Optical element, laser device, and method for manufacturing an optical element

Abstract

An optical element according to an embodiment comprises: a laser medium; a first intermediate layer provided on the laser medium; a first metal layer that is formed on the first intermediate layer and contains a Group 4 element or a Group 6 element; and a heat sink that is provided on the first metal layer and contains metal, the first intermediate layer being formed on the laser medium and including a dielectric multilayer film that totally reflects laser light generated or amplified by the laser medium, and the first intermediate layer being thicker than the penetration depth of an evanescent wave generated by reflection of light incident from the laser medium side by the dielectric multilayer film.

Description

Technical Field

[0001] The present invention relates to an optical element, a laser device, and a method for manufacturing an optical element.

Background Art

[0002] As technologies of an optical element including a laser medium and a laser device including the same, there are the technologies described in Patent Document 1, Patent Document 2, Non-Patent Document 1, Non-Patent Document 2, Non-Patent Document 3, Non-Patent Document 4, and Non-Patent Document 5.

[0003] For example, Non-Patent Document 2 discloses an optical element in which a heat sink is integrated with a laser medium and a total reflection film is provided between the laser medium and the heat sink.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

[0006] As described in Non-Patent Document 2, when the laser medium and heat sink are integrated, the heat generated in the laser medium is dissipated through the heat sink. Metals are used as heat sinks because they have a higher thermal conductivity than dielectrics. In Non-Patent Document 2, a total reflection film is provided between the laser medium and the heat sink. Therefore, the laser light generated or amplified using the laser medium is totally reflected by the total reflection film and output from the side opposite the heat sink when viewed from the laser medium. The total reflection film can function, for example, as part of an optical resonator. As described in Non-Patent Document 2, when the total reflection film and the heat sink are in contact and the heat sink is made of metal, the total reflection film and the metal are in contact. In such a configuration, if the output of the laser light is extremely high, the metal in contact with the total reflection film may be damaged, and as a result, the optical element including the laser medium, total reflection film, and metal heat sink may not be able to be used stably.

[0007] Therefore, the present invention aims to provide an optical element that can be used stably with high-power laser light, a laser device including the same, and a method for manufacturing the optical element. [Means for solving the problem]

[0008] The inventors of the present invention discovered that in a configuration in which a laser medium, a total reflection film, and a metal member are stacked in this order, the metal member is damaged by the evanescent waves generated when high-power laser light is incident on the total reflection film from the laser medium side, and this led to the present invention. Specifically, the inventors discovered that the evanescent waves generated by the total reflection of laser light by the total reflection film seep into the metal member, and a process occurs in which the metal member absorbs the evanescent waves, causing damage to the metal member, and this led to the present invention.

[0009] The optical element according to the present invention comprises a laser medium, a first intermediate layer provided on the laser medium, a first metal layer formed on the first intermediate layer and containing a group 4 or group 6 element, and a heat sink provided on the first metal layer and containing metal, wherein the first intermediate layer is formed on the laser medium and includes a dielectric multilayer film that totally reflects laser light generated or amplified by the laser medium, and the first intermediate layer is thicker than the seepage length of the evanescent wave generated by the reflection of light incident from the laser medium side by the dielectric multilayer film.

[0010] In the above configuration, a first intermediate layer and a first metal layer are arranged between the laser medium and the heat sink, from the laser medium side. The first intermediate layer is formed on the laser medium and includes a dielectric multilayer film that totally reflects the laser light generated or amplified by the laser medium. In the above configuration, the dielectric multilayer film of the first intermediate layer functions as a totally reflecting film. The first intermediate layer is thicker than the seepage length of the evanescent wave generated by the reflection of light incident from the laser medium side by the dielectric multilayer film. Therefore, even if high-power laser light is totally reflected by the dielectric multilayer film, the resulting evanescent wave is not absorbed by the first metal layer and the heat sink. As a result, the optical element can be used stably even with high-power laser light.

[0011] An optical element according to one embodiment may further have a second metal layer disposed between the first metal layer and the heat sink, and containing a group 10 element. In this case, the coefficient of linear expansion of the second metal layer containing the group 10 element is a value between the coefficient of linear expansion of the first metal layer and the coefficient of linear expansion of the heat sink. Therefore, even if the laser medium generates heat, the optical element is less likely to be damaged compared to the case without the second metal layer.

[0012] Examples of materials for the second metal layer mentioned above include nickel or platinum.

[0013] An optical element according to one embodiment may further have a second intermediate layer disposed between the first metal layer and the second metal layer. An example of the material of the intermediate layer is gold or a gold alloy.

[0014] Examples of the material of the first metal layer are chromium or titanium.

[0015] Examples of the material of the heat sink may be copper, copper tungsten, copper molybdenum, iron, aluminum, or an aluminum-silicon carbide composite.

[0016] The first intermediate layer may include the dielectric multilayer film and a non-metallic heat transfer layer disposed between the dielectric multilayer film and the first metal layer.

[0017] Examples of the material of the non-metallic heat transfer layer may be diamond, silicon carbide, or nitride.

[0018] The laser device according to another aspect of the present invention includes the optical element. Since this laser device includes the optical element, it is possible to stably output high-power laser light.

[0019] The method for manufacturing an optical element according to another aspect of the present invention includes a preparation step of preparing a first component including a laser medium and a second component including a heat sink containing a metal, and a bonding step of bonding the first component and the second component. The preparation step includes a step of forming a first intermediate layer on the laser medium and a step of forming a first metal layer containing a Group 4 element or a Group 6 element on the first intermediate layer. In the bonding step, the first component and the second component are bonded via the first metal layer. The first intermediate layer includes a dielectric multilayer film formed on the laser medium and totally reflecting laser light generated or amplified by the laser medium. In the step of forming the first intermediate layer, the first intermediate layer is formed such that the thickness of the first intermediate layer is greater than the penetration length of the evanescent wave generated by reflection of light incident from the laser medium side by the dielectric multilayer film.

