Composite substrate and method for producing composite substrate

Abstract

The present invention provides a composite substrate which is excellent in terms of the reflection characteristics of a wavelength conversion layer interface. This composite substrate has: a wavelength conversion layer that converts incident light into light which has a different wavelength; and a multilayer film that is disposed adjacent to the wavelength conversion layer. The multilayer film includes a plurality of refractive index layers. A region in which the abundance of inert gas atoms is 0.5 atom% or more is formed at an end part of the wavelength conversion layer in the thickness direction, the end part being on the side where the multilayer film is disposed. The abundance of inert gas atoms in a first refractive index layer of the multilayer film is less than 0.5 atom%, the first refractive index layer being positioned closest to the wavelength conversion layer.

Description

Composite substrate and method for manufacturing the same

[0001] The present invention relates to a composite substrate and a method for manufacturing the composite substrate.

[0002] Solid-state lasers capable of outputting short pulsed light are widely used. Lasers with extremely high optical output power at shorter pulse widths are expected to be applied in various fields such as sensing, precision machining, and medicine. As such a laser, for example, as disclosed in Patent Document 1, a laser structure has been proposed that combines a semiconductor laser, a solid-state laser gain medium layer that can function as a wavelength conversion layer, and a saturable absorber.

[0003] International Publication No. 2020 / 166420

[0004] In the above laser structure, the light reflection characteristics at the interface of the wavelength conversion layer can significantly affect the performance of the laser.

[0005] The present invention has been made in view of the above, and a main object of the present invention is to provide a composite substrate having excellent reflection characteristics at the interface of the wavelength conversion layer.

[0006] 1. A composite substrate according to an embodiment of the present invention includes a wavelength conversion layer that converts incident light into light of a different wavelength, and a multilayer film disposed adjacent to the wavelength conversion layer, the multilayer film including a plurality of refractive index layers, and a region having an abundance of inert gas atoms of 0.5 atomic % or more formed at a thickness-direction end of the wavelength conversion layer on the side where the multilayer film is disposed, and the abundance of inert gas atoms in a first refractive index layer of the multilayer film located closest to the wavelength conversion layer is less than 0.5 atomic %. 2. In the multilayer film of the composite substrate described in 1 above, the refractive indexes of the plurality of refractive index layers included in the multilayer film may each be 1.3 to 2.4, and the multilayer film may include one or more refractive index layers having a refractive index of 2.1 or more. 3. In the composite substrate described in 1 or 2 above, the wavelength conversion layer and the first refractive index layer may be bonded. 4. In the composite substrate described in any one of 1 to 3 above, the inert gas atoms may be argon or xenon. 5. In the multilayer film of the composite substrate described in any one of 1 to 4 above, the difference in refractive index between the layer with the highest refractive index and the layer with the lowest refractive index may be 0.5 or more. 6. In the composite substrate described in any one of 1 to 5 above, the wavelength conversion layer may be selected from a doped yttrium aluminum garnet crystal, a doped yttrium vanadate crystal, and a doped yttrium lithium fluoride crystal. 7. In the composite substrate described in any one of 1 to 6 above, the materials constituting each refractive index layer included in the multilayer film may be selected from silicon oxide, tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, cerium oxide, tungsten oxide, zinc oxide, niobium oxide, and magnesium oxide. 8. In the composite substrate described in any one of 1 to 7 above, the material constituting the first refractive index layer may be selected from tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, cerium oxide, tungsten oxide, zinc oxide, niobium oxide and magnesium oxide.9. In the composite substrate described in any one of 1 to 8 above, the thickness direction end of the wavelength conversion layer may include, in order from the multilayer film side, a third layer, a second layer, and a first layer, and the amount of inert gas atoms present in the second layer may be greater than the amount of inert gas atoms present in the third layer. 10. In the composite substrate described in any one of 1 to 10 above, the third layer may be an amorphous layer. 11. In the composite substrate described in any one of 1 to 10 above, the first refractive index layer may have a uniform refractive index in the thickness direction. 12. In the composite substrate described in any one of 1 to 11 above, the refractive indexes of two adjacent refractive index layers included in the multilayer film may be different. 13. In the composite substrate described in any one of 1 to 12 above, the thickness of each refractive index layer included in the multilayer film may be 50 nm or more and 300 nm or less. 14. The composite substrate described in any one of 1 to 13 above may include the wavelength conversion layer, the multilayer film, and a surface-emitting laser substrate, in this order. 15. The composite substrate described in any one of 1 to 14 above may have the wavelength conversion layer, the multilayer film, and a saturable absorbing layer, in this order. 16. A composite substrate according to another embodiment of the present invention has a surface-emitting laser substrate, a wavelength conversion layer that converts incident light into light of a different wavelength, and a saturable absorbing layer, in this order, and a multilayer film arranged adjacent to the wavelength conversion layer at least one of between the surface-emitting laser substrate and the wavelength conversion layer and between the saturable absorbing layer and the wavelength conversion layer, the multilayer film including a plurality of refractive index layers, a region having an abundance of inert gas atoms of 0.5 atomic % or more formed at an end of the wavelength conversion layer on the side where the multilayer film is arranged in the thickness direction, and the abundance of inert gas atoms in a first refractive index layer of the multilayer film located closest to the wavelength conversion layer is less than 0.5 atomic %. 17. A laser structure according to an embodiment of the present invention includes the composite substrate described in any one of 1 to 16 above.

