SHG child substrate 13B diced in the manufacturing process ST04 is picked up and set in a polishing jig.
  • the SHG child substrate 13B has an LN child substrate 130B made of lithium niobate (LiNbO 3 ), and an optical waveguide child substrate 131D in which the optical waveguide 132 is formed.
  • both ends of the optical waveguide 132 of the SHG child substrate 13B shown in the manufacturing process ST05 are polished to form the LN child substrate 130C, the incident surface 133 of the optical waveguide 132, and not shown.
  • An optical waveguide substrate 131E having an exit surface is formed. That is, rough polishing, finish polishing, and CMP (Chemical Mechanical Polishing) polishing are performed on both ends of the optical waveguide of the SHG child substrate 13B to optically mirror the incident end face 134 and the emission end face (not shown) of the SHG child substrate 13B. Finish.
  • the incident end surface 134 is formed in one plane including the incident surface 133 of the optical waveguide 132, and has an inclination angle ⁇ 3 with respect to the vertical direction as shown in FIG. 2B by inclined polishing.
  • the emission end surface including the emission surface (not shown) is vertically polished and becomes perpendicular to the bottom surface of the optical waveguide substrate 131E. Further, an antireflection film is formed on the incident end surface 134 and the output end surface as an optical process.
  • inclined polishing may be performed after stacking a plurality of SHG daughter boards 13B.
  • the SHG child substrates 13B are mutually offset from each other in consideration of the length difference caused by the inclined polishing before the emission end face is vertically polished. You need to
  • dicing is performed along dicing line L3 to separate SHG child substrate 13B, which is an assembly of SHG elements, into a plurality of SHG elements 13.
  • the cutting line L3 is formed such that the optical waveguide of the SHG element 13 is disposed along the central portion.
  • an incident end face 134 which is an inclined surface including the LN substrate 130 and the optical waveguide substrate 131 and which includes the incident surface 133 is formed on the incident side of the optical waveguide, and not shown on the emission side of the optical waveguide.
  • the incident end face 134 has an inclination angle ⁇ 3 which is larger than the cleavage inclination angle ⁇ 2 (for example, ⁇ 2 °) of the semiconductor laser 12 and is within 3 °.
  • the manufacturing process of the SHG element 13 is simplified. Therefore, since the manufacturing of the SHG element 13 is easy and the number of processes can be shortened, the SHG element 13 and the laser light source 1 using the same can be provided at low cost.
  • the inclination angle ⁇ 3 by polishing is a slight inclination, the coupling efficiency of the butt coupling is hardly reduced, and it is possible to provide a high output laser light source. Furthermore, since the opening of the inclination angle ⁇ 3 by polishing is smaller than the cleavage inclination angle ⁇ 2, dust and the like hardly enter between the emission surface 122 of the semiconductor laser 12 and the incident surface 133 of the SHG element 13.
  • FIGS. 7 (a) and 7 (b) are enlarged partial sectional views of butt coupling portions of the laser light sources 2 and 2 ', respectively.
  • the laser light sources 2 and 2 ' are different from the laser light sources 1 and 1' only in the bonding method of the Si platform 11 and the semiconductor laser 12 and the SHG element 13, respectively, and all other configurations are the same as the laser light sources 1 and 1 '. is there. For this reason, the description of the overlapping structural members is omitted.
  • a silicon oxide film (not shown) is formed on the upper surface of the Si platform 11.
  • the silicon oxide film as an insulating film, insulates wiring patterns and the like other than the land portion region to which the electric element such as the semiconductor laser 12 is electrically connected.
  • the upper surface of the Si platform 11 has a large number of micro bumps made of Au in the region where the semiconductor laser 12 and the SHG element 13 are bonded.
  • Junctions 142 and 144 are formed.
  • the microbumps are, for example, cylindrical columns with a diameter of 5 ⁇ m and a height of 2 ⁇ m, and are formed with a pitch of 10 to 25 ⁇ m at the bonding portions 142 and 144.
  • Au films 141 and 143 are formed on the lower surfaces of the semiconductor laser 12 and the SHG element 13, that is, the surfaces to be bonded to the Si platform 11.
  • the semiconductor laser 12 is bonded onto the Si platform 11 by surface activation bonding of the Au film 141 and the micro bumps of the bonding portion 142.
  • the SHG element 13 is bonded onto the Si platform 11 by surface activation bonding of the Au film 143 and the micro bumps of the bonding portion 144.
  • the presence of a metal material such as Au in the vicinity of the optical waveguide adversely affects the junction 144 not to be joined to the Au film 143 over the entire lower surface of the SHG element 13. It joins in the part except the longitudinal direction of the width
  • argon plasma processing is performed on the Si platform 11, the semiconductor laser 12, and the SHG element 13 under a vacuum of 6 to 8 Pa level.
  • the oxide films covering the surfaces of the micro bumps of the junction portions 142 and 144 of the semiconductor laser 12 and the Au films 141 and 143 of the SHG element 13 and the Si platform 11 are removed, and inactive layers such as contamination (dust) are removed. , Activate their surface.
  • the semiconductor laser 12 and the SHG element 13 are mounted on the Si platform 11, and a load (for example, 5 to 10 Kgf) in a normal temperature atmosphere of 150.degree. Apply pressure by applying / mm 2 ).
  • the microbumps are slightly crushed and deformed in the thickness direction according to the load, and the Si platform 11 and the semiconductor laser 12 and the SHG element 13 are securely bonded by covalent bonding of Au atoms.
  • the heating temperature is 150 ° C. or less at the normal temperature level, even if the parts such as the semiconductor laser 12 and the SHG element 13 are bonded, the parts are broken due to the residual stress of the thermal expansion coefficient difference There is no problem of functional deterioration due to stress or positional deviation due to thermal expansion. Therefore, in the laser light source 2, the semiconductor laser 12 and the SHG element 13 can be mounted on the same substrate with high precision on the same substrate, so the coupling efficiency at the butt coupling portion between the semiconductor laser 12 and the SHG element 13 is improved. And high output can be obtained.
  • the present invention is not limited to the above-described laser light sources 1, 1 ', 2, 2', and it is not necessary to include all of the configurations thereof, within the scope of the contents described in the claims. It goes without saying that various changes or omissions may be made.
  • 1,1 ', 2,2' laser light source 11 Si platform 12 semiconductor laser 13 SHG element (optical waveguide type wavelength conversion element) 121 active layer 122, 122 'exit surface 123, 123' inclined cleavage plane 124, 124 'upper end 130 LN substrate 131 optical waveguide substrate 132 optical waveguide 133, 133' entrance surface 134, 134 'entrance end surface 141, 143 Au film 142 , 144 joints

Abstract

Provided is a laser light source capable of butt-coupling and bringing into proximity at a submicron level the emission face of the active layer of a semiconductor laser having an inclined cleavage plane, and the incident face of the optical waveguide of an optical-waveguide-type wavelength conversion element. The laser light source has: a substrate; a semiconductor laser having an active layer as the bottom face and fixed on the substrate; and the optical-waveguide-type wavelength conversion element fixed on the substrate such that the incident face of the optical waveguide is directly opposed to the emission face of the active layer of the semiconductor laser; the emission face of the semiconductor laser being an inclined cleavage plane, and the optical-waveguide-type wavelength conversion element having an inclined incident end face that conforms to the inclination angle of the inclined cleavage plane of the semiconductor laser, including the incident face of the optical waveguide.

Description

レーザ光源Laser light source
　本発明は、半導体レーザからのレーザ光を波長変換して出射するレーザ光源に関する。 The present invention relates to a laser light source for converting the wavelength of laser light from a semiconductor laser and emitting the converted light.
　半導体レーザと光導波路型波長変換素子（以下、「ＳＨＧ素子」とも称する）とを有し、半導体レーザの活性層の出射面とＳＨＧ素子の光導波路の入射面とを直接結合でサブミクロンオーダーまで接近又は密接させたレーザ光源が提案されている。 A semiconductor laser and an optical waveguide type wavelength conversion element (hereinafter also referred to as "SHG element"), and the outgoing surface of the active layer of the semiconductor laser and the incident surface of the optical waveguide of the SHG element are directly coupled to submicron order Laser light sources that have been approached or in close proximity have been proposed.
　また、端面発光型の半導体レーザは、量産性を向上させるために、大判の基板（ウェハ）をダイシング及び劈開を用いて多数個に分割してレーザ共振器を形成することで、安価に提供されているものが多い。こうした半導体レーザでは、出射面を含む端面が、結晶方位の関係で傾斜した傾斜劈開面になっている。 In addition, an edge-emitting semiconductor laser is provided inexpensively by forming a laser resonator by dividing a large substrate (wafer) into a large number using dicing and cleaving in order to improve mass productivity. There are many things that In such a semiconductor laser, the end face including the emission face is an inclined cleavage plane which is inclined due to the crystal orientation.