[0020] In this manufacturing method, it is possible to manufacture an optical element in which a first intermediate layer and a first metal layer are arranged between a laser medium and a heat sink, starting from the laser medium side. The first metal layer contains a Group 4 element or a Group 6 element. In the optical element with the above configuration, the dielectric multilayer film of the first intermediate layer functions as a total reflection film. The above first intermediate layer is thicker than the penetration length of the evanescent wave generated by the reflection of the light incident from the laser medium side by the dielectric multilayer film. Therefore, even when high-power laser light is totally reflected by the dielectric multilayer film, the evanescent wave generated thereby is not absorbed by the first metal layer and the heat sink. Therefore, the optical element can be stably used even for high-power laser light. Therefore, in the above manufacturing method, an optical element that can be stably used even for high-power laser light can be manufactured.

[0021] The above preparation step includes a step of forming a second metal layer containing a Group 10 element on the above heat sink. In the above bonding step, the first component and the second component may be bonded via the first metal layer and the second metal layer. In this case, an optical element having a second metal layer between the first metal layer and the heat sink can be manufactured. The linear expansion coefficient of the second metal layer containing a Group 10 element is a value between the linear expansion coefficient of the first metal layer and the linear expansion coefficient of the heat sink. Therefore, even when the laser medium generates heat, the optical element is less likely to be damaged compared to the case where it does not have the second metal layer. That is, in the manufacturing method of an optical element having a step of forming a second metal layer containing a Group 10 element, an optical element that can be used more stably even for high-power laser light can be manufactured.

[0022] The above preparation step may include a step of forming a layer to be a second intermediate layer, which is arranged between the first metal layer and the second metal layer, on at least one of the first metal layer and the second metal layer.

[0023] In the above bonding step, after surface activating the surface of the first component on the bonding side with the second component and the surface of the second component on the bonding side with the first component, the surface-activated first component and the second component may be bonded. In this case, the first component and the second component can be directly and firmly bonded.

[0024] A method for manufacturing an optical element according to one embodiment further comprises a step of surface-activating the surface of the first component on the side that is joined to the second component and the surface of the second component on the side that is joined to the first component, the preparation step further comprises a step of forming a second metal layer containing a group 10 element on the first metal layer, the second component is the heat sink, and in the joining step, the first component and the second component may be joined via the second metal layer.

[0025] In this case, an optical element having a second metal layer between the first metal layer and the heat sink can be manufactured. The coefficient of linear expansion of the second metal layer containing a group 10 element is a value between the coefficient of linear expansion of the first metal layer and the coefficient of linear expansion of the heat sink. Therefore, even if the laser medium generates heat, the optical element is less likely to be damaged compared to the case without the second metal layer. In other words, a method for manufacturing an optical element that includes a step of forming a second metal layer containing a group 10 element can manufacture an optical element that can be used more stably even with high-power laser light. Surface activation treatment is applied to the surface of the first component that is joined to the second component and to the surface of the second component that is joined to the first component, so that the first component and the second component can be joined firmly and directly.

[0026] The step of forming the first intermediate layer may include the steps of forming the dielectric multilayer film on the laser medium and forming a nonmetallic heat transfer layer on the dielectric multilayer film. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide an optical element that can be used stably with high-power laser light, a laser device including the same, and a method for manufacturing the optical element. [Brief explanation of the drawing]

[0028] [Figure 1] Figure 1 is a diagram showing the schematic configuration of an optical element according to the first embodiment. [Figure 2]Figure 2 is a diagram illustrating an example of a manufacturing method for the optical element shown in Figure 1. [Figure 3] Figure 3 is a diagram illustrating another example of the manufacturing method for the optical element shown in Figure 1. [Figure 4] Figure 4 is a schematic diagram showing the general configuration of the optical element according to the second embodiment. [Figure 5] Figure 5 is a diagram illustrating an example of a manufacturing method for the optical element shown in Figure 4. [Figure 6] Figure 6 is a diagram illustrating another example of the manufacturing method for the optical element shown in Figure 4. [Figure 7] Figure 7 is a schematic diagram showing the general configuration of the optical element according to the third embodiment. [Figure 8] Figure 8 is a diagram illustrating an example of a manufacturing method for the optical element shown in Figure 7. [Figure 9] Figure 9 is a schematic diagram of an example of a laser device using optical elements. [Figure 10] Figure 10 is a schematic diagram showing another example of a laser device, which is a laser oscillator. [Figure 11] Figure 11 is a schematic diagram showing another example of a laser device, which is a laser oscillator. [Figure 12] Figure 12 is a schematic diagram showing another example of a laser device, which is a laser oscillator. [Figure 13] Figure 13 is a schematic diagram showing another example of a laser device using optical elements. [Figure 14] Figure 14 is a schematic diagram showing another example of a laser device as a laser amplifier. [Figure 15] Figure 15 is a schematic diagram of another example of a laser device using optical elements. [Figure 16] Figure 16 is a schematic diagram showing another example of a laser device as a laser regenerative amplifier. [Figure 17] Figure 17 is a schematic diagram showing another example of a laser device that is a laser regenerative amplifier. [Figure 18] Figure 18 is a schematic diagram showing another example of a laser device that is a laser regenerative amplifier. [Figure 19] Figure 19 is a schematic diagram showing the general configuration of another example of an optical element. [Figure 20] Figure 20 is a schematic diagram showing the general configuration of another example of an optical element. [Figure 21] Figure 21 is a schematic diagram showing the general configuration of another example of an optical element. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In the description of the drawings, the same reference numerals are used for identical or equivalent elements, and redundant descriptions are omitted. The dimensional ratios in the drawings do not necessarily correspond to those described.

[0030] (First Embodiment) Figure 1 is a diagram showing the schematic configuration of an optical element 10 according to one embodiment. The optical element 10 shown in Figure 1 comprises a laser medium 11, a dielectric multilayer film (first intermediate layer) 12, a first metal layer 13, and a heat sink 14. The optical element 10 is a laser medium with a heat sink that has a total internal reflection function due to the dielectric multilayer film 12. The optical element 10 is applied to laser oscillators, laser amplifiers, and the like. The optical element 10 may have an intermediate layer (second intermediate layer) 15. The optical element 10 may have a second metal layer 16. In the following, unless otherwise specified, embodiments having an intermediate layer 15 and a second metal layer 16 will be described.