[0007] 18. A method for manufacturing a composite substrate according to an embodiment of the present invention is the method for manufacturing a composite substrate described in any one of 1 to 17 above, and includes, in this order: preparing a laminated structure of a plurality of refractive index layers; performing an activation treatment on each of the surface of the wavelength converting material substrate and the surface of the laminated structure; performing a sputtering treatment on the surface of the wavelength converting material substrate to form a deposition layer containing components that constitute the wavelength converting material substrate on the surface of the laminated structure; and bonding the laminated structure to the wavelength converting material substrate. 19. In the method for manufacturing a composite substrate described in 18 above, the sputtering treatment may be performed for 3 to 10 minutes.

[0008] According to an embodiment of the present invention, a composite substrate having excellent reflection characteristics at the interface of the wavelength conversion layer can be provided.

[0009] 3B is a schematic cross-sectional view showing an outline of a configuration of a composite substrate according to one embodiment of the present invention; FIG. 3C is a schematic partially enlarged cross-sectional view showing an example of a state of an end portion in a thickness direction of a wavelength conversion layer; FIG. 3D is a diagram showing an example of a manufacturing process for a composite substrate according to one embodiment; FIG. 3E is a diagram continuing from FIG. 3A; FIG. 3F is a diagram continuing from FIG. 3C; FIG. 3G is a graph showing a simulation result of the reflection characteristics of a multilayer film of Example 1; FIG. 3G is a graph showing a simulation result of the reflection characteristics of a multilayer film of Comparative Example 1; FIG. 3H is a graph showing a simulation result of the reflection characteristics of a multilayer film of Example 2; FIG. 3I is a graph showing a simulation result of the reflection characteristics of a multilayer film of Example 4; FIG. 3J is a graph showing a simulation result of the reflection characteristics of a multilayer film of Example 5; FIG. 3L is a graph showing a simulation result of the reflection characteristics of a multilayer film of Example 6; FIG. 3L is a graph showing a simulation result of the reflection characteristics of a multilayer film of Example 7;

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In order to clarify the description, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in the drawings, the same or equivalent elements are given the same reference numerals, and redundant explanations may be omitted.

[0011] [Composite Substrate] Fig. 1 is a schematic cross-sectional view showing the general configuration of a composite substrate according to one embodiment of the present invention. Note that hatching of some components is omitted in Fig. 1 to make the drawing easier to see.

[0012] The composite substrate 100 has a first main surface 1 and a second main surface 2 facing each other, and includes a wavelength conversion layer 10 that converts incident light into light of a different wavelength, a first multilayer film 21 arranged adjacent to the first main surface 1 of the wavelength conversion layer 10, a second multilayer film 22 arranged adjacent to the second main surface 2 of the wavelength conversion layer 10, a substrate 30 arranged on the first multilayer film 21 side of the wavelength conversion layer 10, and a functional layer 40 arranged on the second multilayer film 22 side of the wavelength conversion layer 10.

[0013] The composite substrate 100 can be applied to, for example, a laser device. The substrate 30 is, for example, a substrate constituting a surface-emitting laser (e.g., a vertical-cavity surface-emitting laser (VCSEL) or a vertical-external-cavity surface-emitting laser (VECSEL)). For example, the wavelength conversion layer 10 can convert a first wavelength of laser light incident on the first main surface 1 side into a second wavelength. Although not shown, the substrate 30 can be provided with a resonator structure.

[0014] The substrate that constitutes the surface-emitting laser may be, for example, a gallium arsenide substrate, an indium phosphide substrate, or a gallium nitride substrate. The thickness of the substrate that constitutes the surface-emitting laser is, for example, 100 μm to 1000 μm.

[0015] The wavelength conversion layer 10 is made of any suitable wavelength conversion material capable of converting incident light into light of a different wavelength. A typical material for the wavelength conversion layer 10 is doped yttrium aluminum garnet (hereinafter referred to as YAG) crystal. Specific examples of doped YAG crystal include Yb ３＋ YAG crystal doped with Nd (Yb:YAG), ３＋ Other materials that can be used to form the wavelength conversion layer 10 include, for example, doped yttrium vanadate (hereinafter, referred to as YVO ４Doped YVO4 crystals are used. ４ Specific examples of crystals include Yb ３＋ Doped YVO ４ Crystal (Yb: YVO ４ ), Nd ３＋ Doped YVO ４ Crystal (Nd:YVO ４ ) Specific examples of doped YLF crystals include Yb ３＋ YLF crystal doped with Nd (Yb:YLF), ３＋ Doped YVO ４ Other examples of the material for the wavelength conversion layer 10 include Nd:glass, Yb:FAP, Yb:SFAP, Yb:glass, Yb:KYW, Yb:BCBF, Yb:YCOB, Yb:GdCOB, and Yb:YAB. Among these, examples of the material for the wavelength conversion layer 10 include doped YAG crystal and doped YVO ４ Preferably, a doped YLF crystal is used, which may exhibit, for example, comparable adhesion to adjacent layers. The thickness of the wavelength conversion layer 10 is, for example, 10 μm to 600 μm.

[0016] The first multilayer film 21 is a laminate of a plurality of refractive index layers. In the illustrated example, the first multilayer film 21 is formed by stacking the first refractive index layer 21 from the wavelength conversion layer 10 side. １ , second refractive index layer 21 ２ , third refractive index layer 21 ３ , ..., and the n-th refractive index layer 21 ｎ Specifically, the refractive index layer located closest to the wavelength conversion layer 10 is the first refractive index layer 21. １ The refractive index layer closest to the substrate 30 is the n-th refractive index layer 21 ｎ n is, for example, 10 to 50, and preferably 15 to 40. The thickness of each of the layers included in the first multilayer film 21 is, for example, 50 nm or more and 300 nm or less.

