Classifications

• • 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
  • H01S5/11—Comprising a photonic bandgap structure
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
• • 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
  • H01S5/0233—Mounting configuration of laser chips
  • H01S5/0234—Up-side down mountings, e.g. Flip-chip, epi-side down mountings or junction down mountings
• • 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
  • H01S5/0239—Combinations of electrical or optical elements
• • 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
  • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
  • H01S5/042—Electrical excitation ; Circuits therefor
  • H01S5/0425—Electrodes, e.g. characterised by the structure
  • H01S5/04256—Electrodes, e.g. characterised by the structure characterised by the configuration
• • 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
  • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
  • H01S5/042—Electrical excitation ; Circuits therefor
  • H01S5/0425—Electrodes, e.g. characterised by the structure
  • H01S5/04256—Electrodes, e.g. characterised by the structure characterised by the configuration
  • H01S5/04257—Electrodes, e.g. characterised by the structure characterised by the configuration having positive and negative electrodes on the same side of the substrate
• • 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
  • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
  • H01S5/185—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL]
• • 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
  • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
  • H01S5/2004—Confining in the direction perpendicular to the layer structure
  • H01S5/2018—Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers
  • H01S5/2027—Reflecting region or layer, parallel to the active layer, e.g. to modify propagation of the mode in the laser or to influence transverse modes
• • 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
  • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
  • H01S5/42—Arrays of surface emitting lasers
• • 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
  • H01S2301/00—Functional characteristics
  • H01S2301/17—Semiconductor lasers comprising special layers
  • H01S2301/176—Specific passivation layers on surfaces other than the emission facet

Definitions

• the technology disclosed herein (hereinafter also referred to as "the technology”) relates to a light source device.
• Photonic crystal surface-emitting lasers that have a photonic crystal near the active layer are known.
• Photonic crystal surface-emitting lasers are devices that have the general advantages of semiconductor lasers such as small size and long life, such as vertical-cavity surface-emitting lasers (VCSELs), which have seen remarkable applications in recent years in industries such as distance measurement sensors and optical communications.
• VCSELs vertical-cavity surface-emitting lasers
• photonic crystal surface-emitting lasers have the advantage of having a photonic crystal structure, that is, they can emit light with a narrow divergence angle, an advantage not available with other surface-emitting lasers (e.g. VCSELs).
• Patent Document 1 proposes a projector (light source device) in which a PCSEL is electrically connected to a laser driver by wire bonding.
• Patent Document 2 proposes a light source device in which a VCSEL is electrically connected to a laser driver via a flip chip.
• the main objective of this technology is to provide a light source device that can narrow the spread angle of the emitted light while also achieving miniaturization and reduced inductance.
• the present technology provides a photonic crystal surface emitting laser having at least one light emitting element portion in which a plurality of layers including an active layer and a photonic crystal layer are stacked; a laser driver electrically connected to the photonic crystal surface emitting laser via a bump;
• the present invention provides a light source device comprising:
• the photonic crystal surface-emitting laser may have first and second electrodes on the laser driver side for passing electricity through the light-emitting element portion, the first electrode being electrically connected to the laser driver via a first bump, and the second electrode being electrically connected to the laser driver via a second bump.
• the photonic crystal surface-emitting laser may have a base portion aligned in an in-plane direction with the light-emitting element portion, the first electrode being provided on a surface of the light-emitting element portion facing the laser driver, and the second electrode being provided on a surface of the base portion facing the laser driver.
• the photonic crystal surface-emitting laser may have a substrate on which the light-emitting element portion and the pedestal portion are protruded, and a wiring connected to the second electrode and extending from the second electrode side along the pedestal portion toward the substrate side.
• the photonic crystal surface emitting laser may have an intermediate electrode that is directly or indirectly provided on the substrate and connected to the wiring.
• the photonic crystal surface emitting laser may include a low resistance layer having a lower resistance than the substrate, on the substrate side of the active layer and the photonic crystal layer.
• the substrate may be a semiconductor substrate, and the low resistance layer may be a tunnel junction layer.
• the low resistance layer may be a current spreading layer.
• the first and second electrodes may be provided on a surface of the light-emitting element portion facing the laser driver.
• the photonic crystal surface emitting laser may have a substrate on which the light emitting element portion is protruding, and a wiring connected to the second electrode and extending from the second electrode side along the light emitting element portion toward the substrate side.
• the photonic crystal surface emitting laser may have an intermediate electrode that is directly or indirectly provided on the substrate and connected to the wiring.
• the photonic crystal surface emitting laser may include a low resistance layer having a lower resistance than the substrate, on the substrate side of the active layer and the photonic crystal layer.
• the substrate may be a semiconductor substrate, and the low resistance layer may be a tunnel junction layer.
• the substrate may be a semi-insulating substrate or an insulating substrate, and the low resistance layer may be a current spreading layer.
• the laser driver may include a switching element connected to one of the first and second electrodes.
• the photonic crystal surface-emitting laser may have a plurality of the light-emitting element components arranged in an in-plane direction, the laser driver may have a plurality of switching elements corresponding to the plurality of light-emitting element components, and each of the plurality of switching elements may be connected to one of the first and second electrodes for passing current through a corresponding light-emitting element component.
• the photonic crystal surface emitting laser may include a current confinement layer.
• the photonic crystal surface emitting laser may include a reflecting mirror on the active layer and the photonic crystal layer opposite to an emission side of the photonic crystal surface emitting laser.
• the light emitting element portion may have a small diameter portion on the laser driver side or on the opposite side to the laser driver side.
• FIG. 1 is a cross-sectional view of a light source device according to a first example of an embodiment of the present technology.
• FIG. 2 is a schematic plan view of a light source device according to a first example of an embodiment of the present technology.
• FIG. 3 is a flowchart for explaining an example of a method for manufacturing the light source device of FIG. 4A to 4C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 5A to 5C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 6A to 6C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG.
• FIG. 7A to 7C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 8A to 8C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 9A to 9C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 10A to 10C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 11A to 11C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 12A to 12C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG.
• FIG. 13A to 13C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 14A to 14C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 15A to 15C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 16A to 16C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG. 17A to 17C are cross-sectional views illustrating steps in an example of a method for manufacturing the light source device of FIG.
• FIG. 18 is a cross-sectional view of a light source device according to Example 2 of an embodiment of the present technology.
• FIG. 19 is a cross-sectional view of a light source device according to Example 3 of an embodiment of the present technology.
• FIG. 20 is a cross-sectional view of a light source device according to Example 4 of an embodiment of the present technology.
• FIG. 21 is a cross-sectional view of a light source device according to Example 5 of an embodiment of the present technology.
• FIG. 22 is a schematic plan view of a light source device according to a fifth example of an embodiment of the present technology.
• FIG. 23 is a cross-sectional view of a light source device according to Example 6 of an embodiment of the present technology.
• FIG. 24 is a cross-sectional view of a light source device according to Example 7 of an embodiment of the present technology.
• FIG. 25 is a cross-sectional view of a light source device according to an eighth example of an embodiment of the present technology.
• FIG. 26 is a cross-sectional view of a light source device according to Example 9 of an embodiment of the present technology.
• FIG. 27 is a cross-sectional view of a light source device according to a tenth example of an embodiment of the present technology.
• FIG. 28 is a cross-sectional view of a light source device according to an eleventh example of an embodiment of the present technology.
• FIG. 29 is a cross-sectional view of a light source device according to Example 12 of an embodiment of the present technology.
• FIG. 30 is a cross-sectional view of a light source device according to Example 13 of an embodiment of the present technology.
• FIG. 31 is a cross-sectional view of a light source device according to Example 14 of an embodiment of the present technology.
• FIG. 32 is a diagram showing an example of application of the light source device of FIG. 1 to a distance measuring device.
• FIG. 33 is a block diagram showing an example of a schematic configuration of a vehicle control system.
• FIG. 34 is an explanatory diagram showing an example of the installation position of a distance measuring device.
• Light source device according to Example 1 of an embodiment of the present technology 2.
• Light source device according to Example 2 of an embodiment of the present technology 3.
• Light source device according to Example 3 of an embodiment of the present technology 4.
• Light source device according to Example 4 of an embodiment of the present technology 5.
• Light source device according to Example 5 of an embodiment of the present technology 6.