[0031] The laser medium 11 is a material that, in its excited state, forms a population inversion where amplification exceeds loss, and amplifies light using stimulated emission. The laser medium 11 is an optical component for the oscillation or amplification of laser light L. The laser medium 11 is also called a gain medium.

[0032] Examples of materials for the laser medium 11 include optical gain materials formed from oxides doped with rare earth ions that act as light emission centers, optical gain materials formed from oxides doped with transition metal ions that act as light emission centers, optical gain materials formed from oxides that act as color centers, and optical gain materials formed from semiconductors.

[0033] Examples of rare earth ions include Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Examples of transition metal ions include Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. Examples of parent materials to which rare earth ions, transition metal ions, etc. are added include garnet-based materials such as YAG, YSAG, YGAG, YSGG, GGG, GSGG, and LuAG; fluoride-based materials such as YLF, LiSAF, LiCAF, MgF2, and CaF2; vanadate-based materials such as YVO4, GdVO4, and LuVO4; apatite-based materials such as FAP, sFAP, VAP, and sVAP; alumina-based materials such as Al2O3 and BeAl2O3; dioxide-based materials such as Y2O3, Sc2O3, and Lu2O3; and tungstate-based materials such as KGW and KYW. The laser medium 11 may be a single crystal, amorphous (including glass), or ceramic. The matrix material may be various amorphous glasses. Examples of semiconductors include GaAs, GaAlAs, GaAlP, GaP, GaN, InGaN, AlGaN, and GaAlN.

[0034] A dielectric multilayer film 12 is formed on the first surface 11a of the laser medium 11. The dielectric multilayer film 12 totally reflects the laser light L generated or amplified by stimulated emission of the laser medium 11. In one embodiment, the dielectric multilayer film 12 functions as an HR coating layer for the laser light L. The dielectric multilayer film 12 may reflect light of wavelengths other than the wavelength of the laser light L. The dielectric multilayer film 12 is constructed by alternately stacking a plurality of high refractive index layers and a plurality of low refractive index layers (layers having a refractive index smaller than that of the high refractive index layers). In the dielectric multilayer film 12, desired reflection characteristics can be achieved by adjusting the refractive index and thickness of each of the high refractive index layers and low refractive index layers. The dielectric multilayer film 12 has a thickness such that the evanescent wave EW generated when the laser light L undergoes total internal reflection does not reach the first metal layer 13. In other words, the thickness t of the dielectric multilayer film 12 is longer than the seepage length d of the evanescent wave EW. The dielectric multilayer film 12 is a multilayer film composed of multiple layers, for example, with wavelengths of 10 nm to 9000 nm (100 Å to 90000 Å). Therefore, an example of the thickness t of the dielectric multilayer film 12 is a few μm. Depending on the wavelength of light reflected by the dielectric multilayer film 12, the thickness t may be 10 μm or more. However, a thinner dielectric multilayer film 12 is preferable. The material of the layer closest to the first metal layer 13 in the dielectric multilayer film 12 is mainly suitable as Al2O3, which has high thermal conductivity, but SiO2 may also be used.

[0035] The first metal layer 13 is formed on the first surface 12a of the dielectric multilayer film 12. The first surface 12a is the surface of the dielectric multilayer film 12 opposite to the laser medium 11. The first metal layer 13 functions as a buffer layer when joining the laser medium 11 and the heat sink 14, which have different coefficients of thermal expansion. The first metal layer 13 contains a metallic material with a coefficient of thermal expansion close to that of the laser medium 11. The first metal layer 13 contains a group 4 element or a group 6 element. An example of a group 4 element is titanium (Ti), and an example of a group 6 element is chromium (Cr). An example of the thickness of the first metal layer 13 is between 1 nm and 900 nm (10 Å and 9000 Å). To prevent migration, which is a concern when temperature-increasing treatment is required, a Ni layer or Pt layer may be provided on the side of the first metal layer 13 opposite to the dielectric multilayer film 12. Examples of the thickness of the above Ni or Pt layers are between 10 nm and 900 nm (100 to 9000 Å).

[0036] The heat sink 14 is a heat transfer element for cooling the laser medium 11 and contains metal. The heat sink 14 is, for example, a metal heat sink. The material of the heat sink 14 is a material with high thermal conductivity. Examples of materials for the heat sink 14 include copper, copper alloys, aluminum, iron, aluminum-silicon carbide composites, etc. Examples of copper alloys include copper-tungsten and copper-molybdenum.

[0037] The intermediate layer 15 is formed on the first surface 13a of the first metal layer 13. The first surface 13a is the surface of the first metal layer 13 opposite to the dielectric multilayer film 12. The intermediate layer 15 also functions as a buffer layer. The material of the intermediate layer 15 is gold or a gold alloy. An example of the thickness of the intermediate layer 15 is between 5 nm and 10 μm.

[0038] The second metal layer 16 is formed on the first surface 15a of the intermediate layer 15. The first surface 15a is the surface of the intermediate layer 15 opposite to the first metal layer 13. In the arrangement shown in Figure 1, the second metal layer 16 is formed on the first surface 14a of the heat sink 14. The second metal layer 16 also functions as a buffer layer. The second metal layer 16 is formed from a material having a coefficient of thermal expansion close to (or between) that of the first metal layer 13 and the heat sink 14. The second metal layer 16 contains Group 10 elements. Examples of materials for the second metal layer 16 are nickel (Ni) or platinum (Pt). The thickness of the second metal layer 16 is, for example, 10 nm to 900 nm (100 Å to 9000 Å). If heating treatment is required, the thickness of the second metal layer 16 is, for example, about 0.1 μm to 10 μm.

[0039] A dielectric multilayer film 17 may be formed on the second surface 11b of the laser medium 11 of the optical element 10 to suppress the reflection of laser light L. The dielectric multilayer film 17 functions as an anti-reflective coating (AR coating) for laser light L.

[0040] An example of a manufacturing method for the optical element 10 will be explained using Figure 2. Figure 2 is a diagram illustrating an example of a manufacturing method for the optical element 10 shown in Figure 1. As shown in Figure 1, we will explain the case in which an optical element 10 having a dielectric multilayer film 12, a first metal layer 13, an intermediate layer 15, and a second metal layer 16 between a laser medium 11 and a heat sink 14 is manufactured.