　図８（ａ）は、傾斜劈開面を有する半導体レーザ２２を用いた従来のレーザ光源２０の断面図である。レーザ光源２０は、基板２１と、半導体レーザ２２と、ＳＨＧ素子２３とを有する。半導体レーザ２２とＳＨＧ素子２３は、放熱特性を改善するために基板２１上にフェースダウンで搭載され、半導体レーザ２２は金－錫半田で、ＳＨＧ素子２３は接着剤で固着されている。半導体レーザ２２の活性層２２１の出射面２２２と、ＳＨＧ素子２３の光導波路２３１の入射面２３２は、直接結合でミクロンオーダーまで接近している。半導体レーザ２２は、活性層２２１の出射面２２２から赤外レーザ光を出射し、そのレーザ光は、ＳＨＧ素子２３の光導波路２３１の入射面２３２に入射する。ＳＨＧ素子２３は、入射したレーザ光が光導波路２３１を伝搬する間にそのレーザ光を波長変換して、緑色光又は青紫色光として出射する。 FIG. 8A is a cross-sectional view of a conventional laser light source 20 using a semiconductor laser 22 having an inclined cleavage plane. The laser light source 20 includes a substrate 21, a semiconductor laser 22, and an SHG element 23. The semiconductor laser 22 and the SHG element 23 are mounted face-down on the substrate 21 to improve the heat dissipation characteristics, the semiconductor laser 22 is fixed by gold-tin solder, and the SHG element 23 is fixed by an adhesive. The exit surface 222 of the active layer 221 of the semiconductor laser 22 and the entrance surface 232 of the optical waveguide 231 of the SHG element 23 are in close proximity to each other on the micron order by direct coupling. The semiconductor laser 22 emits an infrared laser beam from the emission surface 222 of the active layer 221, and the laser beam enters the incident surface 232 of the optical waveguide 231 of the SHG element 23. The SHG element 23 converts the wavelength of the incident laser light while propagating the light through the optical waveguide 231 and emits the light as green light or blue-violet light.
　図８（ｂ）は、図８（ａ）における半導体レーザ２２とＳＨＧ素子２３とのバットカップリング（butt coupling）部分Ｃの拡大部分断面図である。レーザ光源２０では、光導波路２３１の入射面２３２を含むＳＨＧ素子２３の入射端面２３３は、ＳＨＧ素子２３の底面に垂直である。一方、半導体レーザ２２の傾斜劈開面２２３は、結晶方位の関係で、例えばＧａＡｓ系の半導体レーザの場合は底面に垂直な面に対して傾斜角度θ２＝√２°で、ＳＨＧ素子２３に向かって傾斜（オーバーハング）している。図８（ｂ）では、この状態を模式的に示している。 FIG. 8B is an enlarged partial cross-sectional view of a butt coupling portion C of the semiconductor laser 22 and the SHG element 23 in FIG. 8A. In the laser light source 20, the incident end face 233 of the SHG element 23 including the incident surface 232 of the optical waveguide 231 is perpendicular to the bottom surface of the SHG element 23. On the other hand, the inclined cleavage plane 223 of the semiconductor laser 22 is directed toward the SHG element 23 at an inclination angle θ2 = √2 ° with respect to a plane perpendicular to the bottom surface, for example, in the case of a GaAs semiconductor laser. It is inclined (overhanging). This state is schematically shown in FIG.
　また、特許文献１では、ＳＨＧ素子の入射面の一部を半導体レーザの出射面に対して傾斜させることにより、半導体レーザからＳＨＧ素子への放熱の影響を低減させたレーザ光源が提案されている。 Further, Patent Document 1 proposes a laser light source in which the influence of heat radiation from the semiconductor laser to the SHG element is reduced by inclining a part of the incident surface of the SHG element with respect to the emission surface of the semiconductor laser. .
　図９（ａ）は、特許文献１のレーザ光源３０の断面図である。また、図９（ｂ）は、図９（ａ）における半導体レーザ３２とＳＨＧ素子３３とのバットカップリング部分Ｄの拡大部分断面図である。 FIG. 9A is a cross-sectional view of the laser light source 30 of Patent Document 1. As shown in FIG. 9B is an enlarged partial cross-sectional view of butt coupling portion D of semiconductor laser 32 and SHG element 33 in FIG. 9A.
　レーザ光源３０は、図８（ａ）及び図８（ｂ）に示したレーザ光源２０と同様に、基板３１と、半導体レーザ３２と、ＳＨＧ素子３３とを有する。ただし、レーザ光源３０のＳＨＧ素子３３では、光導波路３３１の上に貼り合わされた基板３３０の端面３３３が、基板３１に垂直な面に対して角度θ１＝３０°～４５°で傾斜研磨されている。一方、光導波路３３１の入射面３３２と半導体レーザ３２の出射面３２２は、傾斜面ではなく基板３１に垂直であり、互いに平行に対向している。このため、レーザ光源３０では、半導体レーザ３２とＳＨＧ素子３３とを接近させて配置することができ、良好な結合効率が得られる。更に、レーザ光源３０では、半導体レーザ３２に対向するＳＨＧ素子３３の基板３３０の端面３３３が傾斜面であるから、半導体レーザ３２からの放射熱がＳＨＧ素子３３に伝達されにくく、ＳＨＧ素子３３の温度上昇が低減される。 The laser light source 30 has a substrate 31, a semiconductor laser 32, and an SHG element 33, as in the laser light source 20 shown in FIGS. 8A and 8B. However, in the SHG element 33 of the laser light source 30, the end face 333 of the substrate 330 bonded onto the optical waveguide 331 is slope-polished at an angle θ1 = 30 ° to 45 ° with respect to the plane perpendicular to the substrate 31. . On the other hand, the incident surface 332 of the optical waveguide 331 and the emission surface 322 of the semiconductor laser 32 are perpendicular to the substrate 31 instead of the inclined surface, and face each other in parallel. Therefore, in the laser light source 30, the semiconductor laser 32 and the SHG element 33 can be disposed close to each other, and good coupling efficiency can be obtained. Furthermore, in the laser light source 30, since the end face 333 of the substrate 330 of the SHG element 33 facing the semiconductor laser 32 is an inclined surface, the radiation heat from the semiconductor laser 32 is not easily transmitted to the SHG element 33, and the temperature of the SHG element 33 The rise is reduced.
特開２００３－２６２８９６号公報（図１、図５）Unexamined-Japanese-Patent No. 2003-262896 (FIG. 1, FIG. 5)
　図８（ａ）及び図８（ｂ）に示すレーザ光源２０では、半導体レーザ２２の傾斜劈開面２２３がＳＨＧ素子２３に向かって傾斜（オーバーハング）しているため、半導体レーザ２２の傾斜劈開面２２３の上部端２２４（活性層２２１とは反対側の端部）がＳＨＧ素子２３の入射端面２３３に突き当たる。したがって、レーザ光源２０では、半導体レーザ２２の出射面２２２とＳＨＧ素子２３の入射面２３２とをサブミクロンオーダーまで接近させることが不可能であり、結合効率が著しく損なわれる。 In the laser light source 20 shown in FIGS. 8A and 8B, since the inclined cleavage surface 223 of the semiconductor laser 22 is inclined (overhanged) toward the SHG element 23, the inclined cleavage surface of the semiconductor laser 22 is The upper end 224 (the end opposite to the active layer 221) of the HG 223 abuts on the incident end face 233 of the SHG element 23. Therefore, with the laser light source 20, it is impossible to bring the exit surface 222 of the semiconductor laser 22 and the incident surface 232 of the SHG element 23 close to sub-micron order, and the coupling efficiency is significantly impaired.
　これに対し、図９（ａ）及び図９（ｂ）に示すレーザ光源３０では、ＳＨＧ素子３３の基板３３０が角度θ１＝３０°～４５°で傾斜研磨されているので、半導体レーザ３２の端面が傾斜劈開面であっても、その上部端がＳＨＧ素子３３の入射端面３３３に突き当たることはない。したがって、特許文献１のレーザ光源３０では、半導体レーザ３２の出射面３２２とＳＨＧ素子３３の入射面３３２とをサブミクロンオーダーまで接近又は密接させることが可能である。 On the other hand, in the laser light source 30 shown in FIGS. 9A and 9B, since the substrate 330 of the SHG element 33 is slope-polished at an angle θ1 = 30 ° to 45 °, the end face of the semiconductor laser 32 Even if it is an inclined cleavage surface, the upper end thereof does not abut the incident end face 333 of the SHG element 33. Therefore, in the laser light source 30 of Patent Document 1, the emission surface 322 of the semiconductor laser 32 and the incident surface 332 of the SHG element 33 can be brought close to or in close contact with each other to a submicron order.