• Light source device according to Example 6 of an embodiment of the present technology 7.
• Light source device according to Example 7 of an embodiment of the present technology 8.
• Light source device according to Example 8 of an embodiment of the present technology 9.
• Light source device according to Example 9 of an embodiment of the present technology 10.
• Light source device according to Example 10 of an embodiment of the present technology 11.
• Light source device according to Example 11 of an embodiment of the present technology 12.
• Light source device according to Example 12 of an embodiment of the present technology 13.
• Light source device according to Example 13 of an embodiment of the present technology 14.
• Light source device according to Example 14 of an embodiment of the present technology 15.
• Modification of the present technology 16.
• PCSELs Photonic crystal surface-emitting lasers
• VCSELs VCSELs
• advantages not found in other semiconductor lasers including conventional surface-emitting lasers (e.g. VCSELs), such as the ability to obtain highly focused light directly from the semiconductor structure and the ability to emit coherent light over a large area.
• the inventors therefore undertook a process of trial and error to determine the layer structure and electrical connection method of the PCSEL for directly bonding the PCSEL to the laser driver, and came up with the light source device according to the present technology as a light source device in which the PCSEL is directly mounted on the laser driver.
• the inventors further pursued their studies and developed a light source device according to one embodiment as a form suitable for practical use of the light source device according to the present technology.
• Fig. 1 is a cross-sectional view of a light source device 10 according to a first example of an embodiment of the present technology.
• Fig. 2 is a schematic plan view of the light source device 10.
• Fig. 1 is a cross-sectional view taken along line P-P in Fig. 2.
• a light source device 10 includes a photonic crystal surface emitting laser 100 and a laser driver 200.
• the photonic crystal surface emitting laser is also called a "PCSEL.”
• the photonic crystal surface-emitting laser 100 is a surface-emitting laser that is flip-chip mounted on the laser driver 200. In other words, the photonic crystal surface-emitting laser 100 is mounted on the laser driver 200 in a junction-down manner.
• the photonic crystal surface-emitting laser 100 has, as an example, a plurality of (for example, four) light-emitting element units 100A in which a plurality of layers including an active layer 104 and a photonic crystal layer 105 are stacked in the stacking direction (see FIG. 2).
• the plurality of light-emitting element units 100A are arranged in the in-plane direction, and as an example, are arranged two-dimensionally in the in-plane direction.
• the plurality of light-emitting element units 100A are arranged in a matrix shape at equal intervals in the row and column directions, as an example.
• the active layer 104 and the photonic crystal layer 105 are arranged adjacent to each other in the stacking direction, as an example.
• the active layer 104 and the photonic crystal layer 105 are adjacent to each other in the stacking direction such that the photonic crystal layer 105 is on the laser driver 200 side.
• the active layer 104 and the photonic crystal layer 105 may be adjacent to each other in the stacking direction such that the active layer 104 is on the laser driver 200 side.
• the multiple light-emitting element units 100A can have different FOVs (field of view) of emitted light, for example.
• the photonic crystal surface-emitting laser 100 further has, as an example, a pedestal portion 100B aligned (e.g. adjacent) to the light-emitting element portion 100A in the in-plane direction (direction perpendicular to the stacking direction).
• both the light-emitting element portion 100A and the pedestal portion 100B are mesa-shaped.
• the light-emitting element portion 100A is also called a "light-emitting mesa" because it emits light and is mesa-shaped.
• the pedestal portion 100B is also called a "dummy mesa” because it does not emit light and is mesa-shaped.
• the photonic crystal surface-emitting laser 100 further has, as an example, first and second insulating films 113, 114 as protective films that cover the light-emitting element portion 100A and the base portion 100B.
• the first insulating film 113 is an inner insulating film that directly covers the semiconductor structure of the light-emitting element portion 100A
• the second insulating film 114 is an outer insulating film that covers the semiconductor structure of the light-emitting element portion 100A via the first insulating film 113.
• the photonic crystal surface-emitting laser 100 further includes, as an example, a substrate 101 on which a plurality of light-emitting element units 100A and a base unit 100B are protruding on the surface facing the laser driver 200.
• the substrate 101 is shared by the plurality of light-emitting element units 100A.
• the substrate 101 is located on the side opposite the laser driver 200 side of the active layer 104 and the photonic crystal layer 105.
• the photonic crystal surface-emitting laser 100 is a surface-emitting laser with a back-side emission side that emits laser light to the back side of the substrate 101 (the side opposite the laser driver 200 side).
• An AR (anti-reflection) film 110 is provided on the back side of the substrate 101.
• the laser driver 200 is electrically connected to the photonic crystal surface-emitting laser 100 via a bump. That is, as an example, the laser driver 200 is electrically and mechanically connected to the photonic crystal surface-emitting laser 100.
• the photonic crystal surface-emitting laser 100 has, as an example, first and second electrodes 109, 112 for passing electricity to the light-emitting element section 100A on the laser driver 200 side.
• the first electrode 109 is electrically connected to the laser driver 200 via a first bump BP1.
• the second electrode 112 is electrically connected to the laser driver 200 via a second bump BP2.
• the laser driver 200 has a third bump BP3 bonded to the first bump BP1 and a fourth bump BP4 bonded to the second bump BP2.
• the first to fourth bumps BP1 to BP4 are all conductive bumps.
• the laser driver 200 has a power supply and a MOSFET (Metal-Oxide-Semiconductor Field-effect Transistor) as a switching element connected to one of the first and second electrodes 109, 112 (e.g., the first electrode 109).
• MOSFET Metal-Oxide-Semiconductor Field-effect Transistor
• the laser driver 200 has a plurality of switching elements corresponding to the plurality of light-emitting element units 100A. Each of the plurality of switching elements is connected to one of the first and second electrodes 109, 112 (e.g., the first electrode 109) for passing electricity through the corresponding light-emitting element unit 100A.
• the laser driver 200 includes circuit elements such as a capacitor and a resistor.
• an n-type MOSFET (hereinafter abbreviated as "nMOS") is used as the MOSFET.
• the nMOS is provided in a p-type semiconductor substrate (e.g., a p-type silicon substrate).
• the drain of the nMOS is connected to the third bump BP3, the source is connected to the cathode side of the power supply, and a gate voltage is applied to the gate.
• the anode side of the power supply is connected to the fourth bump BP4.
• the nMOS generates a drive pulse that turns on/off the light-emitting element unit 100A and applies it to the light-emitting element unit 100A.
• the switching element can be made smaller, which leads to a smaller laser driver 200 and improved design freedom.
• the first electrode 109 is provided on the surface of the light-emitting element unit 100A facing the laser driver 200.
• the second electrode 112 is provided on the surface of the base unit 100B facing the laser driver 200.
• the first electrode 109 is a cathode electrode
• the second electrode 112 is an anode electrode.
• the photonic crystal surface-emitting laser 100 has a wiring 119 that is connected to the second electrode 112 and extends from the second electrode 112 side along the base portion 100B to the substrate 101 side.
• the wiring 119 is provided on at least the side surface of the base portion 100B.
• the photonic crystal surface-emitting laser 100 has an intermediate electrode 111 that is provided directly or indirectly (e.g., directly) on the substrate 101 and connected to wiring 119.
• the photonic crystal surface-emitting laser 100 includes a tunnel junction layer 102 as a low-resistance layer having a lower resistance than the substrate 101 on the substrate 101 side of the active layer 104 and the photonic crystal layer 105.
• the photonic crystal surface-emitting laser 100 has a first cladding layer 103 between the tunnel junction layer 102 and the active layer 104.
• the photonic crystal surface-emitting laser 100 has a reflector 107 on the laser driver 200 side of the active layer 104 and the photonic crystal layer 105.
• the photonic crystal surface-emitting laser 100 has a second cladding layer 106 between the photonic crystal layer 105 and the reflector 107.
• the photonic crystal surface-emitting laser 100 has a contact layer 108 on the side of the reflector 107 opposite the active layer 104 and photonic crystal layer 105.
• the photonic crystal surface-emitting laser 100 has, as an example, a layered structure in which a tunnel junction layer 102, a first cladding layer 103, an active layer 104, a photonic crystal layer 105, a second cladding layer 106, a reflecting mirror 107, and a contact layer 108 are layered in this order in the layering direction on a substrate 101.