[0041] When manufacturing the optical element 10, a first component 20 comprising a laser medium 11 and a second component 30 comprising a heat sink 14 are prepared (preparation step).

[0042] The preparation process includes a step of preparing the first part 20 and a step of preparing the second part 30. The order in which the steps of preparing the first part 20 and the second part 30 are performed is not limited.

[0043] In the process of preparing the first component 20, the following steps are performed in order: forming a dielectric multilayer film 12 on the laser medium 11, forming a first metal layer 13 on the dielectric multilayer film 12, and forming an intermediate layer 151 on the first metal layer 13. The dielectric multilayer film 12, the first metal layer 13, and the intermediate layer 151 can be formed by film deposition technology, thin-film technology, etc.

[0044] The conditions that the dielectric multilayer film 12 and the first metal layer 13 must satisfy are as described above, so we will omit further explanation. The intermediate layer 151 is a layer that constitutes the intermediate layer 15 shown in Figure 1 by being joined with the intermediate layer 152 of the second component 30, which will be described later. Therefore, the material of the intermediate layer 151 is the same as that of the intermediate layer 15. The thickness of the intermediate layer 151 is such that the sum of the thickness of the intermediate layer 151 and the thickness of the intermediate layer 152 corresponds to the thickness of the intermediate layer 15.

[0045] If the optical element 10 has a dielectric multilayer film 17, the step of preparing the first component 20 includes the step of forming the dielectric multilayer film 17.

[0046] In the process of preparing the second component 30, the steps of forming a second metal layer 16 on the heat sink 14 and forming an intermediate layer 152 on the second metal layer 16 are carried out in order. The second metal layer 16 and the intermediate layer 152 can be formed by film deposition technology, thin film technology, etc.

[0047] The conditions that the second metal layer 16 must satisfy are as described above, so we will omit further explanation. The intermediate layer 152 is a layer that constitutes the intermediate layer 15 shown in Figure 1 by being joined with the intermediate layer 151 of the first component 20 described above. Therefore, the material of the intermediate layer 152 is the same as that of the intermediate layer 15. The thickness of the intermediate layer 152 is such that the sum of the thickness of the intermediate layer 152 and the thickness of the intermediate layer 151 corresponds to the thickness of the intermediate layer 15.

[0048] After preparing the first part 20 and the second part 30 described above, they are joined together (joining process). An example of a joining method will be specifically described. In this embodiment, the first part 20 and the second part 30 are joined using surface-activated bonding. Surface-activated bonding is a method of joining flat bonding surfaces with exposed constituent atoms, and it can significantly lower the bonding temperature compared to other bonding methods.

[0049] Specifically, the first component 20 and the second component 30 are placed inside the chamber 40, and the chamber 40 is made into a near-vacuum environment. Under near-vacuum conditions, a surface-activated beam 42 is irradiated from a beam source 41 onto the joint surface 20a of the first component 20 and the joint surface 30a of the second component 30.

[0050] The joining surface 20a is the surface of the first part 20 that is joined to the second part 30. In the configuration shown in Figure 2, the joining surface 20a is the first surface 151a of the intermediate layer 151. The joining surface 30a is the surface of the second part 30 that is joined to the first part 20. In the configuration shown in Figure 2, the joining surface 30a is the first surface 152a of the intermediate layer 152.

[0051] Examples of surface-activated beams 42 include ion beams such as argon (Ar) or FAB (fast atomic beam). This activates the surface irradiated with the surface-activated beam 42 (in this embodiment, the bonding surface 20a and bonding surface 30a). Specifically, oxygen and other substances adsorbed on the surface are removed, and a new surface containing dangling bonds is formed. This approximate vacuum environment has a background pressure of, for example, 1 × 10⁻⁶. -6 This is a vacuum or reduced pressure atmosphere between Pa and atmospheric pressure.

[0052] As the ion beam or FAB, in addition to argon, beams using noble gases or inert gases such as neon (Ne), krypton (Kr), xenon (Xe), and helium (He) can be employed. Since noble gases do not readily undergo chemical reactions, they do not significantly alter the chemical properties of the irradiated surface. An example of the beam source 41 is a particle beam source or a plasma generator. By accelerating the ion beam particles toward the junction surfaces 20a and 30a using a particle beam source or plasma generator, a predetermined kinetic energy can be imparted to the ion beam or FAB.

[0053] After applying a surface activation treatment to the bonding surfaces 20a and 30a, the bonding surfaces 20a and 30a are placed facing each other. At room temperature, the newly exposed bonding surfaces (surface activation treated bonding surfaces 20a and 30a) of the first component 20 and the second component 30 are brought into contact in a near-vacuum environment. This generates a bonding force due to interatomic interactions. As a result, the first component 20 and the second component 30 are firmly bonded together, and the optical element 10 is obtained. This near-vacuum environment is, for example, one with a background pressure of 1.5 × 10⁻⁶. -6 The atmosphere is a vacuum or reduced pressure below Pa. A predetermined pressure (1.5 to 2.0 MPa) may be applied to the first part 20 and the second part 30 that are in contact.

[0054] The bonding surfaces 20a and 30a may be amorphous by the above surface activation treatment. In this case, the first part 20 and the second part 30 are bonded via the amorphous layer. Amorphous refers to a substance that does not have long-range order like a crystal, but does have short-range order. The amorphous state is a state in which the crystalline structure is broken down. The amorphous layer is a layer in which the crystallinity is below a certain level.

[0055] The amorphous layer contains impurities other than the materials constituting the heat sink 14 and the laser medium 11, including elements constituting the ion beam or FAB (hereinafter referred to as "beam elements"), and housing material constituting the beam housing of the ion beam or FAB. The beam elements are, for example, Ar (argon) or Ne (neon). The housing material is, for example, Fe (iron), Ni (nickel), or Cr (chromium). The amount of beam elements contained in the amorphous layer is so small that it does not affect the oscillation or amplification of the laser light L.