[0017] The first multilayer film 21 includes a plurality of refractive index layers having different refractive indices, including a high refractive index layer having a relatively high refractive index and a low refractive index layer having a relatively low refractive index. For example, two adjacent layers included in the first multilayer film 21 have different refractive indices, one being a high refractive index layer and the other being a low refractive index layer. Also, for example, at least a portion of the first multilayer film 21 may be configured by alternately stacking high refractive index layers and low refractive index layers. As a specific example, the second refractive index layer 21 ２ The refractive index of the first refractive index layer 21 １ and the third refractive index layer 21 ３ In this case, the refractive index of the first refractive index layer 21 may be smaller or larger than that of the first refractive index layer 21. １ and the third refractive index layer 21 ３ The refractive indexes of the first and second layers may be substantially the same or different.

[0018] The first multilayer film 21 is configured to transmit light of a first wavelength emitted from the substrate 30 side. Specifically, the first multilayer film 21 is configured to function as a transmission layer or an anti-reflection layer for light of the first wavelength. The first multilayer film 21 is configured to suppress emission of light of a second wavelength from the wavelength conversion layer 10 toward the substrate 30 side, for example, from the viewpoint of improving light utilization efficiency. Specifically, the first multilayer film 21 is configured to function as a reflective layer for light of the second wavelength. Such a function of the first multilayer film 21 can be realized, for example, by adjusting the number of refractive index layers (the above n) constituting the first multilayer film 21, the thickness of each refractive index layer, and the refractive index of each layer.

[0019] Laser light incident from the first main surface 1 (substrate 30) side can be emitted from the second main surface 2 side. For example, light of a second wavelength converted by the wavelength conversion layer 10 can be emitted after passing through the functional layer 40. The functional layer 40 can function as, for example, a saturable absorbing layer. In this case, the functional layer (saturable absorbing layer) 40 is typically made of Cr ４＋ YAG crystal doped with V (Cr:YAG), ３＋ The functional layer (saturable absorbing layer) 40 may be made of a material such as a YAG crystal (V:YAG) doped with V. The thickness of the functional layer (saturable absorbing layer) 40 is, for example, 10 μm to 600 μm.

[0020] The second multilayer film 22 is a laminate of a plurality of refractive index layers. In the illustrated example, the second multilayer film 22 is formed by stacking the first refractive index layer 22 from the wavelength conversion layer 10 side. １ , second refractive index layer 22 ２ , third refractive index layer 22 ３ , . . . and the n-th refractive index layer 22 ｎ Specifically, the layer located closest to the wavelength conversion layer 10 is the first refractive index layer 22 １ The layer closest to the functional layer 40 is the n-th refractive index layer 22 ｎ n is, for example, 10 to 50, and preferably 15 to 40. The thickness of each of the refractive index layers included in the second multilayer film 22 is, for example, 50 nm or more and 300 nm or less.

[0021] The second multilayer film 22 includes a plurality of refractive index layers having different refractive indices, including a high refractive index layer having a relatively high refractive index and a low refractive index layer having a relatively low refractive index. For example, two adjacent layers included in the second multilayer film 22 have different refractive indices, one being a high refractive index layer and the other being a low refractive index layer. Also, for example, at least a portion of the second multilayer film 22 may be configured by alternately stacking high refractive index layers and low refractive index layers. As a specific example, the second layer 22 ２ The refractive index of the first refractive index layer 22 １ and the third refractive index layer 22 ３ In this case, the refractive index of the first refractive index layer 22 may be smaller or larger than that of the first refractive index layer 22. １ and the third refractive index layer 22 ３ The refractive indexes of the first and second layers may be substantially the same or different.

[0022] The second multilayer film 22 is configured to transmit light of the second wavelength emitted from the wavelength conversion layer 10. Specifically, the second multilayer film 22 is configured to function as a transmission layer or an anti-reflection layer for light of the second wavelength. The second multilayer film 22 is configured to suppress emission of light of the first wavelength from the wavelength conversion layer 10 toward the functional layer 40, for example, from the viewpoint of improving light utilization efficiency. Specifically, the second multilayer film 22 is configured to function as a reflective layer for light of the first wavelength. Such a function of the second multilayer film 22 can be realized, for example, by adjusting the number of refractive index layers (the above n) constituting the second multilayer film 22, the thickness of each refractive index layer, and the refractive index of each refractive index layer.

[0023] As described above, each of the first multilayer film 21 and the second multilayer film 22 (hereinafter sometimes simply referred to as a multilayer film) is a laminate of multiple refractive index layers, and may include high-refractive index layers and low-refractive index layers with different refractive indices. The refractive index of each refractive index layer included in the multilayer film (the refractive index of the material constituting each refractive index layer included in the multilayer film) is, for example, 1.3 to 2.4, preferably 1.4 to 2.4, and more preferably 1.45 to 2.35. The refractive index may be a value measured using a spectroscopic ellipsometer or spectrophotometer. The refractive index of the high-refractive index layer is relatively higher than the refractive index of the low-refractive index layer. Specifically, the refractive index of the material constituting the high-refractive index layer is higher than the refractive index of the material constituting the low-refractive index layer. The refractive index of the low-refractive index layer is, for example, 1.3 to 1.8. The refractive index of the high-refractive index layer is, for example, 1.55 to 2.4.

[0024] The plurality of low refractive index layers that may be included in the multilayer film may each have the same configuration (e.g., material, thickness) or may have different configurations. Similarly, the plurality of high refractive index layers that may be included in the multilayer film may each have the same configuration (e.g., material, thickness) or may have different configurations.