• the substrate 101 is, for example, a semiconductor substrate that is transparent to the emission wavelength of the light emitting element 100A and has conductivity in the in-plane direction.
• the substrate 101 is, for example, a semiconductor substrate of a first conductivity type (for example, n-type) (for example, an n-GaAs substrate).
• the AR film 110 has, for example, a laminated structure in which a plurality of dielectric films (for example, a SiO 2 film, a SiN film, a SiON film, etc.) are laminated.
• a plurality of dielectric films for example, a SiO 2 film, a SiN film, a SiON film, etc.
• the tunnel junction layer 102 is a layer for inverting the carriers of the current.
• the tunnel junction layer 102 is provided in contact with the surface of the substrate 101 on the side of the active layer 104 and the photonic crystal layer 105.
• the tunnel junction layer 102 includes a p-type semiconductor layer 102a and an n-type semiconductor layer 102b arranged in contact with each other in the stacking direction.
• the tunnel junction layer 102 is stacked on the substrate 101 such that the n-type semiconductor layer 102b is on the substrate 101 side.
• the p-type semiconductor layer 102a is made of, for example, highly doped p-GaAs.
• the n-type semiconductor layer 102b is made of, for example, highly doped n-GaAs.
• the first cladding layer 103 is made of, for example, a first conductivity type (e.g., p-type) Alx1Ga1-x1As (0 ⁇ x1 ⁇ 1) based compound semiconductor.
• the cladding layer is also called a "spacer layer.”
• the first cladding layer 103 contains a p-type impurity such as carbon (C).
• the active layer 104 has, for example, a quantum well structure including a barrier layer and a well layer made of a GaAs-based compound semiconductor. Specifically, the active layer 104 has, for example, a multiple quantum well structure (MQW structure) formed by alternately stacking a well layer made of undoped Inx6Ga1-x6As (0 ⁇ x6 ⁇ 1) and a barrier layer made of undoped Inx1Ga1-x1As (0 ⁇ x1 ⁇ x6).
• the quantum well structure may be a single quantum well structure (QW structure).
• the emission wavelength ⁇ of the active layer 104 is, for example, 935 nm.
• the active layer is also called a "light emitting layer".
• the photonic crystal layer 105 imparts a resonance and diffraction effect due to the photonic crystal to the light emitted from the active layer 104 adjacent in the stacking direction.
• the photonic crystal layer 105 is, for example, configured by arranging modified refractive index areas 105b, which are different from the base material 105a, periodically (for example, in a lattice pattern) in a plate-shaped base material 105a.
• the period (for example, the spacing between lattice points) of the modified refractive index areas 105b is, for example, the same as the emission wavelength ⁇ of the active layer 104.
• the material of the base material 105a is, for example, GaAs, but is not limited to this.
• the modified refractive index areas 105b are, for example, holes (air or vacuum), and are provided at positions corresponding to the emission areas (for example, the center) of the active layer 104.
• the photonic crystal layer 105 due to the presence of the periodic refractive index distribution described above, light of a specific wavelength (e.g., emission wavelength ⁇ ) forms a two-dimensional standing wave state in a specific direction within the photonic crystal plane.
• a specific wavelength e.g., emission wavelength ⁇
• diffraction occurs not only in directions parallel to the photonic crystal plane but also in directions perpendicular to it, making it possible to emit a beam with a narrow emission angle in a direction perpendicular to the in-plane direction (stacking direction), thereby obtaining a surface emission output.
• the second cladding layer 106 is made of, for example, a second conductivity type (e.g., n-type) Alx2Ga1-x2As (0 ⁇ x2 ⁇ 1) based compound semiconductor.
• the cladding layer is also called a "spacer layer.”
• the second cladding layer 106 contains an n-type impurity such as phosphorus (P).
• Reflecting mirror 107 is provided to improve the light utilization efficiency by reflecting light emitted from active layer 104 and emitted to the side opposite substrate 101 through photonic crystal layer 105 toward photonic crystal layer 105.
• reflecting mirror 107 is provided for the purpose of improving efficiency and is not essential.
• the reflector 107 is, for example, a semiconductor multilayer reflector.
• a multilayer reflector is also called a distributed Bragg reflector.
• the reflector 107 is, for example, a semiconductor multilayer reflector of a first conductivity type (for example, n-type), and has a structure in which multiple types (for example, two types) of semiconductor layers with different refractive indices are alternately stacked with an optical thickness of 1/4 the emission wavelength.
• Each refractive index layer of the reflector 107 is made of an AlGaAs-based compound semiconductor of a first conductivity type (for example, n-type).
• the reflector 107 has a low refractive index layer made of, for example, n-Alx3Ga1-x3As (0 ⁇ x3 ⁇ 1), and a high refractive index layer made of, for example, n-Alx4Ga1-X4As (0 ⁇ x4 ⁇ x3).
• the contact layer 108 is a layer for making ohmic contact between the reflector 107 and the first electrode 109.
• the contact layer 108 is made of, for example, n-Alx5Ga1-x5As (0 ⁇ x5 ⁇ 1).
• the second cladding layer 106, the reflecting mirror 107, and the contact layer 108 contain n-type impurities such as silicon (Si).
• n-type impurities such as silicon (Si).
• the second cladding layer 106, the reflecting mirror 107, and the contact layer 108 are made of n-type semiconductors.
• the first and second insulating films 113, 114 are made of a dielectric material such as SiN, SiO2, or SiON. In particular, when the first and second insulating films 113, 114 are made of SiN, they contribute to suppressing moisture penetration from the outside.
• a first contact hole CH1 is provided in the first insulating film 113 on the top of the light emitting element portion 100A at a position corresponding to the light emitting region of the active layer 104, exposing the contact layer 108.
• a second contact hole CH2 is provided in the first insulating film 113 covering the region between the mesas, exposing the substrate 101.
• a third contact hole CH3 is provided in the second insulating film 114 on the top of the light emitting element portion 100A, exposing the first electrode 109.
• a fourth contact hole CH4 is provided in the second insulating film 114 on the top of the pedestal portion 100B, exposing the second electrode 112.
• the first electrode 109 is disposed at a position corresponding to the light emitting region of the active layer 104.
• the first electrode 109 is in contact with a portion of the contact layer 108 corresponding to the light emitting region of the active layer 104. Therefore, the first electrode 109 is electrically connected to the reflector 107 through the contact layer 108.
• the first electrode 109 is configured to include an alloy, for example.
• the first electrode 109 is a laminate in which a first contact electrode 109a and a first pad electrode 109b are laminated in this order from the contact layer 108 side.
• the first contact electrode 109a is provided in the first contact hole CH1 so as to be in contact with the contact layer 108.
• the first contact electrode 109a has a laminate structure in which, for example, an AuGe layer, a Ni layer, and an Au layer are laminated in this order from the contact layer 108 side.
• the first pad electrode 109b is exposed to the outside through a third contact hole CH3.
• the first pad electrode 109b has, for example, a laminated structure in which non-alloy metal films, for example, a Ti layer, a Pt layer, and an Au layer are laminated in this order from the contact layer 108 side.
• the first electrode 109 is connected to the drain of the nMOS of the laser driver 200 via the first and third bumps BP1 and BP3.
• the second electrode 112 has a layered structure in which non-alloy metal films, for example, a Ti layer, a Pt layer, and an Au layer are layered in this order from the contact layer 108 side.
• non-alloy metal films for example, a Ti layer, a Pt layer, and an Au layer are layered in this order from the contact layer 108 side.
• the second electrode 112 is connected to the anode side of the power supply of the laser driver 200 via the second and fourth bumps BP2 and BP4.
• the intermediate electrode 111 is a laminate in which a second contact electrode 111a and a second pad electrode 111b are laminated in this order from the substrate 101 side.
• the second contact electrode 111a is provided in the second contact hole CH2 so as to contact the substrate 101.
• the second contact electrode 111a has a laminate structure in which, for example, AuGe, Ni, and Au are laminated in this order from the substrate 101 side.
• the second pad electrode 111b is made of, for example, a Ti layer, an Au layer, etc., provided as a thick film on the second contact electrode 111a, and contributes to reducing the resistance of the intermediate electrode 111.
• the wiring 119 connects the second electrode 112 and the intermediate electrode 111. More specifically, the wiring 119 is provided across the side and top of the pedestal portion 100B and the side and top of the second pad electrode 111b of the intermediate electrode 111.