　しかしながら、特許文献１では、半導体レーザからの放射熱のＳＨＧ素子への影響を低減させるために傾斜角度が大きく形成されているのであって、半導体レーザ３２の傾斜劈開面に関しては一切言及されていない。 However, in Patent Document 1, the inclination angle is formed large in order to reduce the influence of the radiation heat from the semiconductor laser on the SHG element, and no mention is made of the inclined cleavage plane of the semiconductor laser 32. .
　しかも、ＳＨＧ素子３３を作製するには、θ１＝３０°～４５°の傾斜角度を有する基板３３０の尖った先端に、光導波路３３１を位置決めして貼り合わせる必要がある。このため、ＳＨＧ素子３３の製造工程は難易度が高く、工数が膨大になるので、量産が難しく、したがって特許文献１のレーザ光源３０は高価になる。 Moreover, in order to manufacture the SHG element 33, it is necessary to position and bond the optical waveguide 331 to the pointed end of the substrate 330 having an inclination angle of θ1 = 30 ° -45 °. For this reason, the manufacturing process of the SHG element 33 is high in difficulty and the number of steps is enormous, so that mass production is difficult, and hence the laser light source 30 of Patent Document 1 becomes expensive.
　更に、ＳＨＧ素子３３の基板３３０のバットカップリング部分には大きな角度θ１の傾斜面が形成されているから、塵埃等が結合部分の間隙に挟まりやすく、出射光の妨げになる。 Furthermore, since a butt coupling portion of the substrate 330 of the SHG element 33 is formed with an inclined surface with a large angle θ1, dust and the like are easily caught in the gap of the coupled portion, which interferes with the emitted light.
　そこで、本発明の目的は、傾斜劈開面を有する半導体レーザの活性層の出射面と光導波路型波長変換素子の光導波路の入射面とをバットカップリングさせてサブミクロンオーダーまで接近させることが可能なレーザ光源を提供することである。また、本発明の目的は、半導体レーザと光導波路型波長変換素子との結合効率を向上させた、高出力のレーザ光源を提供することである。 Therefore, it is an object of the present invention to allow butt-coupling between the exit surface of the active layer of a semiconductor laser having a tilted cleavage surface and the entrance surface of the optical waveguide of the optical waveguide type wavelength conversion element to approach submicron order. Providing a laser light source. Another object of the present invention is to provide a high-power laser light source in which the coupling efficiency between a semiconductor laser and an optical waveguide type wavelength conversion element is improved.
　レーザ光源は、基板と、半導体レーザと光導波路型波長変換素子とを有し、半導体レーザの活性層の出射面と光導波路型波長変換素子の光導波路の入射面が直接対向する位置となるように基板上に固定されたレーザ光源において、半導体レーザの出射面は、活性層を底面にしてオーバーハングとなるような傾斜角度を有する傾斜劈開面であり、光導波路型波長変換素子の入射面を有する入射端面が、半導体レーザの傾斜劈開面の傾斜角度に合わせて傾斜した形状をなしていることにより、半導体レーザの出射面を光導波路型波長変換素子の入射面に接近させることを特徴とする。 The laser light source has a substrate, a semiconductor laser and an optical waveguide type wavelength conversion element, and the emission surface of the active layer of the semiconductor laser and the incident surface of the optical waveguide of the optical waveguide type wavelength conversion element are directly opposed to each other. In the laser light source fixed on the substrate, the emission surface of the semiconductor laser is an inclined cleavage surface having an inclination angle which causes an overhang with the active layer on the bottom, and the incident surface of the optical waveguide type wavelength conversion element is The light emitting device according to the present invention is characterized in that the light emitting surface of the semiconductor laser is brought close to the light incident surface of the optical waveguide type wavelength conversion element by forming the incident end face having a shape inclined according to the inclination angle of the inclined cleavage surface of the semiconductor laser. .
　また、レーザ光源は、基板と、活性層を底面にして基板上に固定された半導体レーザと、光導波路の入射面が半導体レーザの活性層の出射面に直接対向するように基板上に固定された光導波路型波長変換素子とを有し、半導体レーザの出射面は傾斜劈開面であり、光導波路型波長変換素子は、光導波路の入射面を含めて半導体レーザの傾斜劈開面の傾斜角度に合わせて傾斜した入射端面を有することを特徴とする。 The laser light source is fixed on the substrate such that the substrate, the semiconductor laser fixed on the substrate with the active layer on the bottom, and the incident surface of the optical waveguide directly face the emission surface of the active layer of the semiconductor laser. The output surface of the semiconductor laser is a tilted cleavage plane, and the optical waveguide type wavelength conversion device includes the incident plane of the optical waveguide at the inclination angle of the inclined cleavage plane of the semiconductor laser. It is characterized by having a sloped incident end face together.
　上記のレーザ光源では、半導体レーザの出射面は、光導波路型波長変換素子に対してオーバーハングとなるように傾斜した傾斜劈開面であることが好ましい。 In the above-described laser light source, it is preferable that the emission surface of the semiconductor laser be an inclined cleavage surface which is inclined so as to be an overhang with respect to the optical waveguide type wavelength conversion element.
　上記のレーザ光源では、光導波路型波長変換素子の入射端面は、基板に垂直な面に対して、半導体レーザの傾斜劈開面より大きい傾斜角度を有することが好ましい。 In the above laser light source, it is preferable that the incident end face of the optical waveguide type wavelength conversion element has an inclination angle larger than the inclined cleavage surface of the semiconductor laser with respect to the plane perpendicular to the substrate.
　上記のレーザ光源では、光導波路型波長変換素子の入射端面は、基板に垂直な面に対して３°以内の傾斜角度を有することが好ましい。 In the above laser light source, the incident end face of the optical waveguide type wavelength conversion element preferably has an inclination angle of 3 ° or less with respect to a plane perpendicular to the substrate.
　上記のレーザ光源では、光導波路型波長変換素子の入射端面は、光導波路の入射面を含む１つの平面であることが好ましい。 In the above laser light source, the incident end face of the optical waveguide type wavelength conversion element is preferably one plane including the incident surface of the optical waveguide.
　上記のレーザ光源では、半導体レーザと光導波路型波長変換素子は、Ａｕからなるマイクロバンプ構造を有する接合部を介して、基板との間で表面活性化接合技術により接合されていることが好ましい。 In the above laser light source, it is preferable that the semiconductor laser and the optical waveguide type wavelength conversion element be bonded to the substrate by a surface activation bonding technique through a bonding portion having a micro bump structure made of Au.
　上記のレーザ光源によれば、傾斜劈開面を有する半導体レーザの活性層の出射面と光導波路型波長変換素子の光導波路の入射面とをバットカップリングさせてサブミクロンオーダーまで接近させることが可能となる。更に、上記のレーザ光源によれば、半導体レーザと光導波路型波長変換素子との結合効率が向上して、高出力が得られる。 According to the above laser light source, it is possible to butt-couple the emission surface of the active layer of the semiconductor laser having the inclined cleavage plane and the incident surface of the optical waveguide of the optical waveguide type wavelength conversion element to approach submicron order. It becomes. Furthermore, according to the above laser light source, the coupling efficiency between the semiconductor laser and the optical waveguide type wavelength conversion element is improved, and high output can be obtained.