[0025] The multilayer film preferably includes one or more refractive index layers having a refractive index of 2.1 or more. By including such a refractive index layer, desired transmission characteristics (reflection characteristics) can be favorably achieved. In the multilayer film, the difference in refractive index between the layer having the highest refractive index and the layer having the lowest refractive index is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more. From the viewpoint of satisfying such a difference, the multilayer film preferably includes one or more refractive index layers having a refractive index of 1.5 or less.

[0026] Dielectric materials are typically used as materials for forming each refractive index layer included in the multilayer film. Specific examples of materials for forming each refractive index layer included in the multilayer film include silicon oxide, tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, cerium oxide, tungsten oxide, zinc oxide, niobium oxide, and magnesium oxide. These may be used alone or in combination of two or more (for example, as a composite oxide). Specifically, the refractive index layer may be composed of an oxide containing at least one selected from silicon, tantalum, titanium, aluminum, yttrium, zirconium, hafnium, lanthanum, cerium, tungsten, zinc, niobium, and magnesium.

[0027] Specific examples of materials constituting the first refractive index layer included in the multilayer film include tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, cerium oxide, tungsten oxide, zinc oxide, niobium oxide, and magnesium oxide. These may be used alone or in combination of two or more (e.g., as a composite oxide). Specifically, the first refractive index layer may be composed of an oxide containing at least one selected from tantalum, titanium, aluminum, yttrium, zirconium, hafnium, lanthanum, cerium, tungsten, zinc, niobium, and magnesium. Such a first refractive index layer can provide excellent adhesion between the multilayer film and the wavelength conversion layer 10.

[0028] Each refractive index layer included in the multilayer film can be formed by any suitable method, such as sputtering, physical vapor deposition such as ion beam assisted deposition (IAD), chemical vapor deposition, or atomic layer deposition (ALD).

[0029] Inert gas atoms are present at the end 10a of the wavelength conversion layer 10 on the side where the multilayer film is disposed (hereinafter, sometimes referred to as the thickness direction end). Here, the thickness direction end refers to a portion having a certain thickness. Typical examples of inert gas atoms include argon and xenon. The region where inert gas atoms are present, formed at the thickness direction end 10a of the wavelength conversion layer 10, may be formed over the entire surface of the wavelength conversion layer 10. For example, the wavelength conversion layer 10 has a layer where inert gas atoms are present formed at the thickness direction end 10a. The abundance of inert gas atoms in the region (layer) where inert gas atoms are present is, for example, 0.5 atomic % or more and 10 atomic % or less, and may be 0.7 atomic % or more.

[0030] On the other hand, it is preferable that substantially no inert gas atoms are present in the thickness direction central portion 10b of the wavelength conversion layer 10. The amount of inert gas atoms present in the thickness direction central portion 10b of the wavelength conversion layer 10 is, for example, less than 0.5 atomic %, and may be 0.4 atomic % or less.

[0031] 2 is a schematic, partially enlarged cross-sectional view showing an example of the state of an end portion of the wavelength conversion layer in the thickness direction. At the end portion 10a of the wavelength conversion layer 10 in the thickness direction, a third layer 13, a second layer 12, and a first layer 11 are formed in this order from the multilayer film 21 (22) side. For example, the third layer 13 may be an amorphous layer. The first layer 11 may be a crystalline layer. The second layer 12 may be an amorphous layer, a crystalline layer, or a combination thereof. The second layer 12 and the third layer 13 may contain the constituent atoms of the first layer 11.

[0032] The inert gas atoms may be present mainly in the second layer 12. The inert gas atoms may be present in the third layer 13, or may be substantially absent in the third layer 13. For example, the abundance of inert gas atoms in the second layer 12 is greater than the abundance of inert gas atoms in the third layer 13. The abundance of inert gas atoms in the second layer 12 is, for example, 0.5 atomic % or more and 10 atomic % or less, and preferably 0.7 atomic % or more and 4 atomic % or less. The lower limit of the abundance of inert gas atoms in the third layer 13 may be 0.2 atomic %, and preferably 0 atomic %. The upper limit of the abundance of inert gas atoms in the third layer 13 may be 10 atomic %, and preferably 3 atomic %. The second layer 12 and / or the third layer 13 may contain Fe and / or Cr.

[0033] The thickness of the second layer 12 is, for example, 0.2 nm or more, and may be 0.4 nm or more. On the other hand, the thickness of the second layer 12 is, for example, 10 nm or less, and preferably 5 nm or less. The thickness of the third layer 13 is, for example, 0.2 nm or more, and may be 0.3 nm or more. On the other hand, the thickness of the third layer 13 is, for example, 8 nm or less, and preferably 4 nm or less.

[0034] The first refractive index layer of the multilayer film adjacent to the wavelength conversion layer 10 is substantially free of inert gas atoms, and the amount of inert gas atoms present in the first refractive index layer is, for example, less than 0.5 atomic %, and may be 0.4 atomic % or less. By having such a configuration for the first refractive index layer closest to the wavelength conversion layer 10, for example, the incorporation of components constituting the wavelength conversion layer into the first refractive index layer is suppressed, and the first refractive index layer can have a uniform refractive index in its thickness direction. Specifically, the first refractive index layer has substantially no difference in refractive index between the wavelength conversion layer 10 side and the second refractive index layer side in its thickness direction. The uniform refractive index of the first refractive index layer can, for example, satisfies desired reflection characteristics.

[0035] The abundance of the inert gas atoms can be determined by, for example, composition analysis using energy dispersive X-ray spectroscopy (EDX).