• the wiring 119 is made of, for example, a Ti layer, an Au layer, or the like. As an example, the wiring 119 is provided in common to a plurality of (for example, two) pedestal portions 100B (see FIG. 2).
• the first and second bumps BP1, BP2 provided on the photonic crystal surface emitting laser 100 are conductive bumps having electrical conductivity, and are made of metals such as Ag, Au, Cu, and Ni.
• the third and fourth bumps BP3, BP4 provided on the laser driver 200 are conductive bumps having electrical conductivity, and are made of Pb-free solders such as AgSn, AuSn, CuSn, NiSn, and CuNiSn.
• the first and third bumps BP1, BP3 are bonded by, for example, thermocompression bonding.
• the second and fourth bumps BP2, BP4 are bonded by, for example, thermocompression bonding.
• the operation of the light source device 10 will be described below.
• the current from the power supply of the laser driver 200 flows into the intermediate electrode 111 through the fourth bump BP4, the second bump BP2, the second electrode 112 as the anode electrode, and the wiring 119 in this order.
• the current through the intermediate electrode 111 flows in the in-plane direction in the substrate 101 and flows into the light emitting element section 100A.
• the current through the tunnel junction layer 102 and the first cladding layer 103 of the light emitting element section 100A in this order is injected into the active layer 104.
• the active layer 104 emits light, and the light forms a standing wave in the in-plane direction in the photonic crystal layer 105.
• the light is emitted from the photonic crystal layer 105 to the substrate 101 side and the opposite side to the substrate 101 side.
• the light emitted to the substrate 101 side is emitted as it is from the back surface of the substrate 101 as laser light.
• the light emitted to the side opposite to the substrate 101 side is reflected by the reflector 107 toward the substrate 101 side, and is emitted as laser light from the rear surface of the substrate 101.
• the current that has passed through the active layer 104 passes through the photonic crystal layer 105, the second cladding layer 106, the reflector 107, the contact layer 108, the first electrode 109 serving as a cathode electrode, the first bump BP1, and the third bump BP3, in this order, and is then passed to the nMOS of the laser driver 200.
• a plurality of photonic crystal surface-emitting lasers 100 are simultaneously produced on a single wafer (hereinafter, for convenience, referred to as "substrate 101"), which is the base material of the substrate 101, by a semiconductor manufacturing method using a semiconductor manufacturing apparatus.
• substrate 101 a single wafer
• the series of the plurality of photonic crystal surface-emitting lasers 100 are separated from each other by dicing to obtain chip-shaped photonic crystal surface-emitting lasers 100.
• the photonic crystal surface-emitting lasers 100 are flip-chip mounted on the laser driver 200.
• a first laminate L1 is produced (see FIG. 4). Specifically, the n-type semiconductor layer 102b of the tunnel junction layer 102, the p-type semiconductor layer 102a, the first cladding layer 103, the active layer 104, and the base material 105a of the photonic crystal layer 105 are laminated in this order on a substrate 101 (e.g., an n-GaAs substrate) as a growth substrate by an epitaxial crystal growth method such as MOCVD (Metal Organic Chemical Vapor Deposition).
• MOCVD Metal Organic Chemical Vapor Deposition
• the compound semiconductor raw materials are, for example, methyl-based organometallic gases such as trimethylaluminum (TMAl), trimethylgallium (TMGa), and trimethylindium (TMIn), and arsine (AsH3) gas
• the donor impurity raw material is, for example, disilane (Si2H6)
• the acceptor impurity raw material is, for example, carbon tetrabromide (CBr4).
• the photonic crystal layer 105 is formed (see FIG. 5). Specifically, a resist pattern for forming modified refractive index areas 105b (e.g., holes) of the photonic crystal layer 105 is formed on the first stack L1 (on the base material 105a of the photonic crystal layer 105) by photolithography, and the base material 105a is selectively etched using the resist pattern as a mask. At this time, it is preferable to use RIE (Reactive Ion Etching) using, for example, a Cl-based gas. The resist pattern is then removed.
• RIE Reactive Ion Etching
• a second laminate L2 is produced (see FIG. 6). Specifically, a second cladding layer 106, a reflecting mirror 107, and a contact layer 108 are laminated in this order by epitaxial growth again on the first laminate L1 on which the photonic crystal layer 105 has been formed, to produce a second laminate L2 that replaces the first laminate L1.
• a mesa is formed (see FIG. 7).
• a resist pattern is formed by photolithography on the second laminate L2 (see FIG. 6) for forming a mesa (light-emitting mesa) that will become the light-emitting element portion 100A and a mesa (dummy mesa) that will become the pedestal portion 100B, and the second laminate L2 is selectively etched by dry etching or wet etching using the resist pattern as a mask.
• the etching depth here is set to, for example, until it reaches the inside of the substrate 101.
• the resist pattern is then removed.
• the first insulating film 113 is formed (see FIG. 8). Specifically, the first insulating film 113 is formed on the entire surface of the second stack L2 (see FIG. 7) in which the mesa is formed, for example, by CVD (Chemical Vapor Deposition), sputtering, evaporation, etc.
• CVD Chemical Vapor Deposition
• sputtering evaporation, etc.
• the first and second contact holes CH1, CH2 are formed (see FIG. 9). Specifically, a resist pattern that opens at the positions where the first and second contact holes CH1, CH2 are to be formed is formed on the first insulating film 113 by photolithography, and the first insulating film 113 is etched, for example by dry etching, using the resist pattern as a mask to form the first and second contact holes CH1, CH2. The resist pattern is then removed.
• the first and second contact electrodes 109a, 111a are formed (see FIG. 10). Specifically, the first contact electrode 109a is formed in the first contact hole CH1, and the second contact electrode 111a is formed in the second contact hole CH2, for example, by a lift-off method. At this time, deposition, sputtering, or the like is used to form a film of the electrode material.
• the first and second pad electrodes 109b, 111b are formed (see FIG. 11). Specifically, for example, by lift-off, the first pad electrode 109b is formed on the first contact electrode 109a, and the second pad electrode 111b is formed as a thick film (for example, about 2 ⁇ m thick so as to sufficiently suppress voltage drop) on the second contact electrode 111a. At this time, for example, deposition, sputtering, etc. are used to form the film of the electrode material.
• the second electrode 112 and wiring 119 are formed (see FIG. 12). Specifically, the second electrode 112 is formed on the top of the pedestal (dummy mesa) by, for example, lift-off, and wiring 113 is formed on the side and top of the pedestal and the side and top of the second pad electrode 111b by, for example, oblique deposition, plating, or the like. This electrically connects the second electrode 112 and the intermediate electrode 111 via the wiring 119.
• the second insulating film 114 is formed (see FIG. 13). Specifically, the second insulating film 114 is formed over the entire surface by, for example, deposition, sputtering, etc.
• the third and fourth contact holes CH3 and CH4 are formed (see FIG. 14). Specifically, a resist pattern that opens at the positions where the third and fourth contact holes CH3 and CH4 are to be formed is formed on the second insulating film 114 by photolithography, and the first insulating film 114 is etched, for example by dry etching, using the resist pattern as a mask to form the third and fourth contact holes CH3 and CH4. The resist pattern is then removed.
• the substrate 101 is thinned to form the AR film 110 (see FIG. 15). Specifically, first, the back surface of the substrate 101 is thinned by grinding using, for example, a grinder or a CMP (Chemical Mechanical Polisher) device. Next, the AR film 110 is formed on the back surface of the thinned substrate 101 by, for example, sputtering or deposition. Thereafter, the substrate 101 is diced to obtain a plurality of chip-shaped photonic crystal surface-emitting lasers 100. Note that it is preferable to remove the portions of the first and second insulating films 113 and 114 to be diced before dicing.
• CMP Chemical Mechanical Polisher
• a first bump BP1 e.g., an Au bump
• a second bump BP2 e.g., an Au bump
• a third bump BP3 is attached to the nMOS position on the surface of the laser driver 200
• a fourth bump BP4 is attached to the anode side position of the power supply on the surface of the laser driver 200.
• the photonic crystal surface-emitting laser 100 and the laser driver 200 are aligned, and then the two are thermocompression-bonded (joined by applying pressure while heating). As a result, the photonic crystal surface-emitting laser 100 and the laser driver 200 are electrically and mechanically connected via the bumps.