レーザ光源１の斜視図である。FIG. 2 is a perspective view of a laser light source 1; レーザ光源１の図１におけるＡ－Ａ断面図及びバットカップリング部分Ｂの拡大部分断面図である。FIG. 2 is a cross-sectional view of the laser light source 1 taken along line AA in FIG. 1 and an enlarged partial cross-sectional view of a butt coupling portion B. FIG. 半導体レーザ１２の断面図である。FIG. 2 is a cross-sectional view of a semiconductor laser 12; 半導体レーザ１２をレーザ光源１とは逆向きに搭載したレーザ光源１’のバットカップリング部分の拡大部分断面図である。FIG. 5 is an enlarged partial cross-sectional view of a butt coupling portion of a laser light source 1 ′ in which the semiconductor laser 12 is mounted in a direction opposite to that of the laser light source 1. レーザ光源１のＳＨＧ素子１３の製造工程を説明するための工程図である。FIG. 7 is a process diagram for describing a manufacturing process of the SHG element 13 of the laser light source 1; 図５に続くＳＨＧ素子１３の製造工程を説明するための工程図である。FIG. 6 is a process diagram for describing a manufacturing process of the SHG element 13 following FIG. 5. レーザ光源２，２’のバットカップリング部分の拡大部分断面図である。It is an expanded fragmentary sectional view of the butt coupling part of laser light source 2, 2 '. 傾斜劈開面を有する半導体レーザ２２を用いた従来のレーザ光源２０の断面図及びバットカップリング部分Ｃの拡大部分断面図である。It is sectional drawing of the conventional laser light source 20 using the semiconductor laser 22 which has an inclined cleavage plane, and an enlarged fragmentary sectional view of butt coupling part C. FIG. 特許文献１のレーザ光源３０の断面図及びバットカップリング部分Ｄの拡大部分断面図である。It is sectional drawing of the laser light source 30 of patent document 1, and an expanded fragmentary sectional view of butt coupling part D. FIG.
　以下、図面を参照して、レーザ光源について説明する。なお、以下では、いわゆる赤外光を発光する半導体レーザと、そのレーザ光を１／２波長の二次高調波である緑色光に変換するＳＨＧ素子とを基板上でフェースダウン実装して、半導体レーザの活性層の出射面とＳＨＧ素子の光導波路の入射面とを直接結合させる例について説明する。 The laser light source will be described below with reference to the drawings. In the following, a semiconductor laser for emitting so-called infrared light and an SHG element for converting the laser light into green light, which is a second harmonic of half wavelength, are mounted facedown on a substrate to form a semiconductor An example in which the emission surface of the active layer of the laser and the incident surface of the optical waveguide of the SHG element are directly coupled will be described.
　図１は、レーザ光源１の斜視図である。図２（ａ）は、レーザ光源１の図１におけるＡ－Ａ断面図である。また、図２（ｂ）は、図２（ａ）における半導体レーザ１２とＳＨＧ素子１３とのバットカップリング部分Ｂの拡大部分断面図である。 FIG. 1 is a perspective view of a laser light source 1. FIG. 2A is a cross-sectional view of the laser light source 1 taken along the line AA in FIG. 2B is an enlarged partial cross-sectional view of butt coupling portion B of semiconductor laser 12 and SHG element 13 in FIG. 2A.
　図１に示すように、レーザ光源１は、Ｓｉプラットフォーム１１と、半導体レーザ１２と、ＳＨＧ素子１３とを有する。Ｓｉプラットフォーム１１は、配線パターン、ランド、ロジックＬＳＩ、温度センサ、並びに光配線及び光回路となる光導波路等が形成されたシリコン基板である。半導体レーザ１２は、例えばＧａＡｓ、ＧａＮ等の材質からなり、近赤外用のＧａＡｓレーザを用いる場合には、活性層１２１の出射面から波長１０６４ｎｍの赤外レーザ光を出射する。ＳＨＧ素子１３は、例えばニオブ酸リチウム（ＬｉＮｂＯ３）からなるＬＮ基板１３０と、酸化マグネシウムをドープしたニオブ酸リチウム（ＭｇＯ－ＬｉＮｂＯ３）からなる光導波路基板１３１とが接合されて形成される。ＳＨＧ素子１３は、光導波路基板１３１の光導波路の入射面に入射した赤外レーザ光を高調波に変換して、波長５３２ｎｍの緑色レーザ光Ｇを出射する。 As shown in FIG. 1, the laser light source 1 has a Si platform 11, a semiconductor laser 12, and an SHG element 13. The Si platform 11 is a silicon substrate on which a wiring pattern, a land, a logic LSI, a temperature sensor, an optical wiring, an optical waveguide to be an optical circuit, and the like are formed. The semiconductor laser 12 is made of, for example, a material such as GaAs or GaN, and when using a near-infrared GaAs laser, emits infrared laser light with a wavelength of 1064 nm from the emission surface of the active layer 121. SHG element 13, for example, a LN substrate 130 made of lithium niobate (LiNbO 3), and the optical waveguide substrate 131 made of lithium niobate doped with magnesium oxide (MgO-LiNbO 3) is formed are joined. The SHG element 13 converts the infrared laser light incident on the incident surface of the optical waveguide of the optical waveguide substrate 131 into a harmonic and emits green laser light G having a wavelength of 532 nm.
　図２（ａ）に示すように、半導体レーザ１２は、活性層１２１を下側にして、いわゆるフェースダウンでＳｉプラットフォーム１１の上面に搭載され、金－錫半田により固定されている。また、ＳＨＧ素子１３は、光導波路基板１３１の面を下側にして、同様にフェースダウンでＳｉプラットフォーム１１の上面に搭載され、調芯後、接着又は金－錫半田実装されている。レーザ光源１では、半導体レーザ１２の約２×２μｍ寸法の出射面とＳＨＧ素子１３の約４×４μｍ寸法の入射面とをバットカップリングで対向させ、更に、その間隔を１μｍ以下のサブミクロンオーダーの距離まで接近させる。レーザ光源１では、このような高精度の位置決めによって結合効率を向上させて、高出力が得られるようにしている。 As shown in FIG. 2A, the semiconductor laser 12 is mounted on the upper surface of the Si platform 11 so-called face-down with the active layer 121 down, and fixed by gold-tin solder. The SHG element 13 is also mounted face down on the top surface of the Si platform 11 with the surface of the optical waveguide substrate 131 facing down, and after alignment, it is bonded or gold-tin solder mounted. In the laser light source 1, the emission surface of the semiconductor laser 12 of about 2 × 2 μm and the incident surface of the SHG element 13 of about 4 × 4 μm are opposed by butt coupling, and the distance is less than 1 μm. Close to the distance of In the laser light source 1, the coupling efficiency is improved by such high-precision positioning, so that high output can be obtained.
　図２（ｂ）に示すように、半導体レーザ１２とＳＨＧ素子１３とのバットカップリング部分Ｂにおいて、半導体レーザ１２の活性層１２１は、レーザ光を出射する出射面１２２を有する。半導体レーザ１２の出射面１２２は、結晶方位の関係でＳｉプラットフォーム１１に垂直な面に対して角度θ２で傾斜した傾斜劈開面１２３と同一平面である。特に、レーザ光源１では、傾斜劈開面１２３は、上部端１２４（活性層１２１とは反対側の端部）がＳＨＧ素子１３に向かうように傾斜している。すなわち、傾斜劈開面１２３は、ＳＨＧ素子１３に対してオーバーハングとなるように傾斜している。以下では、傾斜劈開面１２３の傾斜角度θ２のことを、「劈開傾斜角度θ２」という。 As shown in FIG. 2B, in the butt coupling portion B of the semiconductor laser 12 and the SHG element 13, the active layer 121 of the semiconductor laser 12 has an emission surface 122 for emitting laser light. The emitting surface 122 of the semiconductor laser 12 is in the same plane as the inclined cleavage surface 123 inclined at an angle θ2 with respect to the plane perpendicular to the Si platform 11 due to the crystal orientation. In particular, in the laser light source 1, the inclined cleavage surface 123 is inclined such that the upper end 124 (the end opposite to the active layer 121) faces the SHG element 13. That is, the inclined cleavage plane 123 is inclined so as to be an overhang with respect to the SHG element 13. Hereinafter, the inclination angle θ2 of the inclined cleavage surface 123 is referred to as “cleavage inclination angle θ2”.
　ＳＨＧ素子１３の光導波路１３２は、半導体レーザ１２の出射面１２２に対向する入射面１３３を有する。以下では、半導体レーザ１２に面した、ＬＮ基板１３０と光導波路基板１３１（光導波路１３２）の端面のことを、ＳＨＧ素子１３の入射端面１３４という。入射端面１３４は、図９（ａ）及び図９（ｂ）のレーザ光源３０とは異なり、光導波路１３２の入射面１３３を含む１つの平面である。また、入射端面１３４は、半導体レーザ１２の傾斜劈開面１２３に合わせて、劈開傾斜角度θ２より僅かに大きな傾斜角度θ３で、上部端が半導体レーザ１２から離れるように傾斜している。 The optical waveguide 132 of the SHG element 13 has an incident surface 133 facing the output surface 122 of the semiconductor laser 12. Hereinafter, the end surfaces of the LN substrate 130 and the optical waveguide substrate 131 (optical waveguide 132) facing the semiconductor laser 12 will be referred to as the incident end surface 134 of the SHG element 13. The incident end face 134 is one plane including the incident surface 133 of the optical waveguide 132 unlike the laser light source 30 of FIGS. 9A and 9B. Further, the incident end face 134 is inclined so that the upper end thereof is separated from the semiconductor laser 12 at an inclination angle θ3 slightly larger than the cleavage inclination angle θ2 in accordance with the inclined cleavage surface 123 of the semiconductor laser 12.
