WO2012161199A1 - 光デバイス - Google Patents
光デバイス Download PDFInfo
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- WO2012161199A1 WO2012161199A1 PCT/JP2012/063091 JP2012063091W WO2012161199A1 WO 2012161199 A1 WO2012161199 A1 WO 2012161199A1 JP 2012063091 W JP2012063091 W JP 2012063091W WO 2012161199 A1 WO2012161199 A1 WO 2012161199A1
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- WIPO (PCT)
- Prior art keywords
- wavelength conversion
- conversion element
- optical device
- optical waveguide
- heater
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- 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
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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
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- 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
- G02F1/3505—Coatings; Housings; Supports
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- 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
- G02F2203/00—Function characteristic
- G02F2203/21—Thermal instability, i.e. DC drift, of an optical modulator; Arrangements or methods for the reduction thereof
Definitions
- the present invention relates to an optical device in which an optical element in which an optical waveguide is formed is bonded to a substrate.
- the short wavelength laser light source is a wavelength conversion element that converts infrared light of a fundamental wave oscillated by a laser element as an optical device into a second harmonic, and outputs laser light such as blue or green.
- the wavelength conversion element uses crystal materials such as LN (lithium niobate: LiNbO3) and LT (lithium tantalate: LiTaO3), but the conversion efficiency of harmonics is dependent on temperature, and the environmental temperature fluctuates. Has a characteristic that the conversion efficiency changes significantly.
- FIG. 26A is a graph showing an example of change in harmonic output (HFO) with respect to the environmental temperature (T) of the wavelength conversion element.
- HFO harmonic output
- T environmental temperature
- the output of the wavelength conversion element decreases in the region where the environmental temperature is low, and the output also decreases in the region where the environmental temperature is high. Since the harmonics output from the wavelength conversion element largely change with temperature, the temperature characteristics of the wavelength conversion element are corrected in order to realize efficient conversion and obtain stable harmonic laser light. A means of temperature characteristic correction is essential.
- the laser light source which mounts a heater in a wavelength conversion element is known (for example, refer to patent documents 1).
- FIG. 26 (b) is a view showing the short wavelength laser light source disclosed in Patent Document 1.
- the short wavelength laser light source has a 0.8 ⁇ m band semiconductor laser 410 and a wavelength conversion element 420 on a silicon substrate 401.
- the fundamental wave 412 is output from the active layer 411 of the semiconductor laser 410 and is incident on the optical waveguide 121 of the wavelength conversion element 420, and the blue laser light 430 which is the second harmonic is output.
- a groove 402 is formed by etching on part of the surface of the silicon substrate 401 in contact with the wavelength conversion element 420.
- a thin film heater 422 made of a Ti film is formed in the lower part of the wavelength conversion element 420, that is, in the vicinity of the optical waveguide 421.
- the temperature of the wavelength conversion element 420 can be maintained at a predetermined temperature.
- the thin film heater 422 is not in contact with the silicon substrate 401 due to the groove 402 of the silicon substrate 401, the heat of the thin film heater 422 is not easily transmitted to the silicon substrate 401.
- JP-A-6-338650 page 5, FIG. 5
- JP-A-2000-244048 page 3, FIGS. 1 and 2
- the groove 402 is formed in the silicon substrate 401 by etching or the like in order to thermally shut off the optical waveguide 421 and the silicon substrate 401. For this reason, the silicon substrate 401 requires an etching process, and the manufacturing process is complicated.
- the air layer 403 inside the groove 402 of the silicon substrate 401 is heated in some cases and is cooled in some cases.
- the air layer 403 repeats expansion and contraction, but since the air layer 403 does not have a flow path from the silicon substrate 401 to the outside, pressure changes repeatedly occur in the air layer 403.
- the present invention aims to provide an optical device for solving the above problems.
- a gap is formed between the optical waveguide and the substrate without providing a groove or the like in the substrate, and light is not stressed on the optical element even if it is heated by the heater for temperature control. Intended to provide a device.
- Still another object of the present invention is to provide a highly reliable optical device by preventing the adhesion of dust to the optical waveguide.
- Still another object of the present invention is to provide an optical device capable of efficiently performing partial temperature control of an optical waveguide.
- the optical device comprises a substrate, an optical element having an optical waveguide formed on the surface facing the substrate, a junction formed on the substrate so as to sandwich the optical waveguide and heating the optical waveguide. It has a heater formed on at least one of an optical element or a substrate and a micro bump structure made of a metal material, and is joined via the micro bump structure so that a gap is formed between the optical waveguide and the substrate It is characterized in that the part and the optical element are joined.
- the micro bump structure has a gap that allows air to be taken in and out from the gap formed between the optical waveguide and the substrate.
- the heater is preferably formed on the surface facing the substrate of the optical element.
- the microbump structure is preferably made of Au and formed on the bonding portion, and the optical element preferably has an Au film for bonding to the microbump structure.
- columnar protrusions having a height of 1 to 5 ⁇ m and a diameter of 2 to 10 ⁇ m be formed at an interval of 5 to 30 ⁇ m.
- the heater is preferably composed of an ITO film or an InTiO film.
- the heater is preferably formed in a strip shape along the longitudinal direction of the optical waveguide, and preferably further includes lead portions provided at predetermined intervals in the longitudinal direction of the heater for applying a voltage to the heater.
- the lead-out portion preferably has a connecting portion that is formed to be thicker as it gets farther from the heater.
- the optical device it is preferable to further include voltage application means for applying a pulse width modulation type voltage to the lead-out portion.
- an optical element is bonded to a substrate by a micro bump structure made of a metal material.
- a micro bump structure made of a metal material.
- an optical element and a substrate are bonded by a bonding portion having a micro bump structure positioned with an optical waveguide interposed therebetween. For this reason, since the flow path of the air layer around the optical waveguide can be secured by the gap inside the micro bump, the pressure change of the air layer due to the heating of the heater can be suppressed and the stress can be prevented from being applied to the optical element. . As a result, the occurrence of distortion of the optical element due to the pressure change of the air layer can be prevented, and problems such as deterioration of wavelength conversion characteristics and output reduction due to misalignment of the optical element can be solved.
- the micro bump structure is a structure in which a large number of very thin and narrow flat gaps are formed, dust such as dust or foreign matter can not pass through the micro bumps even if air flows through the gaps. It is possible to prevent dust from adhering to the periphery of the optical waveguide. As a result, it is possible to prevent the characteristic variation of the optical element due to the influence of the adhesion of dust and the like, and to provide a highly reliable optical device having stable characteristics for a long period of time.
- the optical device comprises an ITO film or an InTiO film as a heater for adjusting the temperature of the optical device
- the ITO film or the InTiO film is transparent, so the optical waveguide is disposed even in the vicinity of the optical waveguide of the optical device.
- the temperature characteristics of the optical element can be corrected efficiently and accurately without adversely affecting the characteristics of
- the optical device may have at least three lead portions provided at predetermined intervals to apply a voltage to the heater formed in a strip shape along the longitudinal direction of the optical waveguide.
- the heater is divided into regions of predetermined resistances R, and the lead-outs are connected to both ends of each resistance R, and the current flowing through the resistances R of the divided heaters according to the voltage applied to each terminal lead-out.
- the optical device it is possible to apply a phase-shifted rectangular wave to each control voltage terminal by performing pulse width modulation control on the current supplied to the heater. In that case, compared with analog (peak value) control, it becomes possible to easily realize precise temperature control by digital control using a simple digital circuit.