• the light source device 10 according to Example 1 of an embodiment of the present technology includes a photonic crystal surface-emitting laser 100 (PCSEL) having at least one (e.g., a plurality of) light-emitting element units 100A in which a plurality of layers including an active layer 104 and a photonic crystal layer 105 are stacked, and a laser driver 200 electrically connected (directly) to the photonic crystal surface-emitting laser 100 via a bump.
• PCSEL photonic crystal surface-emitting laser 100
• the photonic crystal surface-emitting laser 100 is mounted on the laser driver 200 in a junction-down (flip-chip) configuration.
• the photonic crystal surface-emitting laser 100 is mounted on the laser driver 200 in a junction-down (flip-chip) configuration.
• the light source device 10 in which a PCSEL is mounted on a laser driver can emit a beam with a narrower emission angle.
• the photonic crystal surface-emitting laser 100 and the laser driver 200 are bonded via bumps.
• This enables a configuration that eliminates the resistance and impedance factors of wire wiring and the like. This not only reduces resistance during operation, but also makes it easy to input very short electrical signals of the order of nanoseconds. As a result, it becomes possible to obtain an optical waveform with very fast rising and falling edges.
• the light-emitting element section 100A is directly bonded to the nMOS, enabling the fastest possible high-speed operation.
• the photonic crystal surface-emitting laser 100 has first and second electrodes 109, 112 for passing current through the light-emitting element section 100A on the laser driver 200 side, the first electrode 109 being electrically connected to the laser driver 200 via a first bump BP1, and the second electrode 112 being electrically connected to the laser driver 200 via a second bump BP2. This makes it possible to configure a circuit for passing current from the laser driver 200 to the photonic crystal surface-emitting laser 100.
• the photonic crystal surface-emitting laser 100 has a base portion 100B aligned in the in-plane direction with the light-emitting element portion 100A, with the first electrode 109 provided on the surface of the light-emitting element portion 100A facing the laser driver 200, and the second electrode 112 provided on the surface of the base portion 100B facing the laser driver 200. This allows the first and second electrodes 109, 112 to be positioned on the current path so as to sandwich the light-emitting element portion 100A therebetween and to be easily joined directly to the laser driver 200.
• the photonic crystal surface-emitting laser 100 has a substrate 101 on which a light-emitting element section 100A and a base section 100B are protruding, and a wiring 119 that is connected to the second electrode 112 and extends from the second electrode 112 side along the base section 100B to the substrate 101 side. This allows electrical continuity between the second electrode 112 and the substrate 101 side.
• the photonic crystal surface-emitting laser 100 has an intermediate electrode 111 that is provided directly or indirectly (e.g., directly) on the substrate 101 and connected to the wiring 119.
• the intermediate electrode 111 is made of a highly conductive material, such as gold, and is provided with a sufficiently large thickness, for example, 2 ⁇ m. This can reduce the electrical resistance between the first and second electrodes 109, 112.
• the photonic crystal surface-emitting laser 100 includes a low-resistance layer that has a lower resistance than the substrate 101 on the substrate 101 side of the active layer 104 and the photonic crystal layer 105. This allows current to flow efficiently through the active layer 104.
• the substrate 101 is a semiconductor substrate (e.g., an n-GaAs substrate), and the low resistance layer is the tunnel junction layer 102. This makes it easier for current that flows through the substrate 101, for example, via the second electrode 112, the wiring 119, and the intermediate electrode 111 in this order, to flow into the light emitting element portion 100A.
• current diffusion occurs in the in-plane direction (lateral direction) in the semiconductor substrate that is the substrate 101. This allows current to be diffused sufficiently and uniformly up to the center of the light emitting element portion 100A, which has a width of, for example, several hundred ⁇ m.
• the laser driver 200 has a switching element (e.g., nMOS) connected to one of the first and second electrodes 109, 112 (e.g., the first electrode 109). This allows light emission/extinction control of the light-emitting element section 100A.
• a switching element e.g., nMOS
• the photonic crystal surface-emitting laser 100 has a number of light-emitting element units 100A arranged in the in-plane direction, and the laser driver 200 has a number of switching elements corresponding to the number of light-emitting element units 100A, and each of the number of switching elements is connected to one of the first and second electrodes 109, 112 (e.g., the first electrode 109) for passing electricity through the corresponding light-emitting element unit 100A.
• the number of light-emitting element units 100A to include at least two light-emitting element units 100A with different characteristics (e.g., emission angle, emission direction, polarization direction, output, etc.).
• the photonic crystal surface-emitting laser 100 is preferably a photonic crystal surface-emitting laser that emits a beam in a predetermined direction by modulating and arranging the position and/or size of each lattice point of the photonic crystal layer.
• the delay in the emission timing (oscillation delay) of the beam groups emitted from the same light-emitting element section 100A is approximately the same ( ⁇ 2 ps). This eliminates the need for calibration such as delay compensation in the laser driver 200, and the light source device 10 can be suitably used as a light source device to be incorporated in a distance measuring device in particular.
• the oscillation delays of the beam groups are approximately the same, it is possible to reduce the variation in distance measurement.
• the photonic crystal surface-emitting laser 100 includes a reflector 107 on the laser driver 200 side of the active layer 104 and the photonic crystal layer 105. This can improve the light utilization efficiency. To add to that, a photonic crystal surface-emitting laser that forms a two-dimensional standing wave state in the in-plane direction can achieve the desired function even without a reflector. However, because light is emitted on both sides in the stacking direction due to the nature of surface emission, providing a reflector on the laser driver 200 side makes it possible to extract the light emitted to the laser driver 200 side as back-emitted light, which could not be extracted in the past, and improves the light utilization efficiency by about two times.
• a light source device that uses a VCSEL as a light source is usually configured to include optical elements that control the divergence angle and emission direction of the light emitted by the VCSEL. This is because the light emitted by a normal VCSEL spreads, so the optical elements required include a collimating lens to focus the light on an object and a diffraction grating to split the light in various directions.
• a PCSEL is used as the light source, and a narrow beam spread angle can be achieved by the photonic crystal, so a collimating lens is not required.
• a feature of the PCSEL is that it can emit a beam in a specified direction, so a diffraction grating is not required.
• optical elements such as a collimating lens and a diffraction grating are not required has the advantage that the light source unit can be made smaller, and also leads to a reduction in the cost of the optical elements.
• the photonic crystal surface-emitting laser 100 is mounted (directly) on the laser driver 200 via bumps, so it is also excellent in terms of high-speed driving.
• Fig. 18 is a cross-sectional view of a light source device 20 according to Example 2 of an embodiment of the present technology. As shown in Fig. 18, the light source device 20 according to Example 2 has a similar configuration to the light source device 10 according to Example 1, except that the light-emitting element unit 250A of the photonic crystal surface-emitting laser 250 has a small diameter portion on the laser driver 200 side.
• a portion of the light-emitting element portion 250A on the laser driver 200 side (e.g., a portion including part of the second cladding layer 106, the reflector 107, and the contact layer 108) is a small-diameter portion having a smaller diameter (e.g., approximately the same size as the first electrode 109) than the other portions (e.g., a portion including the tunnel junction layer 102, the first cladding layer 103, the active layer 104, the photonic crystal layer 105, and other portions of the second cladding layer 106). This makes it possible to concentrate the current flowing into the light-emitting element portion 100A in the center of the light-emitting element portion 100A.
• the light source device 20 provides the same effects as the light source device 10 of the first embodiment, and also narrows the current path in the light-emitting element section 250A (specifically, restricts it to the central portion), thereby reducing leakage current that does not contribute to light emission, and thus improving the light emission efficiency.
• the light-emitting element portion may have a small diameter portion on the side opposite the laser driver 200.
• Light source device according to Example 3 of an embodiment of the present technology> 19 is a cross-sectional view of a light source device 30 according to Example 3 of an embodiment of the present technology.
• the light source device 30 according to Example 3 has a similar configuration to the light source device 10 according to Example 1, except that the photonic crystal surface emitting laser 300 has an oxide constriction layer 115 as a current constriction layer.
• the oxidized constriction layer 115 is disposed inside the first cladding layer 103.