　したがって、レーザ光源１では、半導体レーザ１２の劈開傾斜角度θ２に多少のバラツキがあったとしても、また、傾斜劈開面１２３に部分的な突起部があったとしても、半導体レーザ１２の傾斜劈開面１２３の上部端１２４がＳＨＧ素子１３の入射端面１３４に突き当たることがない。このため、レーザ光源１では、半導体レーザ１２の出射面１２２とＳＨＧ素子１３の入射面１３３とをバットカップリングでサブミクロンオーダーまで接近させることが可能であり、高い結合効率が得られる。 Therefore, in the laser light source 1, even if the cleavage inclination angle θ 2 of the semiconductor laser 12 has some variations, and even if there are partial projections on the inclined cleavage surface 123, the inclined cleavage surface of the semiconductor laser 12 The upper end 124 of 123 does not abut the incident end surface 134 of the SHG element 13. Therefore, in the laser light source 1, it is possible to make the emission surface 122 of the semiconductor laser 12 and the incident surface 133 of the SHG element 13 approach each other to the submicron order by butt coupling, and high coupling efficiency can be obtained.
　半導体レーザ１２とＳＨＧ素子１３の結合効率ηと、Ｓｉプラットフォーム１１に垂直な面に対するＳＨＧ素子１３の入射端面１３４の傾斜角度θ３との関係は、傾斜角度θ３＝０°のときを結合効率η＝１００％とすると、傾斜角度θ３＝１°のとき結合効率η＝９８％であり、傾斜角度θ３＝２°のとき結合効率η＝９４％であり、傾斜角度θ３＝３°のとき結合効率η＝８６％である。 The relationship between the coupling efficiency η of the semiconductor laser 12 and the SHG element 13 and the inclination angle θ3 of the incident end surface 134 of the SHG element 13 with respect to the plane perpendicular to the Si platform 11 is the coupling efficiency == when the inclination angle θ3 = 0 °. Assuming that 100%, the coupling efficiency η = 98% when the inclination angle θ3 = 1 °, the coupling efficiency η = 94% when the inclination angle θ3 = 2 °, and the coupling efficiency 効率 when the inclination angle θ3 = 3 ° = 86%.
　したがって、入射端面１３４の傾斜角度θ３が３°以内であれば、結合効率ηは、傾斜角度θ３が０°（垂直面）のときの８６％程度まで減少するだけで済む。ただし、入射端面１３４の傾斜角度θ３が半導体レーザ１２の劈開傾斜角度θ２よりも小さいと、図８（ｂ）に示したように、半導体レーザ１２の傾斜劈開面１２３の上部端１２４がＳＨＧ素子２３の入射端面１３４に突き当たってしまう。したがって、ＳＨＧ素子１３の入射端面１３４の傾斜角度θ３は、半導体レーザ１２の劈開傾斜角度θ２よりも大きく、且つ３°以内であることが好ましい。例えば、半導体レーザ１２の劈開傾斜角度θ２が√２°である場合には、ＳＨＧ素子１３の入射端面１３４の傾斜角度θ３は、√２°より大きく、且つ３°以下であることが好ましい。 Therefore, if the inclination angle θ3 of the incident end face 134 is 3 ° or less, the coupling efficiency は only needs to be reduced to about 86% of that when the inclination angle θ3 is 0 ° (perpendicular surface). However, if the inclination angle θ3 of the incident end surface 134 is smaller than the cleavage inclination angle θ2 of the semiconductor laser 12, as shown in FIG. 8B, the upper end 124 of the inclined cleavage surface 123 of the semiconductor laser 12 is SHG element 23 But it strikes the incident end face 134 of the Therefore, the inclination angle θ3 of the incident end surface 134 of the SHG element 13 is preferably larger than the cleavage inclination angle θ2 of the semiconductor laser 12 and within 3 °. For example, when the cleavage inclination angle θ2 of the semiconductor laser 12 is √2 °, the inclination angle θ3 of the incident end surface 134 of the SHG element 13 is preferably larger than 大 き く 2 ° and 3 ° or less.
　なお、半導体レーザ１２の出射面１２２は、上部端がＳＨＧ素子１３から離れるように傾斜した傾斜劈開面であってもよい。この場合のレーザ光源について、図３と図４を用いて説明する。 The emission surface 122 of the semiconductor laser 12 may be an inclined cleavage surface in which the upper end is inclined away from the SHG element 13. The laser light source in this case will be described with reference to FIGS. 3 and 4.
　図３は、半導体レーザ１２の断面図である。上記のレーザ光源１における半導体レーザ１２は、図３の右側にある傾斜劈開面１２３を出射面１２２として使用している。しかしながら、半導体レーザ１２の出射面としては、傾斜劈開面１２３に限らず、傾斜劈開面１２３の反対側にある傾斜劈開面１２３’も同様に使用可能である。傾斜劈開面１２３と１２３’は、どちらも、結晶方位により定まる同じ大きさの劈開傾斜角度θ２で、半導体レーザ１２の底面に垂直な面に対して傾斜している。 FIG. 3 is a cross-sectional view of the semiconductor laser 12. The semiconductor laser 12 in the above-described laser light source 1 uses the inclined cleavage plane 123 located on the right side of FIG. However, the emitting surface of the semiconductor laser 12 is not limited to the inclined cleavage surface 123, and the inclined cleavage surface 123 ′ on the opposite side of the inclined cleavage surface 123 can be used similarly. The inclined cleavage surfaces 123 and 123 'are both inclined with respect to a plane perpendicular to the bottom surface of the semiconductor laser 12 at a cleavage inclination angle θ2 of the same size determined by the crystal orientation.
　図４は、半導体レーザ１２をレーザ光源１とは逆向きに搭載したレーザ光源１’のバットカップリング部分の拡大部分断面図である。レーザ光源１’は、半導体レーザ１２を搭載する向きと、ＳＨＧ素子１３の入射端面の傾斜角度のみがレーザ光源１と異なり、他の構成は全てレーザ光源１と同一である。このため、重複する構成部材の説明は省略する。 FIG. 4 is an enlarged partial cross-sectional view of a butt coupling portion of a laser light source 1 ′ in which the semiconductor laser 12 is mounted in the opposite direction to the laser light source 1. The laser light source 1 ′ differs from the laser light source 1 only in the mounting direction of the semiconductor laser 12 and the inclination angle of the incident end face of the SHG element 13, and all other configurations are the same as the laser light source 1. For this reason, the description of the overlapping structural members is omitted.
　レーザ光源１’では、半導体レーザ１２の活性層１２１の出射面１２２’は、上部端１２４’（活性層１２１とは反対側の端部）がＳＨＧ素子１３から離れるように傾斜した傾斜劈開面１２３’と同一平面である。また、レーザ光源１’のＳＨＧ素子１３では、光導波路１３２の入射面１３３’を含む入射端面１３４’がＳｉプラットフォーム１１に垂直な面になっている（すなわち、θ３＝０°である）。 In the laser light source 1 ′, the inclined cleavage surface 123 is inclined such that the upper end 124 ′ (the end opposite to the active layer 121) of the emission surface 122 ′ of the active layer 121 of the semiconductor laser 12 is separated from the SHG element 13. It is the same plane as'. Further, in the SHG element 13 of the laser light source 1 ′, the incident end face 134 ′ including the incident surface 133 ′ of the optical waveguide 132 is a plane perpendicular to the Si platform 11 (that is, θ3 = 0 °).
　これにより、レーザ光源１’でも、半導体レーザ１２の劈開傾斜角度θ２に多少のバラツキがあったとしても、また、傾斜劈開面１２３’に部分的な突起部があったとしても、半導体レーザ１２の傾斜劈開面１２３’の上部端１２４’がＳＨＧ素子１３の入射端面１３４’に突き当たることがない。このため、レーザ光源１’でも、半導体レーザ１２の出射面１２２’とＳＨＧ素子１３の入射面１３３’とをバットカップリングでサブミクロンオーダーまで接近させることが可能であり、高い結合効率が得られる。 As a result, even with the laser light source 1 ′, even if the cleavage inclination angle θ2 of the semiconductor laser 12 has some variations, and even if there are partial projections on the inclined cleavage surface 123 ′, The upper end 124 ′ of the inclined cleavage surface 123 ′ does not abut the incident end surface 134 ′ of the SHG element 13. Therefore, even with the laser light source 1 ′, the exit surface 122 ′ of the semiconductor laser 12 and the incident surface 133 ′ of the SHG element 13 can be close to submicron order by butt coupling, and high coupling efficiency can be obtained. .