- FIG. 1 is a diagram schematically illustrating the entire configuration of an optical device 1; It is AA 'cross section figure of the optical device 1 shown in FIG. It is a top view of the optical device 1 shown in FIG. It is a typical perspective view explaining that silicon substrate 10 and wavelength conversion element 20 are joined by microbumps. It is a typical side view explaining that silicon substrate 10 and wavelength conversion element 20 are joined by microbumps. It is a figure for demonstrating the alignment adjustment of the height direction by a micro bump. It is a typical expansion top view of optical device 1 for explaining circulation of air near the optical waveguide. It is a figure which shows the example of micro bump 30a, 30b which has a grid-like arrangement
- FIG. 5 is a cross-sectional view of another optical device 100.
- FIG. FIG. 5 is an enlarged top view of a part of the wavelength conversion element 20 of the optical device 100.
- FIG. 10 is a cross-sectional view of still another optical device 110.
- FIG. 11 is a top view schematically showing a silicon substrate 10 and a wavelength conversion element 20 of the optical device 110 shown in FIG. 10.
- FIG. 16 is a diagram schematically showing the overall configuration of another optical device 200.
- FIG. 6 is a plan view of the optical device 200. It is D-D 'sectional drawing of FIG. FIG. 6 is a plan view of the wavelength conversion element 201.
- FIG. 5 is a plan view of a silicon substrate 207.
- FIG. 6 is a perspective view illustrating that the silicon substrate 207 and the wavelength conversion element 201 are bonded by the micro bumps 330.
- FIG. 6 is a side view illustrating that the silicon substrate 207 and the wavelength conversion element 201 are bonded by the micro bumps 330.
- It is an explanatory view showing the composition of a part of optical device 209. As shown in FIG. It is explanatory drawing which shows the example of application of the voltage to each terminal Ta and Tb. It is a figure which shows the example of control in case there is no phase difference in the voltage applied to terminal Ta, and the voltage applied to terminal Tb.
- FIG. 16 is a plan view of a wavelength conversion element 301 in still another optical device 300. It is sectional drawing of the wavelength conversion element 301 shown in FIG. It is a figure which shows the modification of the wavelength conversion element 301 shown in FIG. It is a figure for demonstrating the detection system of a heater applied voltage. It is a figure for demonstrating the other detection system of a heater applied voltage. It is a graph which shows an example of the change of the harmonic output (HFO) with respect to the environmental temperature (T) of a wavelength conversion element. It is a figure which shows the short wavelength laser light source disclosed by patent document 1.
- an optical device will be described by taking an optical device mounted with a wavelength conversion element for converting incident light into a second harmonic as an example.
- the invention is not limited to the embodiments described in the drawings or below.
- FIG. 1 is a diagram schematically showing the overall configuration of the optical device 1.
- the optical device 1 is a plate-like silicon substrate 10, a wavelength conversion element 20 as an optical element joined onto the silicon substrate 10, and a semiconductor joined onto the silicon substrate 10 and emitting laser light.
- the laser 3 and the substrate 4 bonded to the silicon substrate 10 to fix the optical fiber 5 are provided.
- the optical device 1 has a ridge type wavelength conversion element mounted as an optical element, and a heater for adjusting the temperature of the wavelength conversion element as temperature characteristic correction means is formed of an ITO film covering the entire lower surface of the wavelength conversion element.
- the semiconductor laser 3 emits a fundamental wave (not shown) of infrared light when supplied with a drive voltage from the silicon substrate 10 by means not shown.
- the wavelength conversion element 20 receives infrared light from the semiconductor laser 3 from the entrance 22 a of the optical waveguide 22 (indicated by a broken line), converts the light into harmonics inside the optical waveguide 22, and converts it into green light or blue light.
- the laser beam L 1 is emitted from the emission port 22 b of the optical waveguide 22 and emitted to the optical fiber 5.
- the laser beam L1 incident on the optical fiber 5 passes through the optical fiber 5 and is transmitted to an external optical system (not shown).
- the semiconductor laser 3 oscillates infrared light with a wavelength of 1064 nm, and the wavelength conversion element 20 converts it into green laser light with a wavelength of 532 nm.
- the semiconductor laser 3 oscillates infrared light with a wavelength of 860 nm, and the wavelength conversion element 20 converts it into blue laser light with a wavelength of 430 nm.
- the optical device 1 can be used for a light source device such as a small projector using a laser beam as a light source.
- the external view of the optical device 1 shown in FIG. 1 is also applicable to the other optical devices 100 and 110 described later.
- FIG. 2 is a cross-sectional view of the optical device 1 shown in FIG.
- the wavelength conversion element 20 of the optical device 1 is a ridge type wavelength conversion element of SHG crystal whose main component is lithium niobate (LiNbO3).
- the optical waveguide 22 is formed in the protrusion 21c between the recesses 21a and 21b.
- the optical waveguide 22 is formed on the surface facing the silicon substrate 10 along the longitudinal direction substantially at the center of the lower part of the wavelength conversion element 20.
- the optical waveguide 22 has a function of receiving the fundamental wave from the semiconductor laser 3 (see FIG. 1), converting it into a harmonic and emitting it.
- the entire lower surface of the wavelength conversion element 20 is covered with a thin indium oxide film 25 (hereinafter referred to as the ITO film 25).
- the ITO film 25 is disposed on the surface facing the silicon substrate 10 on the entire lower surface including the surfaces of the concave portions 21a and 21b and the convex portion 21c.
- the ITO film 25 has a function as a heater for heating the optical waveguide 22 as a temperature characteristic correction unit of the wavelength conversion element 20.
- Au films 23 a and 23 b are formed on the flat portions 20 a and 20 b which are left and right on the lower surface of the wavelength conversion element 20 in the drawing.
- the Au films 23a and 23b are formed on the surface of the ITO film 25 formed on the flat portions 20a and 20b.
- the first and second junctions are excellent in conductivity and thermal conductivity, and have a predetermined thickness, at positions facing the flat portions 20a and 20b of the wavelength conversion element 20 on the top surface of the silicon substrate 10 and sandwiching the optical waveguide 22 Micro bumps 30a and 30b made of Au having a thickness are respectively formed.
- the silicon substrate 10 and the wavelength conversion element 20 are joined at room temperature activation.
- the wavelength conversion element 20 is mounted on the silicon substrate 10 with the optical waveguide 22 facing the silicon substrate 10 (face down) and with the optical waveguide 22 close to the silicon substrate 10. Since the micro bumps 30a and 30b are made of Au excellent in conductivity and thermal conductivity, the wavelength conversion element 20 and the silicon substrate 10 can be surely mechanically, electrically and thermally by the micro bumps 30a and 30b. Combined.
- a gap 26 by an air layer exists between the wavelength conversion element 20 and the silicon substrate 10.
- the optical waveguide 22 located below the wavelength conversion element 20 is not in contact with the silicon substrate 10 due to the gap 26.
- the left, right, and lower surfaces around the optical waveguide 22 are covered with an air layer by a gap 26. Due to the presence of the gap 26, three surfaces on the left, right, and lower sides around the optical waveguide 22 become air layers, and light can be confined to the optical waveguide 22 using the difference in refractive index between the air layer and the optical waveguide 22.
- the three surfaces on the left and right and the lower surface of the optical waveguide 22 are covered with the ITO film 25.
- the ITO film 25 is thin and transparent, the ITO film 25 hardly affects the characteristics of the optical waveguide 22.
- the reason why the gap 26 can be formed between the wavelength conversion element 20 and the silicon substrate 10 is that the wavelength conversion element 20 and the silicon substrate 10 are joined by the microbumps 30a and 30b, and the microbumps 30a and 30b have a predetermined thickness. It is because it has. That is, the wavelength conversion element 20 is bonded to the silicon substrate 10 at a distance corresponding to the thickness of the micro bumps 30 a and 30 b.
- the microbumps 30 a and 30 b having a predetermined thickness mechanically, electrically and thermally couple the wavelength conversion element 20 and the silicon substrate 10, and form a gap for forming an air layer around the optical waveguide 22. It also has the ability to secure 26.