• the oxidized constriction layer 115 is composed of, for example, p-Alx12Ga1-x12As (0 ⁇ x12 ⁇ 1).
• the oxidized constriction layer 115 has a non-oxidized region 115a and an oxidized region 115b surrounding the non-oxidized region 115a.
• the non-oxidized region 115a is a relatively high refractive index region composed of a semiconductor (e.g., p-AlGaAs) and functions as a current/light passing region.
• the oxidized region 115b is a relatively low refractive index region composed of an insulator (e.g., Al2O3) and functions as a current/light constriction region.
• the oxidized constriction layer 115 is formed by forming a mesa including a selectively oxidized layer (e.g., p-AlGaAs) as a material, and then selectively oxidizing the high concentration Al of the selectively oxidized layer from the side at high temperature under water vapor.
• a selectively oxidized layer e.g., p-AlGaAs
• the light source device 30 can achieve the same effect as the light source device 10 according to the first embodiment, and can perform current confinement with the oxide confinement layer 115 arranged in the first cladding layer 103 made of a p-type semiconductor layer in which holes with lower mobility serve as carriers.
• the photonic crystal surface emitting laser 300 is configured to inject current from the periphery of the light emitting element section 300A, so that the current injected into the active layer 104 can be confined by confining the current on the p-side. As a result, it becomes possible to inject current into a desired region (e.g., the central region) of the active layer 104. It can also perform light confinement (light trapping).
• Light source device according to Example 4 of an embodiment of the present technology> 20 is a cross-sectional view of a light source device 40 according to Example 4 of an embodiment of the present technology.
• the light source device 40 according to Example 4 has a similar configuration to the light source device 30 according to Example 3, except that the photonic crystal surface emitting laser 400 has a current spreading layer 116 and an etching stop layer 117 instead of the tunnel junction layer 102.
• the substrate 101 is a semi-insulating substrate or insulating substrate (for example, an SI substrate: Semi-Insulating Substrate), and the substrate 101 side of the active layer 104 and the photonic crystal layer 105 has a current spreading layer 116 that is a low resistance layer with a lower resistance than the substrate 101.
• the current spreading layer 116 is made of, for example, highly doped p-GaAs, and is provided in contact with the surface of the substrate 101 on the active layer 104 side.
• the etching stop layer 117 is made of, for example, InGaP, and is disposed between the current spreading layer 116 and the first cladding layer 103.
• the current spreading layer 116 is doped with p-type impurities such as Zn, Mg, Be, C, etc.
• the current applied from the laser driver 200 flows into the current diffusion layer 116 via the second electrode 112, the wiring 119, the intermediate electrode 111, and the etching stop layer 117.
• the current that flows into the current diffusion layer 116 diffuses in the in-plane direction of the current diffusion layer 116 and flows into the light emitting element section 400A via the etching stop layer 117.
• the light source device 40 since a silicon substrate is used for the substrate 101, it is possible to reduce absorption of the light emitted from the photonic crystal layer 105 as it passes through the substrate 101, thereby realizing a light source device with high light utilization efficiency.
• the light source device 40 does not need to have an etching stop layer 117 if the etching controllability during mesa formation is good (if the mesa can be formed so as not to etch the current diffusion layer 116).
• Fig. 21 is a cross-sectional view of a light source device 50 according to Example 5 of an embodiment of the present technology.
• the light source device 50 according to Example 5 has a configuration substantially similar to that of the light source device 10 according to Example 1, except that the first and second electrodes 109 and 112 are provided on the surface of the light emitting element section 500A on the laser driver 200 side, a current diffusion layer 116 is provided instead of the tunnel junction layer 102, and the conductivity types of the active layer 104 are switched on both sides of the active layer 104 in the stacking direction.
• the photonic crystal surface-emitting laser 500 has a current spreading layer 116 and a first cladding layer 103 made of an n-type semiconductor, and a second cladding layer 106, a reflecting mirror 107, and a contact layer 108 made of a p-type semiconductor.
• the current spreading layer 116 is doped with n-type impurities such as Si, Se, Te, or Ge.
• the photonic crystal surface-emitting laser 500 has a substrate 101 on which a light-emitting element section 500A is protruding, and a wiring 119 connected to the second electrode 112 and extending from the second electrode 112 side along the light-emitting element section 500A toward the substrate 101.
• the second electrode 112 is connected to the nMOS via second and fourth bumps BP2 and BP4.
• the photonic crystal surface-emitting laser 500 has an intermediate electrode 111 that is provided directly or indirectly (e.g., directly) on the substrate 101 and connected to the wiring 119.
• the photonic crystal surface-emitting laser 500 has a substrate 101 that is a semi-insulating substrate or an insulating substrate (e.g., an SI substrate), and has a current spreading layer 116 as a low-resistance layer with a lower resistance than the substrate 101 on the substrate 101 side of the active layer 104 and the photonic crystal layer 105.
• the current spreading layer 116 is made of, for example, highly doped n-GaAs, and is disposed between the substrate 101 and the first cladding layer 103.
• the intermediate electrode 111 is provided in a circumferential shape (e.g., a ring shape) so as to surround the light-emitting element portion 500A and to contact the current spreading layer 116.
• the current spreading layer 116 is provided separately for each light-emitting element portion 500A. That is, in the photonic crystal surface-emitting laser 500, multiple sets of the light-emitting element portion 500A, the first and second electrodes 109, 112, and the intermediate electrode 111 are provided in a semi-insulating state on the SI substrate as the substrate 101.
• the first electrode 109 provided at the center of the top of the light-emitting element unit 500A is an anode electrode
• the second electrode 112 provided in a circumferential shape so as to surround the first electrode 109 at the periphery of the top of the light-emitting element unit 500A is a cathode electrode.
• the first electrode 109 is connected to the anode side of the power supply of the laser driver 210 via the first and third bumps BP1 and BP3.
• the second electrode 112 is connected to the drain of the nMOS of the laser driver 210 via the second and fourth bumps BP2 and BP4.
• the first electrodes 109 of the multiple light-emitting element units 500A are directly connected to the p-type semiconductor substrate of the laser driver 210, and are in a common electrode state (anode common state) within the semiconductor substrate.
• the light source device 50 reduces light absorption by the substrate 101 and also enables the photonic crystal surface-emitting laser 500 to be miniaturized.
• a configuration using a semiconductor substrate (e.g., an n-GaAs substrate) as the substrate 101 and a tunnel junction layer 102 may be adopted.
• the tunnel junction layer 102 may be provided on the laser driver 200 side of the active layer 104 and the photonic crystal layer 105, or the conductivity type of the semiconductor layer of the light emitting element section 500A may be the same as that of the light emitting element section 100A of the light source device 10 according to the first embodiment, with the second electrode 112 serving as an anode electrode and the first electrode 109 serving as a cathode electrode connected to an nMOS.
• Light source device according to Example 6 of an embodiment of the present technology> 23 is a cross-sectional view of a light source device 60 according to Example 6 of an embodiment of the present technology.
• the light source device 60 according to Example 6 has a similar configuration to the light source device 50 according to Example 5, except that the conductivity types of the photonic crystal surface-emitting laser 600 are switched on both sides of the active layer 104, the first electrode 109 is a cathode electrode, and the second electrode 112 is an anode electrode.
• an nMOS is connected to the cathode electrode serving as the first electrode 109.
• the light source device 60 can achieve the same effects as the light source device 50 of Example 5.
• Light source device according to Example 7 of an embodiment of the present technology> 24 is a cross-sectional view of a light source device 70 according to Example 7 of an embodiment of the present technology.
• the light source device 70 according to Example 7 has a configuration substantially similar to that of the light source device 50 according to Example 5, except that the conductivity type of the switching element of the laser driver 230 is different.
• a pMOS (p-type MOSFET) is provided in the laser driver 230 instead of an nMOS, and the pMOS is connected to the anode electrode serving as the first electrode 109.
• the light source device 70 can achieve the same effects as the light source device 50 of Example 5.
• Light source device according to Example 8 of an embodiment of the present technology> 25 is a cross-sectional view of a light source device 80 according to Example 8 of an embodiment of the present technology.
• the light source device 80 according to Example 8 has a similar configuration to the light source device 60 according to Example 6, except that the conductivity type of the switching element of the laser driver 230 is different.