　なお、ＳＨＧ素子１３の入射端面１３４’は、半導体レーザ１２の傾斜劈開面１２３’に合わせて、劈開傾斜角度θ２より僅かに大きな傾斜角度θ３で、上部端が半導体レーザ１２に向かうように傾斜していてもよい。あるいは、レーザ光源１’でも、入射端面１３４’は、レーザ光源１のＳＨＧ素子１３の入射端面１３４と同様に、傾斜角度θ３で上部端が半導体レーザ１２から離れるように傾斜していてもよい。ただし、半導体レーザ１２の出射面１２２’とＳＨＧ素子１３の入射端面１３４’とのなす角度が大きすぎると結合効率が悪くなるため、レーザ光源１と同様に、入射端面１３４’の傾斜角度θ３は３°以内であることが好ましい。この場合、劈開傾斜角度θ２と入射端面１３４’の傾斜角度θ３の向きを考慮すると、θ２＝√２°の場合には、半導体レーザ１２の出射面１２２’とＳＨＧ素子１３の入射端面１３４’とのなす角度は、√２°より大きく且つ３°＋√２°以内であることが好ましい。 The incident end face 134 'of the SHG element 13 is inclined such that the upper end is directed to the semiconductor laser 12 at an inclination angle θ3 slightly larger than the cleavage inclination angle θ2 in accordance with the inclined cleavage surface 123' of the semiconductor laser 12. It may be Alternatively, also in the laser light source 1 ′, the incident end face 134 ′ may be inclined so that the upper end is separated from the semiconductor laser 12 at the inclination angle θ 3 as in the incident end face 134 of the SHG element 13 of the laser light source 1. However, if the angle between the emitting surface 122 'of the semiconductor laser 12 and the incident end face 134' of the SHG element 13 is too large, the coupling efficiency is degraded. Therefore, as in the laser light source 1, the inclination angle θ3 of the incident end face 134 'is It is preferably within 3 °. In this case, considering the cleavage inclination angle θ2 and the direction of the inclination angle θ3 of the incident end surface 134 ′, the emission surface 122 ′ of the semiconductor laser 12 and the incident end surface 134 ′ of the SHG element 13 when θ2 = √2 °. Preferably, the angle formed by is greater than 22 ° and within 3 ° + √2 °.
　図５及び図６は、レーザ光源１のＳＨＧ素子１３の製造工程を説明するための工程図である。図５と図６を用いて、ＳＨＧ素子１３の入射端面１３４に傾斜角度θ３を形成する製造工程を説明する。なお、各図において同一の構成部材には同一の符号を付し、重複する説明は省略する。 5 and 6 are process diagrams for explaining the manufacturing process of the SHG element 13 of the laser light source 1. The manufacturing process for forming the inclination angle θ3 on the incident end surface 134 of the SHG element 13 will be described with reference to FIGS. 5 and 6. In each of the drawings, the same constituent members are denoted by the same reference numerals, and redundant description will be omitted.
　まず、図５に示すように、製造工程ＳＴ０１の貼合せ工程において、ニオブ酸リチウム（ＬｉＮｂＯ３）からなる大判ＬＮ基板１３０Ａと、分極反転用の共通電極を形成し酸化マグネシウムをドープしたニオブ酸リチウム（ＭｇＯ－ＬｉＮｂＯ３）からなる大判光導波路用基板１３１Ａとを、例えばエポキシ系接着剤で貼り合わせて、大判ＳＨＧ基板１３Ａを形成する。 First, as shown in FIG. 5, in the bonding step of the manufacturing step ST01, a large LN substrate 130A made of lithium niobate (LiNbO 3 ) and a common electrode for polarization inversion and lithium niobate doped with magnesium oxide are formed. The large-size optical waveguide substrate 131A made of (MgO-LiNbO 3 ) is bonded, for example, with an epoxy adhesive to form a large-size SHG substrate 13A.
　次に、製造工程ＳＴ０２の研磨工程において、大判光導波路用基板１３１Ａに対して粗研磨と仕上げ研磨とＣＭＰ（Chemical Mechanical Polishing）研磨を行って、厚さを４～５μｍほどにし、研磨面を鏡面に仕上げて、大判光導波路用研磨基板１３１Ｂを形成する。これにより、大判ＳＨＧ基板１３Ａは、極めて薄い大判光導波路用研磨基板１３１Ｂが０．５ｍｍ程度の厚さの大判ＬＮ基板１３０Ａに貼り付けられたものになる。 Next, in the polishing process of manufacturing process ST02, the large-size optical waveguide substrate 131A is subjected to rough polishing, final polishing, and CMP (Chemical Mechanical Polishing) polishing to a thickness of about 4 to 5 μm, and the polished surface is a mirror surface To form a large-sized optical waveguide polishing substrate 131B. As a result, the large-size SHG substrate 13A is obtained by bonding the very thin large-size optical waveguide polishing substrate 131B to the large-size LN substrate 130A having a thickness of about 0.5 mm.
　次に、製造工程ＳＴ０３の光導波路形成工程において、製造工程ＳＴ０２で得られた大判光導波路用研磨基板１３１Ｂに櫛歯電極を形成した後、分極反転処理を行い、更に、ドライエッチング又はレーザ加工を行って、多数本の不図示の光導波路が形成された大判光導波路形成基板１３１Ｃを形成する。 Next, in the optical waveguide forming step ST03 of the manufacturing step ST03, a comb electrode is formed on the large-size optical waveguide polishing substrate 131B obtained in the manufacturing step ST02, polarization inversion processing is performed, and dry etching or laser processing is further performed. Then, a large-size optical waveguide forming substrate 131C on which a large number of optical waveguides (not shown) are formed is formed.
　次に、製造工程ＳＴ０４のダイシング工程において、大判ＬＮ基板１３０Ａと光導波路が形成された大判光導波路形成基板１３１Ｃとを有する大判ＳＨＧ基板１３Ａに対し、図５に示すように、光導波路に平行な方向のダイシングラインＬ１及び光導波路に垂直な方向のダイシングラインＬ２に沿ってダイシングを行う。これにより、多数個のＳＨＧ子基板１３Ｂを形成する。個々のＳＨＧ子基板１３Ｂは、ＳＨＧ素子の集合体である。 Next, as shown in FIG. 5, the large-size SHG substrate 13A having the large-size LN substrate 130A and the large-size optical waveguide forming substrate 131C on which the optical waveguide is formed in the dicing step of the manufacturing process ST04 is parallel to the optical waveguide. Dicing is performed along dicing lines L1 in the direction and dicing lines L2 in the direction perpendicular to the optical waveguide. Thereby, a large number of SHG child substrates 13B are formed. Each SHG child substrate 13B is an assembly of SHG elements.
　続いて、図６に示す製造工程ＳＴ０５のセット工程において、製造工程ＳＴ０４でダイシングされたＳＨＧ子基板１３Ｂをピックアップして、研磨治具にセットする。ＳＨＧ子基板１３Ｂは、ニオブ酸リチウム（ＬｉＮｂＯ３）からなるＬＮ子基板１３０Ｂと、光導波路１３２が形成された光導波路子基板１３１Ｄとを有する。 Subsequently, in the setting step of the manufacturing process ST05 shown in FIG. 6, the SHG child substrate 13B diced in the manufacturing process ST04 is picked up and set in a polishing jig. The SHG child substrate 13B has an LN child substrate 130B made of lithium niobate (LiNbO 3 ), and an optical waveguide child substrate 131D in which the optical waveguide 132 is formed.