- the ITO film 25 When a predetermined current is supplied from the silicon substrate 10 to the ITO film 25 through the microbumps 30a and 30b by means not shown, the ITO film 25 generates heat because it has a predetermined electric resistance. Therefore, the optical waveguide 22 covered with the ITO film 25 can be efficiently heated. Since the ITO film 25 is a solid pattern covering the entire lower surface of the wavelength conversion element 20, the entire optical waveguide 22 can be uniformly heated uniformly, and the laser light from the wavelength conversion element 20 can be used even if the environmental temperature changes. The output can be stabilized.
- the ITO film 25 can be brought close to the optical waveguide 22 because the ITO film 25 is transparent. That is, even when the laser beam strikes the ITO film 25 which is a heater during alignment of the semiconductor laser 3 and the wavelength conversion element 20, the ITO film 25 is not heated and burned by the laser beam. Therefore, the ITO film 25 as a heater can be formed in contact with the optical waveguide 22, and the optical waveguide 22 can be efficiently heated and temperature controlled.
- the microbumps 30 a and 30 b are formed evenly on the left and right sides of the optical waveguide 22 of the wavelength conversion element 20, and the microbumps are not arranged directly under or near the optical waveguide 22. Is adopted. There are three reasons for this:
- the optical waveguide 22 of the wavelength conversion element 20 confines light inside using a refractive index difference with the surrounding area (air layer).
- a metal such as a micro bump directly contacts the optical waveguide 22
- the optical waveguide 22 changes its refractive index difference with the surroundings, and light can not be confined as designed, and the performance of the optical waveguide 22 is degraded.
- the microbumps 30a and 30b are formed in the area other than the area immediately below the optical waveguide 22 without arranging the microbumps immediately below and in the vicinity of the optical waveguide 22. Therefore, in the optical device 1, since the microbumps are not in direct contact with the optical waveguide 22, the difference in refractive index between the optical waveguide 22 and the surroundings does not change, and light can be confined as designed. The performance degradation of the waveguide 22 does not occur.
- the microbumps are not formed immediately below or in the vicinity of the optical waveguide 22 and are separated from the optical waveguide 22. Therefore, even if there is laser light which is not coupled to the optical waveguide 22 among infrared light emitted from the semiconductor laser 3, the laser light does not hit the microbumps, and the wavelength conversion element 20 is adversely affected. Absent.
- FIG. 3 is a top view of the optical device 1 shown in FIG.
- the wavelength conversion element 20 is shown in transmission for the purpose of making the structure easy to understand.
- An elongated optical waveguide 22 is disposed in the longitudinal direction substantially at the center of the wavelength conversion element 20, and the microbump 30a as a first joint and the microbump as a second joint are disposed with the optical waveguide 22 interposed therebetween.
- 30b are disposed side by side in the longitudinal direction of the wavelength conversion element 20.
- the micro bumps 30a and 30b are, for example, 4 .mu.m in diameter and 2.5 .mu.m in height, are formed at intervals of 10 .mu.m or 25 .mu.m, and are arranged evenly on the left and right of the optical waveguide 22.
- the diameter of the bumps is preferably 2 to 10 ⁇ m
- the height of the bumps is preferably 1 to 5 ⁇ m
- the pitch of the bumps is preferably 5 to 30 ⁇ m.
- the gaps 26 around the left, right, and lower surfaces of the optical waveguide 22 formed by the microbump structure are formed to cover the entire region in the longitudinal direction of the optical waveguide 22 as shown in FIG. 26, see FIG. 1).
- light is confined in the entire region in the longitudinal direction of the optical waveguide 22 by the difference in refractive index between the optical waveguide 22 and the air layer due to the gap 26, infrared light from the semiconductor laser 3 is received, and the inside of the optical waveguide 22 is The wavelength conversion is performed, and the laser beam L1 can be emitted to the optical fiber 5 from the emission port 22b.
- FIG. 4 is a diagram for explaining a micro bump bonding method.
- FIG. 4A is a schematic perspective view illustrating that the silicon substrate 10 and the wavelength conversion element 20 are bonded by the microbumps.
- FIG. 4B is a schematic side view illustrating that the silicon substrate 10 and the wavelength conversion element 20 are joined by the microbumps.
- a large number of cylindrical micro bumps 30 made of Au are formed on the Au film on the upper surface of the silicon substrate 10.
- an Au film 23 is formed on the lower surface of the wavelength conversion element 20, that is, the surface to be bonded to the silicon substrate 10.
- the surface of the micro bump 30 and the surface of the Au film 23 are activated.
- the micro bumps 30 are slightly deformed in the thickness direction according to the load, and the silicon substrate 10 and the wavelength conversion element 20 are bonded at normal temperature (normal temperature Activated junction).
- the room temperature activation bonding is performed because Au is activated.
- the manufacturing process can be simplified. Further, there is no concern that the silicon substrate 10 and the wavelength conversion element 20 will be misaligned due to heating, and the positional relationship between the silicon substrate 10 and the wavelength conversion element 20 can be maintained with high accuracy for bonding. Furthermore, since the Au micro bumps 30 have a thermal conductivity of about 320 W / (m ⁇ K) and heat is very easily transmitted, the heat from the wavelength conversion element 20 can be efficiently transferred to the silicon substrate 10. Therefore, the silicon substrate 10 can function as a heat sink of the wavelength conversion element 20.
- a gap 26m having an air layer is formed between the individual bumps.
- the gap 26m inside the micro bump 30 plays an important role as described later. Further, since the gap 26 between the optical waveguide 22 formed in the wavelength conversion element 20 and the silicon substrate 10 is secured by the micro bump structure (see FIG. 2), a groove for securing the gap on the silicon substrate 10 side The process of providing the silicon substrate 10 is not required, and the manufacturing process of the silicon substrate 10 can be simplified.
- FIG. 5 is a diagram for explaining alignment adjustment in the height direction by the microbumps.
- FIG. 5 is a schematic side view of the optical device 1 shown in FIG. 1 as viewed from the side.
- Micro bumps 30 for bonding the wavelength conversion element 20 are formed on the upper surface of the silicon substrate 10, micro bumps 33 for bonding the semiconductor laser 3 are formed, and micro bumps 34 for bonding the sub-substrate 4. Is formed.
- the micro bumps 30, 33 and 34 have the same form.
- the micro bumps 30, 33, 34 are formed on the surface of the silicon substrate 10, for example.
- a predetermined load K1 is applied to the semiconductor laser 3 while aligning the semiconductor laser 3 in the planar direction by means not shown, the thickness of the individual bumps in the microbumps 33 is deformed according to the load K1.
- the semiconductor laser 3 and the silicon substrate 10 are bonded.
- the bonded semiconductor laser 3 is driven to emit infrared light (not shown), and while the alignment of the wavelength conversion element 20 in the plane direction is performed in this state, a predetermined load K2 is applied to the wavelength conversion element 20 Is added little by little to bond to the silicon substrate 10 while deforming the thickness of the micro bumps 30.
- a predetermined load K2 is applied to the wavelength conversion element 20 Is added little by little to bond to the silicon substrate 10 while deforming the thickness of the micro bumps 30.
- infrared light from the semiconductor laser 3 is made incident on the optical waveguide 22 of the wavelength conversion element 20, and light emitted from the optical waveguide 22 is detected by a detector (not shown).
- a detector not shown
- a predetermined load K3 is gradually applied to the sub-substrate 4 to make the thickness of the micro bumps 34 It is bonded to the silicon substrate 10 while being deformed.
- the light emitted from the wavelength conversion element 20 is incident on the optical fiber 5 fixed by the sub-substrate 4, and the light emitted from the optical fiber 5 is detected by a detector (not shown).