[0036] The composite substrate 100 may omit the functional layer 40 and the second multilayer film 22, or may omit the substrate 30 and the first multilayer film 21. Although not shown, the composite substrate 100 may further include any layer. The type, function, number, combination, arrangement, etc. of such layers may be appropriately set depending on the purpose. For example, the composite substrate 100 may have another functional layer (e.g., an optical scanner layer) provided on the functional layer 40.

[0037] The composite substrate 100 can be manufactured in any suitable shape. In one embodiment, it can be manufactured in the form of a wafer. The size of the composite substrate 100 can be appropriately set depending on the purpose. For example, the diameter of the wafer is 50 mm to 150 mm. Also, for example, the diameter of the wafer is 3 inches to 6 inches.

[0038] [Manufacturing Method] The composite substrate can be obtained by, for example, preparing a laminated structure of a plurality of refractive index layers and bonding this laminated structure to a wavelength converting material substrate.

[0039] 3A to 3D are diagrams showing an example of a manufacturing process for a composite substrate according to one embodiment. １ to the n-th refractive index layer 21 ｎ The nth layer is the nth refractive index layer 21 ｎ 1 shows a state in which films are formed in this order, forming an n-layer stack structure 20 on a substrate 30.

[0040] Next, the laminated structure 20 is directly bonded to the wavelength converting material substrate 14. When directly bonding, the laminated structure 20 and the wavelength converting material substrate 14 are preferably activated by any appropriate activation treatment.

[0041] The activation process is typically performed by irradiating a neutralizing beam. Preferably, a neutralizing beam is generated using an apparatus such as that described in JP 2014-086400 A, and the activation process is performed by irradiating this beam. Specifically, a saddlefield fast atom beam (FAB) source is used as the beam source, an inert gas such as argon or xenon is introduced into the chamber, and a high voltage is applied to the electrodes from a DC power supply. This generates a saddlefield electric field between the electrode (positive electrode) and the housing (negative electrode), causing electrons to move and generating a beam of atoms and ions from the inert gas. Of the beams that reach the grid, the ion beam is neutralized by the grid, and a beam of neutral atoms is emitted from the fast atom beam source. The voltage during beam irradiation is preferably 0.5 kV to 2.0 kV. The current during beam irradiation is preferably 50 mA to 200 mA.

[0042] In one embodiment, the activation treatment can be performed in two stages. Fig. 3B shows a state in which the first activation treatment is performed on the surface 20a of the laminate structure 20 and the surface 14a of the wavelength converting material substrate 14, respectively. Typically, the activation of the surface 20a of the laminate structure 20 and the activation of the surface 14a of the wavelength converting material substrate 14 can be performed simultaneously. The time for the first activation treatment (e.g., the irradiation time of the beam) is preferably 10 to 30 seconds.

[0043] FIG. 3C shows the second activation process. In the second activation process, the surface 14a of the wavelength converting material substrate 14 is further irradiated with a beam. Here, the stacked structure 20 is not substantially irradiated with a beam. The second activation process can form a deposition layer 15 containing components constituting the wavelength converting material substrate 14 on the surface of the stacked structure 20. Therefore, the second activation process can be considered a sputtering process. For example, the second activation process (sputtering process) is performed by irradiating the stacked structure 20 and the wavelength converting material substrate 14 with a beam in the first activation process, stopping the beam irradiation on the stacked structure 20, and continuing the beam irradiation on the wavelength converting material substrate 14 for a further predetermined time. The duration of the second activation process (sputtering process) (e.g., beam irradiation time) is, for example, 3 to 10 minutes, preferably 4 to 7 minutes.

[0044] The deposition layer 15 may be an amorphous layer. The thickness of the deposition layer 15 is preferably 0.2 nm to 8 nm, more preferably 0.3 nm to 4 nm. As described above, the deposition layer 15 may contain the components that make up the wavelength converting material substrate 14. The deposition layer 15 may also contain inert gas atoms. The deposition layer 15 may correspond to the third layer 13 of the resulting composite substrate.

[0045] After the activation treatment, the deposition layer 15 formed on the laminated structure 20 and the wavelength converting material substrate 14 are brought into contact with each other and pressurized to directly bond them together. In this way, a bonded body (composite substrate) 102 shown in FIG. 3D is obtained. The contact and pressurization are preferably carried out in a vacuum atmosphere. The temperature at this time is typically room temperature. Specifically, the temperature is preferably 20°C or higher and 40°C or lower, and more preferably 25°C or higher and 30°C or lower. The pressure applied is preferably 100N to 20,000N.

[0046] The dashed line in FIG. 3D indicates the bonding interface. The bonding interface may be located inside the wavelength conversion layer 10. The wavelength conversion layer 10 has three layers (a first layer 11, a second layer 12, and a third layer 13) formed near the bonding interface. The first layer 11, for example, does not substantially contain inert gas atoms used in the activation treatment. The second layer 12 is located closer to the first multilayer film 21 than the first layer 11 and may contain inert gas atoms. The third layer 13 is in contact with the first multilayer film 21 and may or may not contain inert gas atoms. The amounts of inert gas present in these layers are as described above. The first layer 11 may be composed of a crystalline wavelength converting material. The third layer 13 may be an amorphous layer in which the wavelength converting material has been amorphized. The second layer 12 may be composed of a crystalline wavelength converting material, an amorphous wavelength converting material, or a combination thereof.