　次に、製造工程ＳＴ０６の端面研磨工程において、製造工程ＳＴ０５で示したＳＨＧ子基板１３Ｂの光導波路１３２の両端を研磨して、ＬＮ子基板１３０Ｃと、光導波路１３２の入射面１３３及び不図示の出射面を有する光導波路子基板１３１Ｅとを形成する。すなわち、ＳＨＧ子基板１３Ｂの光導波路の両端に対して粗研磨と仕上げ研磨とＣＭＰ（Chemical Mechanical Polishing）研磨を行って、ＳＨＧ子基板１３Ｂの入射端面１３４及び不図示の出射端面を光学的な鏡面に仕上げる。入射端面１３４は、光導波路１３２の入射面１３３を含む１つの平面に形成され、傾斜研磨によって、図２（ｂ）に示すように鉛直方向に対する傾斜角度θ３を有する。一方、不図示の出射面を含む出射端面は、垂直研磨されて、光導波路子基板１３１Ｅの底面に対し垂直になる。また、入射端面１３４及び出射端面には、光学的な処理として反射防止膜を成膜する。 Next, in the end face polishing process of the manufacturing process ST06, both ends of the optical waveguide 132 of the SHG child substrate 13B shown in the manufacturing process ST05 are polished to form the LN child substrate 130C, the incident surface 133 of the optical waveguide 132, and not shown. An optical waveguide substrate 131E having an exit surface is formed. That is, rough polishing, finish polishing, and CMP (Chemical Mechanical Polishing) polishing are performed on both ends of the optical waveguide of the SHG child substrate 13B to optically mirror the incident end face 134 and the emission end face (not shown) of the SHG child substrate 13B. Finish. The incident end surface 134 is formed in one plane including the incident surface 133 of the optical waveguide 132, and has an inclination angle θ3 with respect to the vertical direction as shown in FIG. 2B by inclined polishing. On the other hand, the emission end surface including the emission surface (not shown) is vertically polished and becomes perpendicular to the bottom surface of the optical waveguide substrate 131E. Further, an antireflection film is formed on the incident end surface 134 and the output end surface as an optical process.
　なお、端面研磨工程では、複数のＳＨＧ子基板１３Ｂを重ねた後に傾斜研磨を行ってもよい。ただし、個片化後のＳＨＧ素子１３の長さを揃えるためには、出射端面を垂直研磨する前に、傾斜研磨によって生じる長さの差を考慮して、各ＳＨＧ子基板１３Ｂを互いにずらしておく必要がある。 In the end face polishing process, inclined polishing may be performed after stacking a plurality of SHG daughter boards 13B. However, in order to make the lengths of the SHG elements 13 after singulation equal, the SHG child substrates 13B are mutually offset from each other in consideration of the length difference caused by the inclined polishing before the emission end face is vertically polished. You need to
　次に、製造工程ＳＴ０７のダイシング工程において、図６に示すように、ダイシングラインＬ３に沿ってダイシングを行い、ＳＨＧ素子の集合体であるＳＨＧ子基板１３Ｂを複数個のＳＨＧ素子１３に分離する。なお、カッティングラインＬ３は、ＳＨＧ素子１３の光導波路が中央部に沿って配置されるように形成される。 Next, in a dicing process of manufacturing process ST07, as shown in FIG. 6, dicing is performed along dicing line L3 to separate SHG child substrate 13B, which is an assembly of SHG elements, into a plurality of SHG elements 13. The cutting line L3 is formed such that the optical waveguide of the SHG element 13 is disposed along the central portion.
　次に、製造工程ＳＴ０８において、図６に示すように、分離されたＳＨＧ素子１３が得られる。 Next, in the manufacturing process ST08, as shown in FIG. 6, the separated SHG element 13 is obtained.
　以上の製造工程によって、ＬＮ基板１３０と光導波路基板１３１を有し、光導波路の入射側には入射面１３３を含む傾斜面である入射端面１３４が形成され、光導波路の出射側には不図示の出射面を含む垂直面である出射端面が形成されたＳＨＧ素子１３が得られる。入射端面１３４は、半導体レーザ１２の劈開傾斜角度θ２（例えば√２°）より大きく且つ３°以内である傾斜角度θ３を有する。 By the above manufacturing process, an incident end face 134 which is an inclined surface including the LN substrate 130 and the optical waveguide substrate 131 and which includes the incident surface 133 is formed on the incident side of the optical waveguide, and not shown on the emission side of the optical waveguide. The SHG element 13 in which the output end face which is a perpendicular | vertical surface containing the output surface of 4 is formed is obtained. The incident end face 134 has an inclination angle θ3 which is larger than the cleavage inclination angle θ2 (for example, √2 °) of the semiconductor laser 12 and is within 3 °.
　上記のように、半導体レーザ１２の出射面１２２に対向するＳＨＧ素子１３の入射面１３３と入射端面１３４とは、同一平面として同時に研磨加工できるため、ＳＨＧ素子１３の製造工程が単純化される。したがって、ＳＨＧ素子１３の製造が容易であり工数を短縮できるため、ＳＨＧ素子１３と、それを使用するレーザ光源１を安価に提供することが可能となる。 As described above, since the incident surface 133 and the incident end surface 134 of the SHG element 13 opposed to the emission surface 122 of the semiconductor laser 12 can be polished simultaneously as the same plane, the manufacturing process of the SHG element 13 is simplified. Therefore, since the manufacturing of the SHG element 13 is easy and the number of processes can be shortened, the SHG element 13 and the laser light source 1 using the same can be provided at low cost.
　そして、研磨による傾斜角度θ３は僅かな傾きであるから、バットカップリングの結合効率もほとんど低下することがなく、高出力のレーザ光源を提供することが可能となる。更に、劈開傾斜角度θ２に対し研磨による傾斜角度θ３の開きが小さいから、半導体レーザ１２の出射面１２２とＳＨＧ素子１３の入射面１３３との間に塵埃等が入ることはほとんどない。 Further, since the inclination angle θ3 by polishing is a slight inclination, the coupling efficiency of the butt coupling is hardly reduced, and it is possible to provide a high output laser light source. Furthermore, since the opening of the inclination angle θ3 by polishing is smaller than the cleavage inclination angle θ2, dust and the like hardly enter between the emission surface 122 of the semiconductor laser 12 and the incident surface 133 of the SHG element 13.
　図７（ａ）及び図７（ｂ）は、それぞれ、レーザ光源２，２’のバットカップリング部分の拡大部分断面図である。レーザ光源２，２’は、それぞれ、Ｓｉプラットフォーム１１と半導体レーザ１２及びＳＨＧ素子１３との接合方法のみがレーザ光源１，１’と異なり、他の構成は全てレーザ光源１，１’と同一である。このため、重複する構成部材の説明は省略する。 FIGS. 7 (a) and 7 (b) are enlarged partial sectional views of butt coupling portions of the laser light sources 2 and 2 ', respectively. The laser light sources 2 and 2 'are different from the laser light sources 1 and 1' only in the bonding method of the Si platform 11 and the semiconductor laser 12 and the SHG element 13, respectively, and all other configurations are the same as the laser light sources 1 and 1 '. is there. For this reason, the description of the overlapping structural members is omitted.
　Ｓｉプラットフォーム１１の上面には、不図示のシリコン酸化膜が形成されている。このシリコン酸化膜は、絶縁膜として、半導体レーザ１２等の電気素子が電気的に接続されるランド部領域以外の配線パターン等を絶縁している。そして、図７（ａ）及び図７（ｂ）に示すように、Ｓｉプラットフォーム１１の上面には、半導体レーザ１２とＳＨＧ素子１３を接合する領域に、それぞれ、Ａｕからなる多数のマイクロバンプを有する接合部１４２，１４４が形成されている。マイクロバンプは、例えば直径φ５μｍ、高さ２μｍの円柱状であり、接合部１４２，１４４においてピッチ１０～２５μｍで形成されている。 A silicon oxide film (not shown) is formed on the upper surface of the Si platform 11. The silicon oxide film, as an insulating film, insulates wiring patterns and the like other than the land portion region to which the electric element such as the semiconductor laser 12 is electrically connected. Then, as shown in FIGS. 7A and 7B, the upper surface of the Si platform 11 has a large number of micro bumps made of Au in the region where the semiconductor laser 12 and the SHG element 13 are bonded. Junctions 142 and 144 are formed. The microbumps are, for example, cylindrical columns with a diameter of 5 μm and a height of 2 μm, and are formed with a pitch of 10 to 25 μm at the bonding portions 142 and 144.
　一方、半導体レーザ１２とＳＨＧ素子１３の下面、すなわち、Ｓｉプラットフォーム１１と接合される面には、それぞれ、Ａｕ膜１４１，１４３が成膜されている。そして、半導体レーザ１２は、Ａｕ膜１４１と接合部１４２のマイクロバンプとを表面活性化接合させることにより、Ｓｉプラットフォーム１１上に接合されている。同様に、ＳＨＧ素子１３は、Ａｕ膜１４３と接合部１４４のマイクロバンプとを表面活性化接合させることにより、Ｓｉプラットフォーム１１上に接合されている。ただし、光導波路の特性から、光導波路の近傍にＡｕ等の金属材が存在すると悪影響があるため、接合部１４４は、ＳＨＧ素子１３の下面全体でＡｕ膜１４３と接合するのではなく、少なくとも光導波路の幅の長手方向を除いた部分で接合している。 On the other hand, Au films 141 and 143 are formed on the lower surfaces of the semiconductor laser 12 and the SHG element 13, that is, the surfaces to be bonded to the Si platform 11. The semiconductor laser 12 is bonded onto the Si platform 11 by surface activation bonding of the Au film 141 and the micro bumps of the bonding portion 142. Similarly, the SHG element 13 is bonded onto the Si platform 11 by surface activation bonding of the Au film 143 and the micro bumps of the bonding portion 144. However, due to the characteristics of the optical waveguide, the presence of a metal material such as Au in the vicinity of the optical waveguide adversely affects the junction 144 not to be joined to the Au film 143 over the entire lower surface of the SHG element 13. It joins in the part except the longitudinal direction of the width | variety of a waveguide.