- a detector not shown
- the semiconductor laser 3 mounted on the silicon substrate 10, the wavelength conversion element 20, and the optical fiber 5 fixed to the sub substrate 4 can be respectively aligned to realize an optical device optically coupled with high accuracy.
- alignment between elements is extremely important.
- the thickness of the microbumps can be changed by adjusting the load at the time of bonding the mounted components, so alignment adjustment in the height direction of the mounted components can be performed with high accuracy, and high accuracy between the elements Alignment can be easily realized.
- the optical device 1 can prevent stress on the wavelength conversion element 20 and the like, and thus has high reliability.
- FIG. 6 is a schematic enlarged top view of the optical device 1 for describing the flow of air in the vicinity of the optical waveguide.
- the wavelength conversion element 20 is shown as being transmitted for the sake of easy understanding of the structure, and parts other than the wavelength conversion element 20 are omitted.
- the optical waveguide 22 is disposed substantially at the center of the wavelength conversion element 20, the microbumps 30a and 30b are formed on the left and right of the optical waveguide 22 in the drawing, and the wavelength conversion element 20 includes the microbumps 30a. , 30b bond to the silicon substrate 10.
- the individual bumps of the microbumps 30a and 30b are arranged in a grid in the vertical and horizontal directions.
- the number of each bump of micro bump 30a, 30b shown in FIG. 6 is described in small numbers in order to make arrangement
- a gap 26 is formed around the optical waveguide 22, and an air layer 27 exists in the gap 26.
- a large number of very thin planar gaps 26m are formed on the microbumps 30a and 30b by the arrangement of the bumps, and the air layer 27 is also present in the gaps 26m inside the microbumps 30a and 30b.
- the ITO film 25 is formed on the entire lower surface of the wavelength conversion element 20 as described above, but is omitted in FIG.
- the ITO film 25 When electricity is supplied to the ITO film 25 (see FIG. 2) functioning as a heater via the micro bumps 30a and 30b, the ITO film 25 generates heat to heat the optical waveguide 22 and its periphery, but the periphery of the optical waveguide 22 is heated by heating.
- the air layer 27 present in the part expands. The expansion of the air layer 27 causes the pressure of the air layer 27 to rise. However, the air layer 27 passes through the many gaps 26 m inside the micro bumps 30 a and 30 b in the left and right direction as shown by the arrow B 1 and diffuses to the outside of the wavelength conversion element 20. Is kept almost constant.
- the heating by the ITO film 25 reaches a predetermined temperature
- the current supplied to the ITO film 25 is stopped by control means (not shown).
- the temperature of the optical waveguide 22 and its peripheral portion is It falls in a relatively short time.
- the air layer 27 has a flow path (arrow B1) by the gap 26m between the microbumps 30a and 30b. Therefore, the pressure of the air layer 27 is kept approximately constant. Therefore, stress can be prevented from being applied to the wavelength conversion element 20. As a result, generation of distortion of the wavelength conversion element 20 due to pressure change of the air layer 27 is prevented, and problems such as fluctuation of wavelength conversion characteristics and fluctuation of emitted light due to misalignment of the wavelength conversion element 20 are eliminated. Can realize an excellent optical device.
- the micro bumps 30a and 30b are composed of bumps having a very small thickness and a narrow distance, even if many gaps 26m inside the micro bumps are formed in a plane, the height is Thin and narrow. Therefore, dust of such a size as to cause a problem from the gap 26m between the micro bumps 30a and 30b can not penetrate. As a result, it is possible to prevent the characteristic variation of the wavelength conversion element due to the influence of the adhesion of dust and the like around the optical waveguide 22, and to provide a highly reliable optical device having stable characteristics for a long period of time.
- temperature control is performed to turn on and off the current to the ITO film 25 which is a heater while measuring the temperature so as to maintain the temperature at a predetermined temperature.
- the current to the ITO film 25 is turned on, the optical waveguide 22 and its peripheral portion are heated, and when the current is turned off, the optical waveguide 22 and its peripheral portion are cooled by the function of the silicon substrate 10 as a heat sink.
- the temperature of the optical waveguide 22 and its peripheral portion is maintained in an appropriate temperature range, it is possible to realize an optical device that outputs high-power and stable laser light.
- the arrangement of the micro bumps 30a and 30b shown in FIG. 6 is an arrangement in which the bumps are arranged in a grid in the longitudinal and lateral directions, the arrangement of the bumps is not limited to this.
- FIG. 7 is a view for explaining the flow of air by another arrangement of micro bumps.
- FIG. 7 (a) shows an example of the micro bumps 30a, 30b having a zigzag arrangement
- FIG. 7 (b) shows an example of the micro bumps 30a, 30 b having a random arrangement.
- the air layer 27 in the gap 26 around the optical waveguide 22 repeats expansion and contraction by turning the current to the ITO film 25 ON and OFF, but the air layers 27 are arranged in a row.
- a large number of gaps 26m of the micro bumps 30a and 30b are passed as indicated by the arrow B2. Therefore, the pressure of the air layer 27 in the gap 26 is kept substantially constant as the air layer 27 repeats diffusion to the outside and absorption from the outside. The flow of air in the case of absorption is opposite to the direction of the arrow B2.
- the air layer 27 in the gap 26 around the optical waveguide 22 repeats expansion and contraction by turning the current to the ITO film 25 ON and OFF, but the air layers 27 are microbumps arranged randomly.
- a number of gaps 26m of 30a, 30b are passed as shown by arrow B3. Therefore, the pressure of the air layer 27 in the gap 26 is kept substantially constant by repeating the diffusion to the outside and the absorption from the outside. The flow of air in the case of absorption is opposite to the direction of the arrow B3.
- the arrangement of the microbumps 30a and 30b is lattice-like, green-like, or random-like, provided that the microbumps have a predetermined thickness and a predetermined range of intervals, and the gaps 26m of the bumps are flowed through the air layer 27. It becomes a path
- the heater for adjusting the temperature of the wavelength conversion element 20 is configured by the ITO film 25 covering the entire lower surface of the wavelength conversion element 20, and the ITO film 25 as a heater is used as the wavelength conversion element 20. It is disposed close to the optical waveguide 22 to be formed. Therefore, the optical device 1 can perform temperature control (temperature management) efficiently and accurately. Further, in the optical device 1, since the micro bump structure is adopted for bonding, the groove on the silicon substrate 10 side is unnecessary, and the distortion of the wavelength conversion element 20 due to the pressure change and the dust on the optical waveguide 22 It prevents intrusion and is highly reliable.
- an InTiO film instead of the ITO film 25, an InTiO film may be used.
- the InTiO film is a film in which Ti is added to indium oxide.
- an ITO film is also applicable, but Is preferred. This is because the InTiO film has conductivity similar to that of the ITO film, and has higher transmittance and lower absorption than the ITO film in the long wavelength region.
- FIG. 8 is a cross-sectional view of another optical device 100.
- the outline of the entire configuration of the optical device 100 is the same as that of the optical device 1 shown in FIG. 1, and FIG. 8 shows a cross-sectional view of the optical device 100 at the same position as AA ′ shown in FIG.
- the same elements as those of the optical device 1 are denoted by the same reference numerals, and overlapping descriptions will be partially omitted.
- the wavelength conversion element 20 in FIG. 8 is a ridge type structure of SHG crystal whose main component is LiNbO 3.
- the optical waveguide 22 is formed in the protrusion 21c between the recesses 21a and 21b.
- the optical device 100 has a ridge-type wavelength conversion element mounted as an optical element, and a heater for adjusting the temperature of the wavelength conversion element is formed of an Au film on the lower surface of the wavelength conversion element excluding the periphery of the optical waveguide of the wavelength conversion element. ing.