[0047] By positioning the bonding interface within the wavelength conversion layer 10, the influence of the activation process on the laminate structure 20, which may require highly precise control of the refractive index, can be significantly reduced. Specifically, the first refractive index layer (the outermost layer of the laminate structure 20) of the multilayer film is substantially free of inert gas atoms used in the activation process, thereby suppressing the incorporation of wavelength conversion materials and the generation of amorphous structures (e.g., amorphous regions containing inert gas atoms) due to the activation process. As a result, the first refractive index layer can have a desired refractive index, and, for example, the multilayer film as a whole can satisfactorily achieve the desired reflection characteristics. Furthermore, the incorporation of impurities (e.g., Fe, Cr, etc., constituting the jig or base of the activation processing device) into the first refractive index layer (the outermost layer of the laminate structure 20) of the multilayer film can be suppressed. Impurities can affect, for example, the transmittance of the multilayer film. Furthermore, the generation of an amorphous layer due to bonding can be suppressed. Specifically, the thickness of the amorphous layer generated due to bonding can be reduced.

[0048] After direct bonding, the bonded body 102 may be subjected to an annealing treatment. Specifically, the bonded body 102 may be heated. The annealing treatment may diffuse and volatilize the inert gas atoms and the impurities. Furthermore, the annealing treatment may be expected to crystallize the amorphous state, and, for example, further improve the reflection characteristics. The temperature (heating temperature) of the annealing treatment may be, for example, 300°C to 450°C.

[0049] When bonding, the surfaces of the laminate structure 20 and the wavelength converting material substrate 14 are preferably flat. Specifically, the arithmetic mean roughness Ra of the surfaces of the laminate structure 20 and the wavelength converting material substrate 14 is preferably 5 nm or less, more preferably 2 nm or less, even more preferably 1 nm or less, and particularly preferably 0.3 nm or less. Examples of methods for flattening the surfaces include mirror polishing by chemical mechanical polishing (CMP), lap polishing, etc.

[0050] During the film formation and bonding, it is preferable to clean the surface of each layer, for example, to remove abrasive residue. Examples of cleaning methods include wet cleaning, dry cleaning, and scrub cleaning. Among these, scrub cleaning is preferred because it allows for simple and efficient cleaning. A specific example of scrub cleaning is a method in which a cleaning agent (e.g., the Sun Wash series manufactured by Lion Corporation) is used, followed by cleaning with a scrub cleaner using a solvent (e.g., a mixed solution of acetone and isopropyl alcohol (IPA)).

[0051] 3 shows the production of a bonded body of the wavelength converting layer 10 and the first multilayer film 21 by forming the layered structure 20 on the substrate 30. As in the example shown in FIG. 3, the layered structure 20 can be formed on the functional layer 40 and then bonded to the wavelength converting material substrate 14 to obtain a bonded body of the wavelength converting layer 10 and the second multilayer film 22. When obtaining the composite substrate shown in FIG. 1, the order in which the substrate 30 and the functional layer 40 are stacked on the wavelength converting material substrate 14 is not particularly limited. Specifically, the functional layer 40 may be bonded to the wavelength converting material substrate 14 after the substrate 30 has been bonded, or the functional layer 40 may be bonded to the wavelength converting material substrate 14 before the substrate 30 has been bonded.

[0052] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0053] [Example 1] A tantalum oxide (Ta ２ O ５ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were formed in the order and with the thicknesses shown in Table 1, forming a laminate structure of 29 refractive index layers in total. A Yb:YAG substrate was bonded to this laminate structure by the method shown in FIG. 3 to obtain a composite substrate. The refractive indexes of the layers are summarized in Table 1.

[0054] As shown in Table 1, the first refractive index layer (tantalum oxide layer) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0055] Comparative Example 1: A GaAs substrate was coated with tantalum oxide (Ta ２ O ５ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were formed in the same manner as in Example 1, forming a laminate structure of 29 refractive index layers in total. Then, a Yb:YAG substrate was bonded to this laminate structure in the same manner as in Example 1, except that the beam irradiation to the laminate structure was not stopped during the second activation treatment in the method shown in Figure 3, to obtain a composite substrate whose refractive indexes of the layers are summarized in Table 1.

[0056] As shown in Table 1, the activation treatment (beam irradiation) forms a layer (50 nm thick) on the Yb:YAG layer side of the first refractive index layer (tantalum oxide layer) with a refractive index lower than that of tantalum oxide (2.23). The constituent components of YAG can be confirmed in this layer (region).

[0057]

[0058] The simulation results of the reflection characteristics of the multilayer film of Example 1 are shown in FIG. 4, and the simulation results of the reflection characteristics of the multilayer film of Comparative Example 1 are shown in FIG.

[0059] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert it to light with a wavelength of 1030 nm. The multilayer films of Example 1 and Comparative Example 1 transmit light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppress the emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 1 had a reflectance of 0.1% at a wavelength of 940 nm, while the multilayer film of Comparative Example 1 had a reflectance of 1.5% at a wavelength of 940 nm. This indicates that the multilayer film of Example 1 can more effectively allow light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) to enter.

[0060] (Composition Analysis of Example 1) The 29th to 2nd refractive index layers shown in Table 1 were sequentially formed on a GaAs substrate with the materials and thicknesses shown in Table 1, and finally, a tantalum oxide layer (first refractive index layer) having a thickness of 200 nm was formed, forming a laminated structure of a total of 29 refractive index layers. Next, the surface of the Yb:YAG substrate (YAG crystal) and the surface (tantalum oxide layer side) of the GaAs substrate on which the laminated structure was formed were cleaned, and then both substrates were placed in a vacuum chamber and heated for 10 minutes. －６ The chamber was evacuated to the Pa range, and the surfaces of both substrates were simultaneously irradiated with Ar gas FAB (accelerating voltage 1 kV, Ar flow rate 27 sccm) for 15 seconds. The FAB irradiation on the GaAs substrate side was then stopped, and the FAB irradiation on the Yb:YAG substrate side was continued for another 285 seconds. The GaAs substrate and Yb:YAG substrate were then directly bonded. Specifically, the FAB-irradiated surfaces of the two substrates were overlapped and pressed at room temperature for 2 minutes at 10,000 N to bond the two substrates, resulting in a bonded structure as shown in Figures 2 and 3D. The resulting bonded structure was then subjected to an annealing treatment. Specifically, the resulting bonded structure was placed in a high-temperature furnace, and the temperature in the furnace was raised from room temperature to above 100°C, held for a certain period of time, and then returned to room temperature, thereby performing annealing.