[0056] After joining the first component 20 and the second component 30 via an amorphous layer, the optical element 10 may be heat-treated in a heating furnace to raise its temperature to a predetermined level. This anneals the optical element 10, causing the amorphous layer of the optical element 10 to undergo epitaxial growth and crystallize.

[0057] The predetermined temperature (also referred to as the crystallization temperature or epitaxial growth temperature) is lower than the melting points of the heat sink 14 and the laser medium 11. The predetermined temperature is 100°C or higher and lower than the melting point of the material constituting the amorphous layer. In one embodiment, the predetermined temperature is approximately 865°C, which is about half of the melting point of the heat sink 14 and the laser medium 11, which is approximately 2000°C. The predetermined temperature is, for example, 1900°C or lower. The predetermined temperature is low enough not to affect the dielectric multilayer film 12, for example, 200°C or 300°C. The heating time of the optical element 10 is, for example, several hours to several tens of hours. For example, in the case of a long heating process, the predetermined temperature may be 100°C or lower.

[0058] This section describes the case where the above-mentioned surface activation treatment is applied during the bonding process. However, the surface activation treatment may be omitted. Au is the most stable material, and it can be stored for a long period of time while maintaining its surface activity by adjusting the storage conditions. Therefore, if the intermediate layer 15 is Au and can be stored for a long period of time while maintaining its surface activity, the surface activation treatment may be omitted.

[0059] In the optical element 10, the dielectric multilayer film 12 functions as a totally reflective film. The thickness t of the dielectric multilayer film 12 is greater than the seepage length d of the evanescent wave EW generated by the reflection of the laser light L incident from the laser medium 11 side. In this configuration, even if high-power laser light L is totally reflected by the dielectric multilayer film 12, the resulting evanescent wave EW is not absorbed by the first metal layer 13, the heat sink 14, etc. Therefore, the optical element 10 can be used stably even with high-power laser light L. High-power laser light L refers to laser light with an average output of 1 kW or more (for example, megawatts or more).

[0060] The first metal layer 13 contains a group 4 element (for example, Ti) or a group 6 element (for example, Cr). The coefficient of linear expansion of such a first metal layer 13 is between the coefficient of linear expansion of the dielectric (laser medium 11, dielectric multilayer film 12, etc.) and the coefficient of linear expansion of the heat sink 14. Therefore, compared to when the first metal layer 13 is not present, the coefficient of linear expansion changes stepwise from the laser medium 11 side toward the heat sink 14 inside the optical element 10. That is, the rate of change of the coefficient of linear expansion from the laser medium 11 side toward the heat sink 14 is smaller than when the first metal layer 13 is not present. Therefore, for example, even if heat is generated in the laser medium 11 due to the influence of high-power laser light L, the optical element 10 is less likely to be damaged.

[0061] The second metal layer 16 contains a tenth element (for example, Ni, Pt, etc.). The coefficient of linear expansion of such a second metal layer 16 is between the coefficient of linear expansion of the first metal layer 13 and the coefficient of linear expansion of the heat sink 14. Therefore, in the configuration with the second metal layer 16, the coefficient of linear expansion changes stepwise from the laser medium 11 side toward the heat sink 14 inside the optical element 10 compared to the configuration without the second metal layer 16. That is, the rate of change of the coefficient of linear expansion from the laser medium 11 side toward the heat sink 14 is smaller than in the configuration without the second metal layer 16. Therefore, in the configuration with the second metal layer 16, even if heat is generated in the laser medium 11 due to the influence of high-power laser light L, for example, the optical element 10 is less likely to be damaged.

[0062] In the example of the optical element manufacturing method described using Figure 2, an optical element 10 can be manufactured. That is, in the example of the optical element manufacturing method described using Figure 2, an optical element 10 that can be used stably with high-power laser light L can be manufactured.

[0063] When the optical element 10 is manufactured using surface-active bonding, as shown in Figure 2, the first component 20 including the laser medium 11 and the second component 30 including the heat sink 14 can be directly bonded (specifically, using bonding forces due to interatomic interactions), thus creating a strong bond. In this case, since no adhesive layer is used, the optical element 10 is less likely to be damaged by the heat generated in the laser medium 11.

[0064] In a configuration that includes an intermediate layer 15, where the intermediate layer 15 is formed from Au or an Au alloy, the optical element 10 can be manufactured using a first component 20 and a second component 30 having intermediate layers 151 and 152, which are to become the intermediate layer 15, on the joining side, as shown in the example of the manufacturing method described with reference to Figure 2. Since Au and the like are resistant to oxidation, the joining surfaces 20a and 30a can be kept clean. As a result, the first component 20 and the second component 30 can be joined more firmly. When the intermediate layer 15 is formed from Au, as mentioned above, surface activation treatment can sometimes be omitted. As a result, the optical element 10 can be manufactured more easily.

[0065] (Variation 1) In the manufacturing method of the optical element 10 described with reference to Figure 2, the intermediate layer 15 is divided into intermediate layer 151 and intermediate layer 152 and arranged in the first component 20 and the second component 30. However, as shown in Figure 3, the optical element 10 may also be manufactured using a second component 30A that does not have the intermediate layer 152 and a first component 20A that has the intermediate layer 15 instead of the intermediate layer 151.

[0066] The first part 20A is the same as the first part 20, except that it has an intermediate layer 15 instead of an intermediate layer 151. In the first part 20A, the first surface 15a of the intermediate layer 15 is the bonding surface 20a. The method for preparing the first part 20A is the same as the method for preparing the first part 20, except that it forms an intermediate layer 15 instead of an intermediate layer 151.

[0067] The second component 30A is the same as the second component 30, except that it does not have an intermediate layer 152. The second component 30 is a laminate of a heat sink 14 and a second metal layer 16, and the first surface 16a of the second metal layer 16 is the bonding surface 30a. The first surface 16a is the surface of the second metal layer 16 opposite to the heat sink 14. The preparation method for the second component 30A is the same as the preparation method for the second component 30, except that it does not form an intermediate layer 152.

[0068] The method for manufacturing the optical element 10 using the first component 20A and the second component 30A is the same as the method described using Figure 2, except that the first component 20A and the second component 30A are used instead of the first component 20 and the second component 30. Therefore, the manufacturing method of the modified example 1 has the same effects and advantages as the manufacturing method described using Figure 2.