- Thin Au films 40 and 41 are formed on the lower surface of the wavelength conversion element 20 across the optical waveguide 22, that is, on the flat portions 20 a and 20 b and partial regions of the concave portions 21 a and 21 b. A part of the Au films 40 and 41 is formed along the optical waveguide 22 and functions as a heater for heating the optical waveguide 22. The detailed pattern shape of the Au films 40 and 41 will be described later. The Au films 40 and 41 are not formed in the vicinity of the optical waveguide 22 but are arranged at a predetermined distance.
- the upper surface of the silicon substrate 10 is made of Au having a predetermined thickness and excellent conductivity as well as the optical device 1 at positions facing the flat portions 20 a and 20 b.
- Micro bumps 30a and 30b are respectively formed.
- the silicon substrate 10 and the wavelength conversion element 20 are activated at normal temperature by aligning and pressing the micro bumps 30 a and 30 b on the silicon substrate 10 and the Au films 40 and 41 of the flat portions 20 a and 20 b of the wavelength conversion element 20. Bond.
- a gap 26 by an air layer exists by the micro bumps 30a and 30b.
- the optical waveguide 22 located in the lower part of the wavelength conversion element 20 is not in contact with the silicon substrate 10 due to the gap 26, and the left and right and the lower surface of the optical waveguide 22 are covered with the air layer. Due to the presence of the gap 26, three surfaces on the left, right, and lower sides around the optical waveguide 22 become air layers, and light can be confined to the optical waveguide 22 using the difference in refractive index with the air layer around this.
- FIG. 9 is an enlarged top view of a part of the wavelength conversion element 20 of the optical device 100.
- the optical waveguide 22 is disposed in the longitudinal direction substantially at the center of the wavelength conversion element 20, and Au films 40 and 41 as heaters are formed on the lower surface of the wavelength conversion element 20 with the optical waveguide 22 interposed therebetween. It is done.
- the Au films 40 and 41 have heater portions 40a and 41a.
- the heater portions 40a and 41a are formed in a narrow linear shape so as to have a predetermined electrical resistance, sandwich the optical waveguide 22, and maintain the predetermined distance from the optical waveguide 22 along the longitudinal direction of the optical waveguide 22 It is done.
- the heater units 40a and 41a are connected to a plurality of lead-out units 40b and 41b connected at predetermined intervals, and the lead-out units 40b and 41b are connected to the electrodes 40c and 41c. That is, the Au films 40 and 41 are configured by the heater portions 40a and 41a, the plurality of lead portions 40b and 41b, and the plurality of electrodes 40c and 41c.
- the heater parts 40a and 41a of the Au films 40 and 41 are formed in the concave parts 21a and 21b of the wavelength conversion element 20, and the electrodes 40c and 41c are formed in the flat parts 20a and 20b. , 41b are formed from the concave portions 21a, 21b to the flat portions 20a, 20b.
- 8 is a cross-sectional view showing a cross section along substantially the center of one of the lead-out portions 40b and 41b shown in FIG.
- Micro bumps 30 a and 30 b are formed on the silicon substrate 10 facing the respective electrodes 40 c and 41 c.
- the wavelength conversion element 20 and the silicon substrate 10 are pressurized, the wavelength conversion element 20 and the silicon substrate 10 are joined at room temperature activation, and mechanically, electrically, and thermally coupled Do.
- a predetermined voltage is supplied from the silicon substrate 10 to the plurality of electrodes 40c and 41c via the microbumps 30a and 30b, a current flows to the heater portions 40a and 41a to generate heat, and the optical waveguide 22 and its Temperature can be adjusted by heating the surroundings.
- a voltage V1 is applied between two electrodes 40c shown in FIG. 9 and a different voltage V2 is applied between the other electrodes 40c.
- the electric resistance of the heater unit 40a to which the voltage V1 is applied is R1
- the electric resistance of the heater unit 40a to which the voltage V2 is applied is R2.
- the temperature is adjusted to be high because it is easily influenced by the outside air, and in the block of the optical waveguide 22 near the center of the optical device, the temperature is adjusted to be lower Fine temperature control can be performed according to the external environment.
- the heater 40a on the left side of the optical waveguide 22 in the drawing has been described above, different voltages are similarly applied between the electrodes 41c for the heater 41a on the right of the drawing to adjust the temperature for each block. can do. It is preferable that the temperature adjustment be performed simultaneously for both the left and right heater parts 40a and 41a, but the temperature adjustment may be performed separately for the left and right as necessary.
- the optical device 100 although a plurality of electrodes are provided for one heater unit and temperature adjustment can be performed for each block, it is not limited to this configuration. For example, only at both ends of the heater unit By providing an electrode and applying a predetermined voltage, a simple control may be performed to collectively adjust the temperature of the entire heater unit.
- the heaters for heating the optical waveguide 22 are formed of the Au films 40 and 41, the lower surface of the wavelength conversion element 20 is bonded to the microbumps 30a and 30b on the silicon substrate 10 side.
- the manufacturing process of the wavelength conversion element 20 can be simplified by the optical device 1 in which the Au film is formed on the surface of the ITO film.
- the heater portions 40a and 41a of the Au films 40 and 41 are formed along the longitudinal direction of the optical waveguide 22, heat generation from the heater portions 40a and 41a is efficiently transmitted to the optical waveguide 22 and its peripheral portion There is also an advantage that can be done.
- the micro bump structure is used to form the gap 26 (see FIG. 8) between the wavelength conversion element 20 and the silicon substrate 10. There is an advantage that it is not necessary to set up etc. Further, in the optical device 100, similarly to the optical device 1, there is also an advantage that the flow path of the air layer around the optical waveguide 22 is secured, and the stress on the optical waveguide 22 can be prevented. Furthermore, in the optical device 100, as in the optical device 1, the microbumps have a structure in which a large number of very thin narrow gaps are formed. There is also an advantage that can be prevented.
- the ITO film used in the optical device 1 may be used instead of the Au films 40 and 41 functioning as a heater.
- Au films 23 a and 23 b are formed on the surface of the flat portions 20 a and 20 b of the wavelength conversion element 20 on which the ITO film is formed. It should be joined with 30b.
- FIG. 10 is a cross-sectional view of still another optical device 110.
- the outline of the overall configuration of the optical device 110 is the same as that of the optical device 1 shown in FIG. 1, and FIG. 10 shows a cross-sectional view of the optical device 110 at the same position as AA ′ shown in FIG.
- the same elements as those of the optical device 1 are denoted by the same reference numerals, and overlapping descriptions will be partially omitted.
- the wavelength conversion element 20 in FIG. 10 is a ridge type structure of SHG crystal whose main component is LiNbO 3.
- the optical waveguide 22 is formed in the protrusion 21c between the recesses 21a and 21b. Since the optical waveguide 22 is formed in the convex portion 21c between the two concave portions 21a and 21b, the three surfaces around the optical waveguide 22 become air layers, and light is transmitted using the refractive index difference from the surrounding air layers. It can be closed.
- Au films 23 a and 23 b are formed on the two plane portions 20 a and 20 b other than the concave portions 21 a and 21 b in the lower part of the wavelength conversion element 20.
- the optical device 110 mounts a ridge type wavelength conversion element as an optical element, and a heater for adjusting the temperature of the wavelength conversion element is mounted on the side of the silicon substrate to be joined to the wavelength conversion element.
- micro bumps 30 a and 30 b made of Au having excellent conductivity and thermal conductivity are provided at positions facing the flat portions 20 a and 20 b of the wavelength conversion element 20 on the upper surface of the silicon substrate 10. Each is formed. As a result, the micro bumps 30 a and 30 b on the silicon substrate 10 and the Au films 23 a and 23 b on the lower surface of the wavelength conversion element 20 are activated at room temperature to bond the silicon substrate 10 and the wavelength conversion element 20.