[0061] In order to measure the Ar content (abundance) of each layer constituting the bonded structure, the bonded structure was thinned by a focused ion beam (FIB) method, while exposing the surface of each layer, and energy dispersive X-ray analysis (EDX) was performed. Specifically, analysis was performed by STEM-EDX observation using an atomic resolution analytical electron microscope (JEOL, JEM-ARM200F Dual-X) and an energy dispersive X-ray analyzer (JEOL, JED-2300) at an acceleration voltage of 200 kV and a beam spot size of approximately 0.2 nmΦ. The measurement results are shown below. The Ar content indicates the ratio of Ar atoms to all atoms present at the measurement point. Measurement point 1 (YAG crystal corresponding to the first layer 11): 0 atomic % Measurement point 2 (second layer 12): 2 atomic % Measurement point 3 (third layer 13): 1 atomic % Measurement point 4 (first refractive index layer 21 １ Tantalum oxide layer corresponding to

[0062] [Example 2] A tantalum oxide (Ta ２ O ５ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were deposited in the order and with the thicknesses shown in Table 2, forming a laminate structure of 33 refractive index layers in total. A Yb:YAG substrate was bonded to this laminate structure by the method shown in FIG. 3 to obtain a composite substrate. The refractive indexes of the layers are summarized in Table 2.

[0063]

[0064] As shown in Table 2, the first refractive index layer (tantalum oxide layer) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0065] The simulation results of the reflection characteristics of the multilayer film of Example 2 are shown in FIG.

[0066] The multilayer film of Example 2 can transmit light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer) and suppress the emission of light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer).

[0067] [Example 3] A titanium oxide (TiO ２ ) and zirconium oxide (ZrO ２ ) mixed crystal layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were deposited in the order and with the thicknesses shown in Table 3, forming a laminate structure of 29 refractive index layers in total, and a Yb:YAG substrate was bonded to this laminate structure by the method shown in Figure 3 to obtain a composite substrate whose refractive indexes of each layer are summarized in Table 3. The mixed crystal layer of titanium oxide and zirconium oxide can be formed in advance by sputtering using a target containing a mixed crystal of titanium oxide and zirconium oxide.

[0068]

[0069] As shown in Table 3, the first refractive index layer (a mixed crystal layer of titanium oxide and zirconium oxide) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0070] The simulation results of the reflection characteristics of the multilayer film of Example 3 are shown in FIG.

[0071] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert this to light with a wavelength of 1030 nm. The multilayer film of Example 3 transmits light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppresses the emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 3 had a reflectance of 0.1% at a wavelength of 940 nm.

[0072] [Example 4] A magnesium oxide (MgO) layer, a tantalum oxide (Ta) layer, and a GaAs substrate were deposited on the substrate. ２ O ５ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were deposited in the order and with the thicknesses shown in Table 4, forming a laminate structure of 29 refractive index layers in total. A Yb:YAG substrate was bonded to this laminate structure by the method shown in FIG. 3 to obtain a composite substrate. The refractive indexes of the layers are summarized in Table 4.

[0073]

[0074] As shown in Table 4, the first refractive index layer (magnesium oxide layer) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0075] The simulation results of the reflection characteristics of the multilayer film of Example 4 are shown in FIG.

[0076] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert it to light with a wavelength of 1030 nm. The multilayer film of Example 4 transmits light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppresses the emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 4 had a reflectance of 0.1% at a wavelength of 940 nm.

[0077] [Example 5] A substrate (GaAs substrate) was coated with titanium oxide (TiO ２ ) and zirconium oxide (ZrO ２ ) mixed crystal layer, tantalum oxide (Ta ２ O ５ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were formed in the order and with the thicknesses shown in Table 5, forming a laminate structure of 29 refractive index layers in total. A Yb:YAG substrate was bonded to this laminate structure by the method shown in FIG. 3 to obtain a composite substrate. The refractive indexes of the layers are summarized in Table 5.

[0078]

[0079] As shown in Table 5, the first refractive index layer (tantalum oxide layer) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0080] The simulation results of the reflection characteristics of the multilayer film of Example 5 are shown in FIG.

[0081] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert it to light with a wavelength of 1030 nm. The multilayer film of Example 5 transmits light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppresses emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 5 had a reflectance of 0.1% at a wavelength of 940 nm.

[0082] [Example 6] A titanium oxide (TiO ２ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３ ) layers were formed in the order and with the thicknesses shown in Table 6, forming a laminate structure of 29 refractive index layers in total. A Yb:YAG substrate was bonded to this laminate structure by the method shown in FIG. 3 to obtain a composite substrate. The refractive indexes of the layers are summarized in Table 6.

[0083]

[0084] As shown in Table 6, the first refractive index layer (titanium oxide layer) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0085] The simulation results of the reflection characteristics of the multilayer film of Example 6 are shown in FIG.