[0069] The joining surface 30a of the second component 30A is the first surface 16a of the second metal layer 16. Since an oxide film is easily formed on the first surface 16a of the second metal layer 16, in Modification 1, before joining the first component 20A and the second component 30A, surface activation treatment of the joining surface 30a is performed using a surface-activated beam 42, as described using Figure 2. The conditions for surface activation treatment are the same as described using Figure 2. In order to perform surface activation treatment on the second component 30A, surface activation treatment is usually also performed on the first component 20A. However, the first component 20A has an intermediate layer 15. Therefore, as with the first component 20, if the intermediate layer 15 is formed from Au, the material is stable, and the storage conditions are good, surface activation treatment may be omitted.

[0070] (Second Embodiment) Figure 4 is a schematic diagram showing the general configuration of the optical element 10A according to the second embodiment. Optical element 10 differs from optical element 10 in that it does not have an intermediate layer 15. In optical element 10A, the first metal layer 13 and the second metal layer 16 are in contact. The configuration of optical element 10A is the same as that of optical element 10, except for the above difference. Therefore, optical element 10A has the same effects as optical element 10. Although not shown in Figure 4, optical element 10A may also have a dielectric multilayer film 17 that functions as an anti-reflective coating.

[0071] An example of a manufacturing method for the optical element 10A is described below. The manufacturing method for the optical element 10A is the same as that for the optical element 10, except that the first component 20B and the second component 30A shown in Figure 5 are prepared and joined together to manufacture the optical element 10A. Therefore, the manufacturing method for the optical element 10A has the same effects and advantages as the manufacturing method for the optical element 10.

[0072] The first component 20B differs from the first component 20 in that it does not have an intermediate layer 151. Aside from this difference, the configuration of the first component 20B is the same as that of the first component 20. The bonding surface 20a of the first component 20B is the first surface 13a of the first metal layer 13. The preparation method for the first component 20B is the same as that for the first component 20, except that the intermediate layer 151 is not formed.

[0073] The second part 30A is the same as the second part 30A described in the above modified example 1, so its description is omitted. The bonding surface 30a of the second part 30A is the first surface 16a of the second metal layer 16.

[0074] The bonding surface 20a of the first component 20B is the first surface 13a of the first metal layer 13, and the bonding surface 30a of the second component 30A is the first surface 16a of the second metal layer 16. Oxide films are easily formed on the first surfaces 13a and 16a. Therefore, when bonding the first component 20B and the second component 30A using surface-activated bonding, a surface-activated beam 42 is used to perform surface-activated bonding on the bonding surfaces 20a and 30a, as described using Figure 2. The conditions for the surface-activated bonding are the same as described using Figure 2.

[0075] (Modification 2) In the manufacturing method of the optical element 10A described using Figure 5, the second component 30A had a second metal layer 16. However, as shown in Figure 6, the optical element 10A may also be manufactured using a first component 20C having a second metal layer 16 and a second component 30B not having a second metal layer 16.

[0076] The first part 20C is the same as the first part 20B, except that a second metal layer 16 is formed on the first metal layer 13. The joining surface 20a of the first part 20C is the second surface 16b of the second metal layer 16. The second surface 16b is the surface of the second metal layer 16 opposite to the first surface 16a. The preparation method for the first part 20C is the same as the preparation method for the first part 20B, except that the second metal layer 16 is further formed on the first metal layer 13.

[0077] The second component 30B is the same as the second component 30A except that it does not have the second metal layer 16. Therefore, in the modified example 2, the second component 30B is the heat sink 14, and the bonding surface 30a of the second component 30B is the first surface 14a of the heat sink 14.

[0078] The method for manufacturing the optical element 10A using the first component 20C and the second component 30B is the same as described with reference to Figure 5, except that the first component 20C and the second component 30B are used instead of the first component 20B and the second component 30A. The second surface 16b of the second metal layer 16, which is the bonding surface 20a, and the first surface 14a of the heat sink 14, which is the bonding surface 30a, are prone to oxide film formation. Therefore, in the modified example 2 as well, when the first component 20C and the second component 30B are surface-activated bonding, a surface-activated treatment is performed on the bonding surface 20a and the bonding surface 30a using a surface-activated beam 42, as described with reference to Figure 2. The conditions for the surface-activated treatment are the same as described with reference to Figure 2.

[0079] Except for using the first component 20C and the second component 30B instead of the first component 20B and the second component 30A, the manufacturing method of Modified Example 2 is the same as the manufacturing method of the optical element 10A described with reference to Figure 5. Therefore, the manufacturing method of Modified Example 2 has the same effects and advantages as the manufacturing method of the optical element 10A described with reference to Figure 5.

[0080] (Third embodiment) Figure 7 is a schematic diagram showing the general configuration of the optical element 10B according to the third embodiment. The optical element 10B differs from the optical element 10 in that it does not have an intermediate layer 15 and a second metal layer 16. In the optical element 10B, a heat sink 14 is arranged on the first metal layer 13. The configuration of the optical element 10B other than the above difference is the same as that of the optical element 10. Therefore, the optical element 10B has the same effects and advantages as the optical element 10.

[0081] An example of a manufacturing method for the optical element 10B is described below. The manufacturing method for the optical element 10B is the same as that for the optical element 10, except that the first component 20B and the second component 30B shown in Figure 8 are prepared and joined together to manufacture the optical element 10B. Therefore, the manufacturing method for the optical element 10B has the same effects and advantages as the manufacturing method for the optical element 10.

[0082] The first part 20B is the same as the first part 20B shown in Figure 5, so its description is omitted. The second part 30B is the same as the second part 30B shown in Figure 6, so its description is omitted.

[0083] The bonding surface 20a of the first component 20B is the first surface 13a of the first metal layer 13, as explained with reference to Figure 5. The bonding surface 30a of the second component 30B is the first surface 14a of the heat sink 14, as explained with reference to Figure 6. Oxide films are easily formed on the first surfaces 13a and 14a. When surface-activated bonding is performed on the first component 20B and the second component 30B during the manufacturing of the optical element 10B, a surface-activated treatment is performed on the bonding surfaces 20a and 30a using a surface-activated beam 42, as explained with reference to Figure 2. The conditions for the surface-activated treatment are the same as explained with reference to Figure 2.