- heaters 50a and 50b which are temperature adjusting means of the wavelength conversion element 20, are formed.
- the micro bumps 30a and 30b are formed close to the top of the heaters 50a and 50b, respectively. Therefore, the heaters 50 a and 50 b and the micro bumps 30 a and 30 b are disposed with the optical waveguide 22 of the wavelength conversion element 20 interposed therebetween.
- the heaters 50 a and 50 b and the microbumps 30 a and 30 b are not formed immediately below the optical waveguide 22, but are formed in a region away from immediately below the optical waveguide 22.
- the heat generated when the heaters 50a, 50b are energized passes through the micro bumps 30a, 30b excellent in thermal conductivity, and the optical waveguide of the wavelength conversion element 20 by the route indicated by the arrow C1. It is transmitted to the vicinity of 22. Therefore, the heat generated by energizing the heaters 50a and 50b can efficiently heat the optical waveguide 22 and adjust its temperature.
- the details of the micro bumps 30a and 30b and the heaters 50a and 50b will be described later.
- FIG. 11 is a top view schematically showing the silicon substrate 10 and the wavelength conversion element 20 of the optical device 110 shown in FIG.
- the semiconductor laser 3, the sub-substrate 4, the micro bumps 30a and 30b, and the like are omitted, and they are described as perspective views so that the positional relationship between the silicon substrate 10 and the wavelength conversion element 20 becomes clear.
- the optical waveguide 22 is formed from one end to the other end in the longitudinal direction of the wavelength conversion element 20, and in the drawing, the laser of the harmonic wave from the emission port 22b of the end of the upper optical waveguide 22 Light L1 is emitted.
- the two rows of heaters 50 a and 50 b are formed along the left and right sides of the optical waveguide 22 so as to sandwich the optical waveguide 22 in the vicinity of the optical waveguide 22.
- the entire optical waveguide 22 can be uniformly heated by the heaters 50a and 50b, and the temperature can be adjusted.
- the heaters 50a and 50b are connected in parallel by the wiring patterns 50c and 50d, and are connected to the electrodes 50e and 50f on the silicon substrate 10. By applying a voltage to the electrodes 50e and 50f from the outside to supply a predetermined current, the heaters 50a and 50b can be heated to adjust the temperature of the optical waveguide 22 of the wavelength conversion element 20.
- the optical device 110 two rows of heaters 50a and 50b are provided on the side of the silicon substrate 10 with the optical waveguide 22 in between, and the Au micro bumps 30a and 30b are disposed above the heaters 50a and 50b. Therefore, the heat generated by the heaters 50a and 50b of the silicon substrate 10 can be efficiently transmitted to the optical waveguide 22 through the microbumps 30a and 30b, and the temperature adjustment of the wavelength conversion element 20 can be performed.
- the microbumps 30a, 30b and the heaters 50a, 50b are formed immediately below the flat portions 20a, 20b of the wavelength conversion element 20, and the microbumps and the heaters are formed directly below the optical waveguide 22.
- the heater driving circuit for driving the heaters 50a and 50b is built in the silicon substrate 10, the electrodes 50e and 50f connected to the outside are unnecessary, and both ends of the heaters 50a and 50b are built-in heaters. It will be connected to the drive circuit.
- the silicon substrate 10 can incorporate not only the heater drive circuit but also a circuit for driving the semiconductor laser 3 (see FIG. 2) and various other circuits.
- the optical device 110 forms the heater for adjusting the temperature of the wavelength conversion element 20 in the vicinity of the surface of the silicon substrate 10, there is no need to form the heater on the wavelength conversion element 20 side.
- the manufacturing process of the wavelength conversion element 20 can be simplified.
- the heaters 50a and 50b formed on the silicon substrate 10 can be formed by a semiconductor process for manufacturing the silicon substrate 10, there is no need to add a new manufacturing process for the heater, and an optical device can be efficiently manufactured. Can.
- the gap 26 (see FIG. 10) is formed between the wavelength conversion element 20 and the silicon substrate 10, the groove is formed in the silicon substrate 10.
- the wavelength conversion element of the ridge type structure is shown as an example, the wavelength conversion element is not limited to the ridge type, and for example, a wavelength conversion element by proton exchange method or It may be an embedded type wavelength conversion element. Further, the optical element is not limited to the wavelength conversion element, and may be an optical element having another function.
- the heater for adjusting the temperature of the wavelength conversion element 20 may be provided on both the wavelength conversion element side and the silicon substrate side.
- optical devices 1, 100 and 110 described above can be widely used in various fields such as laser projectors, illumination devices using laser light, and optical tweezers as short wavelength laser light sources such as blue and green.
- FIG. 12 is a diagram schematically showing the overall configuration of another optical device 200.
- the optical device 200 includes a plate-like silicon substrate 207, a wavelength conversion element 201 as an optical element bonded onto the silicon substrate 207, and a semiconductor laser 203 for emitting laser light. .
- the optical device 200 is supported by a metal member 204 which is a package material. Here, for convenience, it is shown as a plate-shaped metal member 204.
- the metal member 204 fixes the silicon substrate 207 to mechanically protect the entire optical device 200, and also has a function as a heat dissipation means of the optical device 200.
- the semiconductor laser 203 emits a fundamental wave (not shown) of infrared light when supplied with a drive current from the silicon substrate 207 by means not shown.
- the wavelength conversion element 201 receives infrared light from the semiconductor laser 203 into the waveguide 201a (indicated by a broken line), converts the light into harmonic light inside the waveguide 201a, and converts the green or blue laser light L1. The light is emitted from the exit 1 b of the waveguide 22.
- the semiconductor laser 203 oscillates infrared light with a wavelength of 1064 nm, and the wavelength conversion element 201 converts it into green laser light with a wavelength of 532 nm.
- the semiconductor laser 203 oscillates infrared light with a wavelength of 860 nm, and the wavelength conversion element 201 converts it into blue laser light with a wavelength of 430 nm.
- the optical device 200 shown in FIG. 12 can be used for a light source device such as a small projector using a laser beam as a light source.
- FIG. 13 is a plan view of the optical device 200
- FIG. 14 is a cross-sectional view taken along the line D-D 'of FIG.
- the metal member 204 is abbreviate
- FIG. 15 is a plan view of the wavelength conversion element 201, which corresponds to the plan view of the optical device 200 of FIG.
- FIG. 16 is an enlarged view of a connection portion between the heater and the lead-out portion.
- FIG. 17 is a plan view of the silicon substrate 207. As shown in FIG. FIG. 17 corresponds to the plan view of the optical device 200 of FIG.
- the wavelength conversion element 201 is, for example, a proton exchange type wavelength conversion element of SHG crystal whose main component is LiNbO 3. As shown in FIG. 13 to FIG. 15, a waveguide 201a is formed at the approximate center of the lower part of the wavelength conversion element 201 by a proton exchange method. A strip-shaped heater 202 is formed at a location along the longitudinal direction of the waveguide 201 a via an SiO 2 film or the like.
- the transparent conductive film forming the heater 202 is made of an indium oxide (ITO) film.
- ITO indium oxide
- InTiO may be used as the transparent conductive film for forming the heater 202.
- the InTiO film is a film in which Ti is added to indium oxide.
- an ITO film is also applicable. It is more preferable to use an InTiO film. This is because the InTiO film can be made to have a higher transmittance and a lower absorptivity than the ITO film in a long wavelength region while maintaining the same conductivity as the ITO film.
- a plurality of lead-out portions 205 for applying a voltage to the heater 202 are formed at predetermined intervals with respect to the strip-like heater 202 using the same material as the heater 202.