　表面活性化接合技術を利用するためには、まず、Ｓｉプラットフォーム１１と半導体レーザ１２とＳＨＧ素子１３に対して、６～８Ｐａレベルの真空下でアルゴンプラズマ処理を行う。これにより、半導体レーザ１２とＳＨＧ素子１３のＡｕ膜１４１，１４３及びＳｉプラットフォーム１１における接合部１４２，１４４のマイクロバンプの表面を覆っている酸化膜、コンタミ（塵）等の不活性層を取り除いて、それらの表面を活性化させる。 In order to use the surface activation bonding technology, first, argon plasma processing is performed on the Si platform 11, the semiconductor laser 12, and the SHG element 13 under a vacuum of 6 to 8 Pa level. As a result, the oxide films covering the surfaces of the micro bumps of the junction portions 142 and 144 of the semiconductor laser 12 and the Au films 141 and 143 of the SHG element 13 and the Si platform 11 are removed, and inactive layers such as contamination (dust) are removed. , Activate their surface.
　次に、図７（ａ）及び図７（ｂ）に示すように半導体レーザ１２とＳＨＧ素子１３をＳｉプラットフォーム１１に載置して、１５０℃以下の常温大気中で荷重（例えば、５～１０Ｋｇｆ／ｍｍ２）を掛けて加圧する。マイクロバンプは荷重に応じて厚み方向に僅かに潰れて変形し、Ａｕ原子の共有結合により、Ｓｉプラットフォーム１１と半導体レーザ１２及びＳＨＧ素子１３とが確実に接合される。 Next, as shown in FIGS. 7A and 7B, the semiconductor laser 12 and the SHG element 13 are mounted on the Si platform 11, and a load (for example, 5 to 10 Kgf) in a normal temperature atmosphere of 150.degree. Apply pressure by applying / mm 2 ). The microbumps are slightly crushed and deformed in the thickness direction according to the load, and the Si platform 11 and the semiconductor laser 12 and the SHG element 13 are securely bonded by covalent bonding of Au atoms.
　表面活性化接合技術によれば、加熱温度が常温レベルの１５０℃以下であるから、半導体レーザ１２、ＳＨＧ素子１３等の部品を接合したとしても、熱膨張係数差の残留応力による部品破壊、熱ストレスによる機能劣化、熱膨張による位置ズレ等の問題を生じることがない。このため、レーザ光源２では、半導体レーザ１２とＳＨＧ素子１３を同一の基板上にサブミクロンオーダーで高精度に実装できるから、半導体レーザ１２とＳＨＧ素子１３のバットカップリング部分での結合効率が向上し、高出力を得ることが可能となる。 According to the surface activation bonding technology, since the heating temperature is 150 ° C. or less at the normal temperature level, even if the parts such as the semiconductor laser 12 and the SHG element 13 are bonded, the parts are broken due to the residual stress of the thermal expansion coefficient difference There is no problem of functional deterioration due to stress or positional deviation due to thermal expansion. Therefore, in the laser light source 2, the semiconductor laser 12 and the SHG element 13 can be mounted on the same substrate with high precision on the same substrate, so the coupling efficiency at the butt coupling portion between the semiconductor laser 12 and the SHG element 13 is improved. And high output can be obtained.
　なお、本発明は、上述したレーザ光源１，１’，２，２’に限定されることはなく、それらの全ての構成を含む必要もなく、特許請求の範囲に記載した内容の範囲内で種々の変更又は省略を行ってもよいことは言うまでもない。 The present invention is not limited to the above-described laser light sources 1, 1 ', 2, 2', and it is not necessary to include all of the configurations thereof, within the scope of the contents described in the claims. It goes without saying that various changes or omissions may be made.
　１，１’，２，２’　　レーザ光源
　１１　　Ｓｉプラットフォーム
　１２　　半導体レーザ
　１３　　ＳＨＧ素子（光導波路型波長変換素子）
　１２１　　活性層
　１２２，１２２’　　出射面
　１２３，１２３’　　傾斜劈開面
　１２４，１２４’　　上部端
　１３０　　ＬＮ基板
　１３１　　光導波路基板
　１３２　　光導波路
　１３３，１３３’　　入射面
　１３４，１３４’　　入射端面
　１４１，１４３　　Ａｕ膜
　１４２，１４４　　接合部 1,1 ', 2,2' laser light source 11 Si platform 12 semiconductor laser 13 SHG element (optical waveguide type wavelength conversion element)
121 active layer 122, 122 'exit surface 123, 123' inclined cleavage plane 124, 124 'upper end 130 LN substrate 131 optical waveguide substrate 132 optical waveguide 133, 133' entrance surface 134, 134 ' entrance end surface 141, 143 Au film 142 , 144 joints

Claims (6)

  1. 　基板と、
    　活性層を底面にして前記基板上に固定された半導体レーザと、
    　光導波路の入射面が前記半導体レーザの活性層の出射面に直接対向するように前記基板上に固定された光導波路型波長変換素子と、を有し、
    　前記半導体レーザの出射面は傾斜劈開面であり、
    　前記光導波路型波長変換素子は、前記光導波路の入射面を含めて前記半導体レーザの傾斜劈開面の傾斜角度に合わせて傾斜した入射端面を有する、
    　ことを特徴とするレーザ光源。     A substrate,
    A semiconductor laser fixed on the substrate with the active layer on the bottom;
    An optical waveguide type wavelength conversion element fixed on the substrate such that the incident surface of the optical waveguide directly faces the emission surface of the active layer of the semiconductor laser,
    The emitting surface of the semiconductor laser is an inclined cleavage surface,
    The optical waveguide type wavelength conversion element has an incident end face that is inclined according to the inclination angle of the inclined cleavage surface of the semiconductor laser, including the incident surface of the optical waveguide.
    Laser light source characterized by
  2. 　前記半導体レーザの出射面は、前記光導波路型波長変換素子に対してオーバーハングとなるように傾斜した傾斜劈開面である、請求項１に記載のレーザ光源。 The laser light source according to claim 1, wherein the emission surface of the semiconductor laser is an inclined cleavage surface which is inclined to be an overhang with respect to the optical waveguide type wavelength conversion element.
  3. 　前記光導波路型波長変換素子の入射端面は、前記基板に垂直な面に対して、前記半導体レーザの傾斜劈開面より大きい傾斜角度を有する、請求項１又は２に記載のレーザ光源。 The laser light source according to claim 1 or 2, wherein the incident end face of the optical waveguide type wavelength conversion element has an inclination angle larger than the inclined cleavage surface of the semiconductor laser with respect to a plane perpendicular to the substrate.
  4. 　前記光導波路型波長変換素子の入射端面は、前記基板に垂直な面に対して３°以内の傾斜角度を有する、請求項１～３のいずれか一項に記載のレーザ光源。 The laser light source according to any one of claims 1 to 3, wherein an incident end face of the optical waveguide type wavelength conversion element has an inclination angle of 3 ° or less with respect to a plane perpendicular to the substrate.
  5. 　前記光導波路型波長変換素子の入射端面は、前記光導波路の入射面を含む１つの平面である、請求項１～４のいずれか一項に記載のレーザ光源。 The laser light source according to any one of claims 1 to 4, wherein an incident end face of the optical waveguide type wavelength conversion element is one plane including an incident surface of the optical waveguide.
  6. 　前記半導体レーザと前記光導波路型波長変換素子は、Ａｕからなるマイクロバンプ構造を有する接合部を介して、前記基板との間で表面活性化接合技術により接合されている、請求項１～５のいずれか一項に記載のレーザ光源。 6. The semiconductor laser according to claim 1, wherein said semiconductor laser and said optical waveguide type wavelength conversion element are bonded to said substrate by a surface activation bonding technique via a bonding portion having a micro bump structure made of Au. The laser light source according to any one of the preceding claims.
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