[0084] Next, various forms of laser devices utilizing optical elements will be described. The following description will focus on a form using optical element 10, but optical elements 10A and 10B may be used instead. Laser devices utilizing optical element 10 (or optical element 10A or optical element 10B) are applicable to measurement, analysis, display, processing, and medical applications (including diagnosis and treatment), and may be incorporated into devices in the exemplified fields.

[0085] (Fourth Embodiment) Figure 9 is a schematic diagram of an example of a laser device using optical elements. The laser device 100 shown in Figure 9 is a laser oscillator. As shown in Figure 9, the laser device 100 has an optical element 10 and an output mirror 111.

[0086] In the laser device 100, the dielectric multilayer film 12 of the optical element 10 functions as a total reflection mirror with respect to the laser light L. In the laser device 100, the dielectric multilayer film 12 and the output mirror 111 constitute the optical resonator 101. The optical element 10 is arranged so that the laser medium 11 is located within the optical resonator 101. The output mirror 111 only needs to have the reflection and transmission characteristics necessary to function as an output mirror 111 in the optical resonator 101. The output mirror 111 may be a partial reflection mirror.

[0087] When the laser device 100 outputs laser light L, the laser medium 11 is irradiated with excitation light 102. This generates stimulated emission light within the laser medium 11, and the stimulated emission light propagates through the optical resonator 101. As a result, laser oscillation occurs, and laser light L is output from the output mirror 111.

[0088] The laser device 100 may have a light source unit 103 that outputs excitation light 102. The laser device 100 may have a Q-switch element 104 between the optical element 10 and the output mirror 111 within the optical resonator 101. The Q-switch element 104 may be a known Q-switch element. The laser device 100 may have a mode-lock element or a wavelength conversion element instead of the Q-switch element 104. The mode-lock element and wavelength conversion element may also be a known mode-lock element and wavelength conversion element. If the laser device 100 includes a wavelength conversion element located on the output side of the laser device 100 relative to the optical element 10, the output mirror 111 may have a wavelength separation function.

[0089] The laser device 100 includes an optical element 10. As described in the first embodiment, the optical element 10 is resistant to damage from high-power laser light L, and as a result, the laser device 100 can be used stably. Therefore, the laser device 100 can also stably output high-power laser light L.

[0090] Since the laser device 100 is equipped with an optical element 10 that can be used stably with high-power laser light L, it is easy to stably output high-power short-pulse laser light using the Q-switch element 104. Therefore, the optical element 10 can be more effectively applied to laser devices that have the Q-switch element 104.

[0091] (Variation 3) Figure 10 is a schematic diagram showing another example of a laser device, which is a laser oscillator. Laser device 100A differs from laser device 100 mainly in that it further includes a first total reflection mirror 112A, and the dielectric multilayer film 12 of the optical element 10, the output mirror 111, and the first total reflection mirror 112A constitute an optical resonator 101A. Since laser device 100A also includes an optical element 10, it has the same effects as laser device 100.

[0092] The laser device 100A may also include a Q-switching element 104, similar to the case of the laser device 100. The laser device 100A may also include a mode-locking element or a wavelength conversion element instead of the Q-switching element 104. If the laser device 100A includes a wavelength conversion element, the output mirror 111 may have a wavelength separation function, similar to the case of the laser device 100.

[0093] In the laser device 100A, the optical resonator 101 is composed of a dielectric multilayer film 12, an output mirror 111, and a first total reflection mirror 112A. Therefore, the optical path of the laser beam L from the first total reflection mirror 112A to the output mirror 111 is bent at the position of the dielectric multilayer film 12.

[0094] The laser device 100A may also include a light source unit 103 that outputs excitation light 102.

[0095] (Modification 4) Figure 11 is a schematic diagram showing another example of a laser device, which is a laser oscillator. Laser device 100B differs from laser device 100A mainly in that it has multiple optical elements 10 between the first total reflection mirror 112A and the output mirror 111. Laser device 100B is a multi-stage medium type laser oscillator.

[0096] Since the laser device 100B also includes optical elements 10, the laser device 100B has the same effects as the laser device 100 and the laser device 100A. The laser device 100B has multiple optical elements 10, and the laser light L is amplified by each optical element 10. Therefore, the laser device 100B can output a higher power laser light L. In this way, even when the output of the laser light L is higher, the laser device 100B is less prone to damage due to the use of optical elements 10, and as a result, it is easier to use stably. Therefore, optical elements 10 can be more effectively applied to multi-stage medium type laser oscillators such as the laser device 100B.

[0097] The laser device 100B may also include a Q-switching element 104, as in the cases of laser devices 100 and 100A. The laser device 100B may also include a mode-locking element or a wavelength conversion element instead of the Q-switching element 104. If the laser device 100B includes a wavelength conversion element, the output mirror 111 may have a wavelength separation function, as in the cases of laser devices 100 and 100A.

[0098] In the laser device 100B, the optical resonator 101B is composed of dielectric multilayer films 12, each of the multiple optical elements 10, the output mirror 111, and the first total reflection mirror 112A. Therefore, the optical path of the laser beam L from the total reflection mirror to the output mirror 111 bends at the position of each dielectric multilayer film 12.

[0099] The laser device 100B may also include a light source unit 103 that outputs excitation light 102.

[0100] (Variation 5) Figure 12 is a schematic diagram showing another example of a laser device, which is a laser oscillator. Laser device 100C is another example of a multi-stage medium type laser oscillator.

[0101] The laser device 100C includes a first total reflection mirror 112A, an output mirror 111, and a set of multiple elements 120. The first total reflection mirror 112A and the output mirror 111 are arranged along a first direction X.

[0102] Each of the multiple element sets 120 comprises a first optical element 121A, a second optical element 121B, a polarizing beam splitter 122, a first waveplate 123A, and a second waveplate 123B.