- the heater 202 is configured to be thin so as to have high resistance in order to function as a heater, and the lead-out portion 205 is configured so as to be lower in resistance than the heater 202.
- At least three lead-out portions 205 are provided.
- the connecting portion with the heater 202 is thin and is formed so as to become thicker as it goes away from the heater 202. This is to secure a large number of high-resistance regions functioning as the heater of the heater 202.
- the heater 202 and the lead-out portion 205 can be simultaneously formed by patterning a transparent conductive film such as indium oxide (ITO).
- the waveguide 202a can be uniformly formed without dividing the heater 202. Therefore, the optical influence of the heater 202 on the waveguide 201a can be suppressed.
- an Au film 223 is formed so as to overlap with the lead-out portion 205 formed in the wavelength conversion element 201.
- the Au film 223 is a metal film for bonding to a micro bump 230 formed on a silicon substrate 207 described later.
- an electrode pattern 206 is formed on the silicon substrate 207 at a position corresponding to the Au film 223 formed on the wavelength conversion element 201.
- micro bumps 230 for bonding to the Au film 223 of the wavelength conversion element 201 are formed.
- terminals Ta and Tb for electrical connection with the outside are formed.
- the terminals Ta and Tb are electrically connected to the heater 202 through the micro bumps 230, the Au film 223, and the lead-out portion 25, and a voltage can be applied to the heater 202 from the terminals Ta and Tb.
- the optical device 200 shown in FIGS. 12 to 17 shows an example in which the heater 202 and the lead-out portion 205 are provided for the wavelength conversion element 201 having a proton exchange type waveguide.
- the heater 202 and the lead-out portion 205 as shown in FIG. 13 to FIG. 15 for a wavelength conversion element having a ridge type waveguide.
- FIG. 18 is a diagram for explaining micro bump bonding.
- FIG. 18 (a) is a perspective view for explaining that the silicon substrate 207 and the wavelength conversion element 201 are bonded by the micro bumps 330
- FIG. 18 (b) is a silicon substrate 207 and the wavelength conversion element 201.
- FIG. 6 is a side view illustrating bonding by micro bumps 330.
- a large number of cylindrical micro bumps 330 made of Au are formed on an Au thin film.
- an Au thin film 223 is formed on the lower surface of the wavelength conversion element 201, that is, the surface to be bonded to the silicon substrate 207.
- Au is activated and the silicon substrate 207 and the wavelength conversion element 201 are bonded at normal temperature (normal temperature activation bonding).
- the diameter of the micro bump 330 is about 5 ⁇ m, and the height is about 1 ⁇ m.
- the manufacturing process can be simplified. Further, the silicon substrate 207 and the wavelength conversion element 201 do not have to be displaced due to heating, and the silicon substrate 207 and the wavelength conversion element 201 can be joined with high accuracy.
- FIG. 19 is an explanatory view showing a part of the configuration of the light device 209. As shown in FIG. FIG. 19 shows an electrically equivalent circuit of the heater 202 of the wavelength conversion element 201, the lead-out portion 205, and the terminals Ta and Tb.
- the optical device 209 includes an optical device 200 and voltage application means 208 for applying a voltage to the terminals Ta and Tb.
- the heater 202 is divided into regions of resistors R, the lead-out portions 205 are connected to both ends of each resistor R, and terminals Ta and Tb are provided at the ends of the respective lead-out portions 205.
- the Joule heat due to the current flowing through each resistor R of the heater 202 by the voltage applied to each terminal Ta, Tb, partial temperature control of the waveguide by the heater 202 becomes possible.
- FIG. 20 is an explanatory view showing an example of application of a voltage to each of the terminals Ta and Tb.
- the same voltage Vx is applied to the terminals Tb1 to T5 located alternately, and different voltages V1 to V4 are applied to the remaining terminals Ta1 to T4, respectively, from the two resistors R
- Different currents I1 to I4 can be supplied to the following areas (AREA) 1 to 4, respectively.
- temperature control can be performed independently in the areas (AREA) 1-4.
- FIG. 21 is a diagram showing an example of control of the heater 202 by the voltage application means 208.
- FIG. 21A shows an example of control in the case where there is no phase difference between the voltage applied to the terminal Ta and the voltage applied to the terminal Tb
- FIG. 21B shows the voltage applied to the terminal Ta and the terminal Tb
- 21 (c) shows the case where the voltage applied to the terminal Ta and the voltage applied to the terminal Tb have a phase difference (2).
- FIG. The control zero shown in FIG. 21 is so-called pulse width modulation control, and a rectangular wave voltage having the same amplitude and period is applied to the terminal Ta and the terminal Tb.
- the voltage application means 208 controls each control voltage terminal (a rectangular wave phase shifted with reference to the rectangular wave applied to the common electrode (Tb in the example of FIG. 20) by a pulse width modulation control method.
- the configuration is added to Ta).
- analog (peak value) control it becomes possible to easily realize precise temperature control by digital control with multiple bits of, for example, 10 bits or more using only a simple digital circuit.
- the optical device provided with the voltage application means to the optical device may be called an optical device.
- FIG. 22 is a plan view of the wavelength conversion element 301 in still another optical device 300
- FIG. 23 is a cross-sectional view of the wavelength conversion element 301 shown in FIG. 22 and 23 show only a part of the wavelength conversion element 301 in the optical device 300, and the other configuration is the same as the optical device 200 described above.
- the wavelength conversion element 301 is provided with a first electrode 310a made of Au and a second electrode 310b.
- lead portions 301a made of the same Au are provided toward the waveguide 301a.
- a heater 302a made of Au is provided in parallel along the waveguide 301a.
- a lead portion 301b made of the same Au is provided toward the waveguide 301a.
- a heater 302 b made of Au is provided in parallel along the waveguide 301 a.
- the waveguide 301a is provided in the convex portion of the ridge.
- the heaters 302a and 302b can be disposed close to the waveguide 301a to extend the lead portions 301a and 301b to the positions of the recessed portions on both sides of the ridge portion, and the heaters 302a and 302b directly heat the waveguide 301a. It became possible.
- the waveguide 301a may be provided in a portion other than the ridge structure portion.
- the first electrode 310a, the second electrode 310b, the lead portions 301a and 301b, and the heaters 302a and 302b are formed in the wavelength conversion element 301 using the same material (for example, Au). There is.
- the first electrode 310a and the second electrode 310b are also used as a metal film for bonding to the micro bumps 230 formed on the silicon substrate 207 shown in FIG.
- the heater is formed of the same material as the electrode (metal film) to be joined, the electrodes of the heaters 302a and 302b do not need to be drawn separately.
- the size of the pattern can be adjusted to have a resistance value suitable for pulse width modulation control such as 5 V, for example.
- a resistance value suitable for pulse width modulation control such as 5 V, for example.
- the resistance ratio ⁇ of Au 2. 35 ⁇ 10 ⁇ 8 ⁇ m
- L 1 ⁇ 10 ⁇ 3 m
- A 2 ⁇ 0.5 ⁇ 10 ⁇ 12 m 2.
- the length W of the lead portions 301 a and 301 b may be about 2 mm.
- FIG. 24 is a view showing a modification of the wavelength conversion element 301 shown in FIG.
- FIG. 24 shows a wavelength conversion element 301 ′ which is a modified example in which the electrode 305 for polarization inversion is provided in the wavelength conversion element 301 shown in FIG.
- the electrode 305 for polarization inversion is not provided over the entire width of the wavelength conversion element 301 ′, but a portion (a predetermined width corresponding to the ridge portion of the waveguide 301a It is provided only in W1).
- the electrode 305 for polarization inversion is formed of an ITO film.