[0086] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert it to light with a wavelength of 1030 nm. The multilayer film of Example 6 transmits light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppresses the emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 6 had a reflectance of 0.1% at a wavelength of 940 nm.

[0087] [Example 7] A tantalum oxide (Ta ２ O ５ ) layer, silicon oxide (SiO ２ ) layer and aluminum oxide (Al ２ O ３) layers were formed in the order and with the thicknesses shown in Table 7, forming a laminate structure of 29 refractive index layers in total. A Yb:YAG substrate was bonded to this laminate structure by the method shown in FIG. 3 to obtain a composite substrate. The refractive indexes of the layers are summarized in Table 7.

[0088]

[0089] As shown in Table 7, the first refractive index layer (aluminum oxide layer) is significantly less affected by the activation treatment (beam irradiation), and a desired refractive index can be obtained.

[0090] The simulation results of the reflection characteristics of the multilayer film of Example 7 are shown in FIG.

[0091] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert it to light with a wavelength of 1030 nm. The multilayer film of Example 7 transmits light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppresses the emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 7 had a reflectance of 0.1% at a wavelength of 940 nm.

[0092] The composite substrate according to the embodiment of the present invention can be suitably used in laser devices for sensing, precision machining, medical applications, and the like.

[0093] REFERENCE SIGNS LIST 10 wavelength conversion layer 11 first layer 12 second layer 13 third layer 14 wavelength converting material substrate 20 laminated structure 21 first multilayer film 22 second multilayer film 30 substrate 40 functional layer 100 composite substrate 102 bonded body (composite substrate)

Claims

1. A composite substrate comprising: a wavelength conversion layer that converts incident light into light of a different wavelength; and a multilayer film disposed adjacent to the wavelength conversion layer, the multilayer film including a plurality of refractive index layers, a region having an abundance of inert gas atoms of 0.5 atomic % or more formed at an end in a thickness direction of the wavelength conversion layer on the side where the multilayer film is disposed, and an abundance of inert gas atoms in a first refractive index layer located closest to the wavelength conversion layer of the multilayer film being less than 0.5 atomic %.

2. The composite substrate according to claim 1, wherein the refractive index of each of the plurality of refractive index layers included in the multilayer film is 1.3 to 2.4, and the multilayer film includes at least one refractive index layer having a refractive index of 2.1 or more.

3. The composite substrate of claim 1, wherein the wavelength conversion layer and the first refractive index layer are bonded together.

4. The composite substrate according to claim 1, wherein the inert gas atoms are argon or xenon.

5. The composite substrate according to claim 1, wherein in said multi-layer film, the difference in refractive index between the layer having the highest refractive index and the layer having the lowest refractive index is 0.5 or more.

6. The composite substrate of claim 1, wherein the wavelength converting layer is selected from doped yttrium aluminum garnet crystals, doped yttrium vanadate crystals, and doped yttrium lithium fluoride crystals.

7. The composite substrate according to claim 1, wherein the materials constituting each refractive index layer included in the multilayer film are selected from silicon oxide, tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, cerium oxide, tungsten oxide, zinc oxide, niobium oxide and magnesium oxide.

8. The composite substrate of claim 1, wherein the material constituting the first refractive index layer is selected from tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, cerium oxide, tungsten oxide, zinc oxide, niobium oxide and magnesium oxide.

9. The composite substrate of claim 1, wherein an end portion of the wavelength conversion layer in a thickness direction includes, in order from the multilayer film side, a third layer, a second layer, and a first layer, and the amount of inert gas atoms in the second layer is greater than the amount of inert gas atoms in the third layer.

10. The composite substrate of claim 9, wherein the third layer is an amorphous layer.

11. The composite substrate according to claim 1, wherein the first refractive index layer has a uniform refractive index in the thickness direction.

12. The composite substrate according to claim 1, wherein the refractive indexes of two adjacent refractive index layers included in said multilayer film are different.

13. The composite substrate according to claim 1, wherein the thickness of each of the refractive index layers included in the multilayer film is 50 nm or more and 300 nm or less.

14. The composite substrate according to claim 1, comprising, in this order, the wavelength conversion layer, the multilayer film, and a surface emitting laser substrate.

15. The composite substrate according to claim 1, comprising, in this order, the wavelength conversion layer, the multilayer film, and a saturable absorbing layer.

16. A composite substrate comprising a surface-emitting laser substrate, a wavelength conversion layer that converts incident light into light of a different wavelength, and a saturable absorbing layer, in that order; and a multilayer film disposed adjacent to the wavelength conversion layer at least one of between the surface-emitting laser substrate and the wavelength conversion layer and between the saturable absorbing layer and the wavelength conversion layer, the multilayer film including a plurality of refractive index layers, a region having an abundance of inert gas atoms of 0.5 atomic % or more is formed at an end in the thickness direction of the wavelength conversion layer on the side where the multilayer film is disposed, and the abundance of inert gas atoms in a first refractive index layer located closest to the wavelength conversion layer of the multilayer film is less than 0.5 atomic %.

17. A laser structure comprising the composite substrate of claim 1.

18. A method for producing a composite substrate as described in claim 1, comprising, in this order: preparing a laminated structure of a plurality of refractive index layers; performing an activation treatment on each of a surface of the wavelength converting material substrate and a surface of the laminated structure; performing a sputtering treatment on the surface of the wavelength converting material substrate to form a deposition layer containing components that constitute the wavelength converting material substrate on the surface of the laminated structure; and bonding the laminated structure and the wavelength converting material substrate.

19. The method for producing a composite substrate according to claim 18, wherein the time for the sputtering process is 3 to 10 minutes.

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