• a pMOS (p-type MOSFET) is provided in the laser driver 230 instead of an nMOS, and the pMOS is connected to the anode electrode serving as the second electrode 112.
• the light source device 80 can achieve the same effects as the light source device 60 according to the sixth embodiment.
• Light source device according to Example 9 of an embodiment of the present technology> 26 is a cross-sectional view of a light source device 90 according to Example 9 of an embodiment of the present technology.
• the light source device 90 according to Example 9 has a similar configuration to the light source device 50 according to Example 5, except that an ion implantation region 118 is provided as a current confinement region in the light emitting element section 500A.
• the ion implantation region 118 is provided in a circumferential (e.g., annular) shape around the periphery of the first cladding layer 103, the active layer 104, and the photonic crystal layer 105.
• the light source device 90 allows current confinement using the ion implantation region 118, improving the efficiency of current injection into the active layer 104 and thus improving the light emission efficiency of the active layer 104.
• the ion implantation region IIA may be provided in at least a portion of the light emitting element section 500A in the stacking direction.
• the ion implantation region IIA may be provided in the peripheral areas of the second cladding layer 106, the reflector 107, and the contact layer 108 instead of or in addition to the peripheral areas of the first cladding layer 103, the active layer 104, and the photonic crystal layer 105.
• Light source device according to Example 10 of an embodiment of the present technology> 27 is a cross-sectional view of a light source device 120 according to Example 10 of an embodiment of the present technology.
• the light source device 120 according to Example 10 has a similar configuration to the light source device 10 according to Example 1, except that the photonic crystal surface-emitting laser 700 has one light-emitting element portion 100A and one base portion 100B.
• the laser driver 240 has one nMOS, and the nMOS is connected to the light emitting element section 100A via the first and third bumps BP1 and BP3.
• the light source device 120 can provide a light source device having a single light-emitting element section 100A that is configured from a portion of the light source device 10 according to the first embodiment.
• Light source device according to Example 11 of an embodiment of the present technology> 28 is a cross-sectional view of a light source device 130 according to Example 11 of an embodiment of the present technology.
• the light source device 130 according to Example 11 has a similar configuration to the light source device 120 according to Example 10, except that the laser driver 255 has one pMOS, and the pMOS is connected to the base part 100B via the second and fourth bumps BP2 and BP4.
• the light source device 130 can achieve the same effects as the light source device 120 of Example 10.
• Light source device according to Example 12 of an embodiment of the present technology> 29 is a cross-sectional view of a light source device 140 according to Example 12 of an embodiment of the present technology.
• the light source device 140 according to Example 12 has a similar configuration to the light source device 50 according to Example 5, except that the photonic crystal surface-emitting laser 800 has a single light-emitting element portion 500A.
• the laser driver 260 has one nMOS, and the nMOS is connected to the second electrode 112 (cathode electrode) of the light emitting element section 500A via the second and fourth bumps BP2 and BP4.
• the light source device 140 can provide a light source device having a single light-emitting element unit 500A that is configured as part of the light source device 50 according to the fifth embodiment.
• Light source device according to Example 13 of an embodiment of the present technology> 30 is a cross-sectional view of a light source device 150 according to Example 13 of an embodiment of the present technology.
• the light source device 150 according to Example 13 has a photonic crystal surface-emitting laser 900 in which the conductivity types on both sides in the stacking direction of the active layer are switched, and a laser driver 270 is connected to a first electrode 109 (cathode electrode) via first and third bumps BP1 and BP3.
• the light source device 140 according to the twelfth embodiment has the same configuration as the light source device 140 according to the twelfth embodiment.
• the light source device 150 provides the same effects as the light source device 140 of Example 12.
• Light source device according to Example 14 of an embodiment of the present technology> 31 is a cross-sectional view of a light source device 160 according to Example 14 of an embodiment of the present technology.
• the light source device 160 according to Example 14 has a configuration substantially similar to that of the light source device 10 according to Example 1, except that the first and third bumps BP1 and BP3 connecting the light emitting element unit 700A of the photonic crystal surface emitting laser 1100 to the laser driver 200 are provided with a size equivalent to the entire top of the light emitting element unit 700A.
• the first and third contact holes CH1 and CH3 are provided over substantially the entire area of the top of the light-emitting element section 700A, and the first electrode 109 is provided over substantially the entire area within the first and third contact holes CH1 and CH3.
• the first and third bumps BP1, BP3 are provided corresponding to almost the entire area of the light emitting element section 700A, so that the light source device 160 has excellent heat dissipation properties.
• bumps are provided on both the photonic crystal surface-emitting laser and the laser driver, but this is not limiting, and the point is that bumps should be provided on at least one of the photonic crystal surface-emitting laser and the laser driver.
• the bumps provided on the photonic crystal surface-emitting laser and the laser driver are made of different materials, but they may be made of the same material (including the same material).
• a semiconductor multilayer film reflector is used as the reflector, but this is not limited thereto.
• a dielectric multilayer film reflector or a hybrid mirror including at least two of a semiconductor multilayer film reflector, a dielectric multilayer film reflector, and a metal reflector may be used.
• the photonic crystal surface emitting laser is made of a material that is lattice-matched to GaAs, but this is not limiting, and materials that are lattice-matched to GaN or InP may also be used.
• the layer structure of the first and second electrodes 109, 112 can be changed as appropriate.
• the contact layer 108 does not have to be provided.
• Reflector 107 does not have to be provided.
• planar shape of the light-emitting element portion and the base portion is not limited to a circle, but may be, for example, a polygon, an ellipse, etc.
• a MOSFET is used as the switching element of the laser driver, but other field effect transistors such as a junction FET or a bipolar transistor may also be used.
• Parts of the configurations of the light source devices in each of the above embodiments may be combined within the limits of not mutually contradicting each other.
• the material, conductivity type, thickness, width, value, shape, size, etc. of each layer constituting the photonic crystal surface emitting laser and laser driver of the light source device can be changed as appropriate within the range that allows the light source device to function.
• the technology according to the present disclosure can be applied to various products (electronic devices).
• the technology according to the present disclosure may be realized as a device mounted on any type of moving body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a ship, a robot, or a low-power device (e.g., a smartphone, a smart watch, a tablet, a mouse, etc.).
• the light source device can also be used as a light source for devices that form or display images using laser light (e.g., laser printers, laser copiers, projectors, head-mounted displays, head-up displays, etc.).
• laser light e.g., laser printers, laser copiers, projectors, head-mounted displays, head-up displays, etc.
• Example of application of light source device to distance measuring device An application example of the light source device 10 according to the first embodiment will be described below.
• FIG. 32 shows an example of the schematic configuration of a distance measurement device 1000 (distance measuring device) equipped with a light source device 10, as an example of an electronic device related to the present technology.
• the distance measurement device 1000 measures the distance to a subject S using a TOF (Time Of Flight) method.
• the distance measurement device 1000 is equipped with a light source device 10.
• the distance measurement device 1000 is equipped with, for example, a light source device 10, a light receiving device 125, lenses 128, 130, a signal processing unit 145, a control unit 155, a display unit 165, and a memory unit 170.
• the light receiving device 125 receives the light emitted from the light source device 10 and reflected by the specimen S (object). That is, the light receiving device 125 detects the light reflected by the specimen S.
• the lens elements constituting the lens 128 are lenses for collimating the light emitted from the photonic crystal surface-emitting laser 100, for example, collimating lenses. Since the light emitted from the photonic crystal surface-emitting laser 100 is collimated from the beginning due to its characteristics, the minimum number of lenses 128 is sufficient to obtain the desired beam quality, and it is possible to use fewer lenses than in a conventional surface-emitting laser (for example, VCSEL).
• the photonic crystal surface-emitting laser 100 has a function of being able to emit multiple beams in a desired direction, and has a function similar to that of a diffraction grating. In normal use, this function is included in the external lens 128.
• the lens 130 is a lens for collecting the light reflected by the specimen S and guiding it to the light receiving device 125, for example, a collecting lens.
• the signal processing unit 145 is a circuit for generating a signal corresponding to the difference between the signal input from the light receiving device 125 and the reference signal input from the control unit 155.
• the control unit 155 is configured to include, for example, a Time to Digital Converter (TDC).
• TDC Time to Digital Converter
• the reference signal may be a signal input from the control unit 155, or may be an output signal of a detection unit that directly detects the output of the photonic crystal surface emitting laser 100.