- the first substrate 308 c and the second substrate 308 d that constitute the wavelength conversion element 301 ′ are bonded by the adhesive layer 306. The presence of the adhesive layer 306 between the waveguide 301a and the electrode 305 can reduce the heat conduction at the portion of the electrode 305 for polarization inversion by the ITO film.
- FIG. 25A is a view for explaining a detection method of a heater applied voltage
- FIG. 25B is a view for explaining another detection method of the heater applied voltage.
- Temperature control can be performed in blocks using the plurality of first electrodes 310 a and the second electrodes 310 b illustrated in FIG. In this case, the applied voltage between the electrodes can be accurately detected by the general four-terminal method as shown in FIG.
- the plurality of first electrodes 310a will be described as an example.
- FIG. 25A shows the case where the applied voltage of the heater 302a2 (R2) is detected.
- the current I is supplied from the electrodes 310a1 and 310a4 on both sides of the pair of electrodes 310a2 and 310a3, and the voltage V between the pair of electrodes 310a2 and 310a3 of the heater 302a2 is detected.
- FIG. 25B shows the case where the applied voltage of the heater 302a3 (R3) is detected.
- the current I is supplied from the electrodes 310a2 and 310a5 on both sides of the pair of electrodes 310a3 and 310a4, and the voltage V between the pair of electrodes 310a3 and 310a4 of the heater 302a3 is detected.
- the heater structure and heater control method of the optical device 300 and the modified example of the optical device 300 shown in FIGS. 22 to 25 may be applied to the optical devices 1, 100 and 110 described above.
- the optical device provided with the voltage application means to the optical device may be called an optical device.
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Abstract
Description
御を容易に実現することが可能となる。
図1に示す様に、光デバイス1は、板状のシリコン基板10と、シリコン基板10上に接合される光素子としての波長変換素子20、シリコン基板10上に接合されレーザ光を出射する半導体レーザ3、及びシリコン基板10上に接合され光ファイバ5を固定するブ基板4等から構成される。光デバイス1は、光素子としてリッジ型波長変換素子を搭載し、温度特性補正手段として波長変換素子の温度調整を行うヒータが、波長変換素子の下面全体を覆うITO膜によって構成されている。
している。したがって、光デバイス1では、光導波路22にマイクロバンプが直接接触していないので、光導波路22と周囲との屈折率差が変化することがなく、設計通りに光を閉じ込めることができるので、光導波路22の性能低下は生じない。
が加わらず、波長変換効率が低下する恐れはない。さらに、マイクロバンプは光導波路22の直下や近傍に形成されず光導波路22から離れている。したがって、半導体レーザ3から出射される赤外光のうち、光導波路22に結合しなかったレーザ光があっても、レーザ光がマイクロバンプに当たることがなく、波長変換素子20に悪影響を及ぼすことはない。
バンプ34の厚みを変形させながらシリコン基板10に接合する。このとき、波長変換素子20からの出射光をサブ基板4で固定された光ファイバ5に入射し、光ファイバ5からの出射光を図示しない検出器で検出し、出射光が最大となる位置まで荷重を加えることで、波長変換素子20と光ファイバ5との間の調芯を行う。
いので温度を高めに調整し、光デバイスの中心付近の光導波路22のブロックでは、温度
を低めに調整するなど、外部環境に応じた細かい温度制御を行うことができる。なお、上記では、光導波路22の図面上左側のヒータ部40aについて述べたが、図面上右側のヒータ部41aについても、同様に各電極41c間に異なる電圧を印加して、ブロックごとに温度調整することができる。この温度調整は、左右のヒータ部40a、41aの両方を同時に行うことが好ましいが、必要に応じて左右別々に温度調整しても良い。
22の直下にはマイクロバンプとヒータを配置しない構成を採用している。この理由
は、光デバイス1で説明した光導波路22の直下にマイクロバンプを配置しない理由と同様であるので、ここでの説明は省略する。
されるため、シリコン基板10に溝等を設ける必要がない利点がある。また、光デバイス110では、光デバイス1と同様に、光導波路22の周囲の空気層の流通経路が確保されて、光導波路22にストレスが加わることを防ぐことができる利点もある。さらに、光デバイス110では、光デバイス1と同様に、マイクロバンプは非常に薄く狭い隙間が多数形成される構造であるので、ゴミ等の進入を防いで光導波路22の周辺にゴミが付着するのを防止できる利点もある。
温度調整するヒータは、波長変換素子側とシリコン基板側の両方に設けても良い。
図12に示すように、光デバイス200は、板状のシリコン基板207と、シリコン基板207上に接合される光素子としての波長変換素子201及びレーザ光を出射する半導体レーザ203等から構成される。
図19は、波長変換素子201のヒータ202、引き出し部205及び端子Ta、Tbの電気的な等価回路を示している。光装置209は、光デバイス200と、端子Ta、Tbに対して電圧を印加する電圧印加手段208とを備えている。
図20に示すように、一つおきに位置する端子Tb1~5に同一の電圧Vxを印加し、残りの端子Ta1~4にそれぞれ異なる電圧V1~V4を印加することにより、2つの抵抗Rからなる領域(AREA)1~4に対して、それぞれ異なる電流I1~I4を流すことができる。これにより、領域(AREA)1~4において、独立して温度制御を行うことが可能となる。
相差がない場合(td=0)、ヒータ202の抵抗Rの両端に電位差(Vd)は生じず、抵抗Rに電流は流れないため熱エネルギーは発生しない。また、図21(b)に示すように、端子Taに印加する電圧と端子Tbに印加する電圧とに位相差tdが、0<td<T/2である場合、ヒータ202の抵抗Rに電位差(Vd)に応じた電流が流れることにより発生する熱エネルギーは、P=V2/R x 2td/Tとなる。
Claims (9)
- 光デバイスであって、
基板と、
前記基板と向かい合う面に形成された光導波路を有する光素子と、
前記光導波路を挟んで位置するように前記基板上に形成された接合部と、
前記光導波路を加熱するために、前記光素子又は前記基板の少なくとも一方に形成されたヒータと、
金属材料から構成されたマイクロバンプ構造と、を有し、
前記光導波路と前記基板との間に隙間が形成されるように、前記マイクロバンプ構造を介して前記接合部と前記光素子とが接合されている、
ことを特徴とする光デバイス。 - 前記マイクロバンプ構造は、前記光導波路と前記基板との間に形成された前記隙間に対して、空気の出し入れが可能な隙間を有している、請求項1に記載の光デバイス。
- 前記ヒータは、前記光素子の前記基板と向かい合う面に形成されている、請求項1又は2に記載の光デバイス。
- 前記マイクロバンプ構造はAuから構成されて、前記接合部上に形成され、
前記光素子は、前記マイクロバンプ構造と接合するためのAu膜を有する、
請求項1~3の何れか一項に記載の光デバイス。 - 前記マイクロバンプ構造は、高さ1~5μmで直径2~10μmの円柱状の突起が5~30μmの間隔で形成されている、請求項1~4の何れか一項に記載の光デバイス。
- 前記ヒータは、ITO膜又はInTiO膜から構成される、請求項1~5の何れか一項に記載の光デバイス。
- 前記ヒータは、前記光導波路の長手方向に沿って帯状に形成され、
前記ヒータに電圧を印加するため、前記ヒータの長手方向に所定の間隔で設けられた引き出し部を更に有する、請求項1~6の何れか一項に記載の光デバイス。 - 前記引き出し部は、前記ヒータから離れるに従って太く形成される接続部を有している、請求項7に記載の光デバイス。
- 前記引き出し部にパルス幅変調方式の電圧を印加するための電圧印加手段を更に有する、請求項8に記載の光デバイス。
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US11209673B2 (en) * | 2019-10-30 | 2021-12-28 | Taiwan Semiconductor Manufacturing Company, Ltd. | Heater structure configured to improve thermal efficiency in a modulator device |
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