• the control unit 155 is, for example, a processor that controls the photonic crystal surface emitting laser 100, the light receiving device 125, the signal processing unit 145, the display unit 165, and the storage unit 170.
• the control unit 155 is a circuit that measures the distance to the specimen S based on the signal generated by the signal processing unit 145.
• the control unit 155 generates a video signal for displaying information about the distance to the specimen S and outputs it to the display unit 165.
• the display unit 165 displays information about the distance to the specimen S based on the video signal input from the control unit 155.
• the control unit 155 stores information about the distance to the subject S in the memory unit 170.
• any of the light source devices 20, 30, 40, 50, 60, 70, 80, 90, 120, 130, 140, 150, and 160 can also be applied to the distance measurement device 1000.
• FIG. 33 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.
• the vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001.
• the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside vehicle information detection unit 12030, an inside vehicle information detection unit 12040, and an integrated control unit 12050.
• Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio/video output unit 12052, and an in-vehicle network I/F (interface) 12053.
• the drive system control unit 12010 controls the operation of devices related to the drive system of the vehicle according to various programs.
• the drive system control unit 12010 functions as a control device for a drive force generating device for generating the drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force for the vehicle.
• the body system control unit 12020 controls the operation of various devices installed in the vehicle body according to various programs.
• the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, tail lamps, brake lamps, turn signals, and fog lamps.
• radio waves or signals from various switches transmitted from a portable device that replaces a key can be input to the body system control unit 12020.
• the body system control unit 12020 accepts the input of these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.
• the outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000.
• a distance measurement device 12031 is connected to the outside-vehicle information detection unit 12030.
• the distance measurement device 12031 includes the distance measurement device 1000 described above.
• the outside-vehicle information detection unit 12030 causes the distance measurement device 12031 to measure the distance to an object outside the vehicle (subject S), and acquires the distance data obtained thereby.
• the outside-vehicle information detection unit 12030 may perform object detection processing of people, cars, obstacles, signs, etc. based on the acquired distance data.
• the in-vehicle information detection unit 12040 detects information inside the vehicle.
• a driver state detection unit 12041 that detects the state of the driver is connected.
• the driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the driver's degree of fatigue or concentration based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.
• the microcomputer 12051 can calculate control target values for the driving force generating device, steering mechanism, or braking device based on information inside and outside the vehicle acquired by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040, and output control commands to the drive system control unit 12010.
• the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning.
• ADAS Advanced Driver Assistance System
• the microcomputer 12051 can also control the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle acquired by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040, thereby performing cooperative control aimed at automatic driving, which allows the vehicle to travel autonomously without relying on the driver's operation.
• the microcomputer 12051 can also output control commands to the body system control unit 12020 based on information outside the vehicle acquired by the outside-vehicle information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside-vehicle information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching high beams to low beams.
• the audio/image output unit 12052 transmits at least one output signal of audio and image to an output device capable of visually or audibly notifying the occupants of the vehicle or the outside of the vehicle of information.
• an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices.
• the display unit 12062 may include, for example, at least one of an on-board display and a head-up display.
• Figure 34 shows an example of the installation location of the distance measuring device 12031.
• the vehicle 12100 has distance measurement devices 12101, 12102, 12103, 12104, and 12105 as the distance measurement device 12031.
• the distance measuring devices 12101, 12102, 12103, 12104, and 12105 are provided, for example, on the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100.
• the distance measuring device 12101 provided on the front nose and the distance measuring device 12105 provided on the top of the windshield inside the vehicle cabin mainly obtain data in front of the vehicle 12100.
• the distance measuring devices 12102 and 12103 provided on the side mirrors mainly obtain data on the sides of the vehicle 12100.
• the distance measuring device 12104 provided on the rear bumper or back door mainly obtains data on the rear of the vehicle 12100.
• the forward data obtained by the distance measuring devices 12101 and 12105 is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, etc.
• FIG. 34 shows an example of the detection ranges of the distance measuring devices 12101 to 12104.
• Detection range 12111 indicates the detection range of the distance measuring device 12101 provided on the front nose
• detection ranges 12112 and 12113 indicate the detection ranges of the distance measuring devices 12102 and 12103 provided on the side mirrors, respectively
• detection range 12114 indicates the detection range of the distance measuring device 12104 provided on the rear bumper or back door.
• the microcomputer 12051 can determine the distance to each three-dimensional object within the detection ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100) based on the distance data obtained from the distance measuring devices 12101 to 12104, and can extract as a preceding vehicle, in particular, the closest three-dimensional object on the path of the vehicle 12100 that is traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km/h or faster). Furthermore, the microcomputer 12051 can set the inter-vehicle distance that should be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control) and automatic acceleration control (including follow-up start control). In this way, cooperative control can be performed for the purpose of automatic driving, which runs autonomously without relying on the driver's operation.
• automatic braking control including follow-up stop control
• automatic acceleration control including follow-up start control
• the microcomputer 12051 classifies and extracts three-dimensional object data on three-dimensional objects, such as two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects, based on the distance data obtained from the distance measuring devices 12101 to 12104, and can use the data to automatically avoid obstacles.
• the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see.
• the microcomputer 12051 determines the collision risk, which indicates the degree of risk of collision with each obstacle, and when the collision risk is equal to or exceeds a set value and there is a possibility of a collision, it can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.
• the above describes an example of a mobile object control system to which the technology disclosed herein can be applied.
• the technology disclosed herein can be applied to the distance measuring device 12031 of the configuration described above.
• a photonic crystal surface emitting laser having at least one light emitting element portion in which a plurality of layers including an active layer and a photonic crystal layer are stacked; a laser driver electrically connected to the photonic crystal surface emitting laser via a bump;
• a light source device comprising: (2) The light source device described in (1), wherein the photonic crystal surface-emitting laser has first and second electrodes on the laser driver side for passing electricity through the light-emitting element portion, the first electrode being electrically connected to the laser driver via a first bump, and the second electrode being electrically connected to the laser driver via a second bump.
• the photonic crystal surface-emitting laser has a base portion aligned in an in-plane direction with the light-emitting element portion, the first electrode is provided on a surface of the light-emitting element portion facing the laser driver, and the second electrode is provided on a surface of the base portion facing the laser driver.
• the photonic crystal surface-emitting laser has a substrate on which the light-emitting element portion and the base portion are protruded, and wiring connected to the second electrode and extending from the second electrode side along the base portion to the substrate side.
• the light source device wherein the photonic crystal surface emitting laser has an intermediate electrode that is provided directly or indirectly on the substrate and connected to the wiring.
• the light source device according to (4) or (5), wherein the photonic crystal surface emitting laser includes a low resistance layer having a lower resistance than the substrate on the substrate side of the active layer and the photonic crystal layer.
• the light source device wherein the substrate is a semiconductor substrate, and the low resistance layer is a tunnel junction layer.
• the light source device is a semi-insulating substrate or an insulating substrate, and the low resistance layer is a current spreading layer.
• the light source device described in (2) wherein the first electrode is provided on a surface of the light-emitting element portion facing the laser driver, and the second electrode is provided on a surface of the light-emitting element portion facing the laser driver.
• the photonic crystal surface emitting laser has a substrate on which the light emitting element portion is protruding, and wiring connected to the second electrode and extending from the second electrode side along the light emitting element portion toward the substrate side.
• the photonic crystal surface emitting laser has an intermediate electrode that is provided directly or indirectly on the substrate and connected to the wiring.
• the light source device (12) The light source device according to (10) or (11), wherein the photonic crystal surface emitting laser includes a low resistance layer having a lower resistance than the substrate on the substrate side of the active layer and the photonic crystal layer. (13) The light source device according to (12), wherein the substrate is a semiconductor substrate, and the low resistance layer is a tunnel junction layer. (14) The light source device according to (12), wherein the substrate is a semi-insulating substrate or an insulating substrate, and the low resistance layer is a current spreading layer. (15) The light source device according to any one of (2) to (14), wherein the laser driver has a switching element connected to one of the first and second electrodes.
• the photonic crystal surface emitting laser includes a current confinement layer.
• the photonic crystal surface emitting laser includes a reflecting mirror on the laser driver side of the active layer and the photonic crystal layer.

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