[0103] The first optical element 121A and the second optical element 121B are the same elements as the optical element 10. The first optical element 121A and the second optical element 121B are spaced apart in a direction that crosses the first direction X (in Figure 12, a direction perpendicular to the first direction X), and are arranged so that the laser medium 11 of the first optical element 121A and the second optical element 121B face each other.

[0104] The polarizing beam splitter 122 is positioned between the first optical element 121A and the second optical element 121B.

[0105] The first waveplate 123A is positioned between the first optical element 121A and the polarizing beam splitter 122. The first waveplate 123A is an element that changes the polarization state of the laser beam L when the laser beam L is directed from the polarizing beam splitter 122 to the first optical element 121A and when the laser beam L is directed from the first optical element 121A to the polarizing beam splitter 122, so that the optical path of the laser beam L is changed by the polarizing beam splitter 122. An example of the first waveplate 123A is a λ / 4 plate.

[0106] The second waveplate 123B is positioned between the second optical element 121B and the polarizing beam splitter 122. The second waveplate 123B is an element that changes the polarization state of the laser beam L when the laser beam L is directed from the polarizing beam splitter 122 to the second optical element 121B and when the laser beam L is directed from the second optical element 121B to the polarizing beam splitter 122, so that the optical path of the laser beam L is changed by the polarizing beam splitter 122. An example of the second waveplate 123B is a λ / 4 plate.

[0107] The set of multiple elements 120 is arranged such that the first total reflection mirror 112A, multiple polarizing beam splitters 122, and output mirror 111 are aligned along the first direction X.

[0108] In the laser device 100C, the optical resonator 101C is formed by the dielectric multilayer film 12 of the first optical element 121A and the second optical element 121B, the first total reflection mirror 112A, and the output mirror 111. Multiple polarizing beam splitters 122, multiple first waveplates 123A, and multiple second waveplates also affect the optical path of the laser beam L, and therefore can also be part of the optical resonator 101.

[0109] In the laser device 100C, the first optical element 121A and the second optical element 121B are optical elements 10. Therefore, the laser device 100C has the same effects and advantages as the laser device 100. Since the laser device 100C has the first optical element 121A and the second optical element 121B, it has multiple optical elements 10. The effects and advantages associated with the laser device 100C having multiple optical elements 10 are the same as those in the case of the laser device 100B.

[0110] The laser device 100C may also include a Q-switching element 104, similar to the cases of laser devices 100, 100A, and 100B. The Q-switching element 104 may be positioned, for example, between the polarizing beam splitter 122, which is located upstream of the output mirror 111 (closest to the output mirror 111), and the output mirror 111. The laser device 100C may also include a mode-locking element or a wavelength-converting element instead of the Q-switching element 104. If the laser device 100C includes a wavelength-converting element, the output mirror 111 may have a wavelength-separating function, similar to the cases of the laser device 100, etc.

[0111] The laser device 100C may also include a light source unit 103 that outputs excitation light 102.

[0112] (Fifth embodiment) Figure 13 is a schematic diagram showing another example of a laser device using optical elements. The laser device 100D shown in Figure 13 is a laser amplifier. The laser device 100D includes an optical element 10, a first polarizing beam splitter 105A, and a Faraday element 106.

[0113] The optical element 10 is arranged such that the laser medium 11 faces the first polarizing beam splitter 105A.

[0114] The Faraday element 106 is positioned between the optical element 10 and the first polarizing beam splitter 105A. An example of the Faraday element 106 is a Faraday rotor. The Faraday element 106 controls the polarization state of the laser beam L so that the amplified laser beam L is reflected by the first polarizing beam splitter 105A and output from the laser device 100D.

[0115] When amplifying the laser beam L with the laser device 100D, the optical element 10 is irradiated with excitation light 102 to excite the laser medium 11. In this state, the input laser beam L is incident on the first polarizing beam splitter 105A from the opposite side of the optical element 10. The laser beam L passes through the first polarizing beam splitter 105A and the Faraday element 106 and is incident on the optical element 10. The incident laser beam L causes stimulated emission in the laser medium 11, and the laser beam L is amplified. The amplified laser beam L is totally reflected by the dielectric multilayer film 12, passes through the Faraday element 106 and is incident on the first polarizing beam splitter 105A. The polarization state of the laser beam L is changed as it passes through the Faraday element 106 from the optical element 10 to the first polarizing beam splitter 105A. As a result, the amplified laser beam L is reflected by the first polarizing beam splitter 105A and output from the laser device 100D.

[0116] The laser device 100D may also include a light source unit 103, similar to the case of the laser device 100.

[0117] The laser device 100D is equipped with an optical element 10. Therefore, the laser device 100D is less likely to be damaged even when generating high-power laser light L by amplifying the input laser light L. Thus, the laser device 100D can be used stably. Accordingly, the optical element 10 can be effectively applied to the laser device 100D.

[0118] (Experimental variation 6) Figure 14 is a schematic diagram showing another example of a laser device as a laser amplifier. Laser device 100E differs from laser device 100D mainly in that it has a first total reflection mirror 112A.

[0119] The first total reflection mirror 112A is positioned on the same side as the first polarizing beam splitter 105A with respect to the optical element 10 (more specifically, with respect to the laser medium 11). The first total reflection mirror 112A is positioned with respect to the optical element 10 such that the optical path of the laser beam L between the first polarizing beam splitter 105A and the optical element 10 is different from the optical path of the laser beam L between the optical element 10 and the first total reflection mirror 112A.

[0120] The Faraday element 106 is positioned between the optical element 10 and the first total reflection mirror 112A. The Faraday element 106 may also be positioned between the optical element 10 and the first polarizing beam splitter 105A.

[0121] Laser device 100E has the same configuration as laser device 100D, except that the optical path of the laser beam L differs from that of laser device 100D due to the presence of the first total reflection mirror 112A. Therefore, laser device 100E has the same effects and advantages as laser device 100D.

[0122] The laser device 100E may also include a light source unit 103, similar to the case of the laser device 100.

[0123] (Sixth Embodiment) Figure 15 is a schematic diagram of another example of a laser device using optical elements. The laser device 100F shown in Figure 15 is a laser regenerative amplifier. The laser device 100F includes an optical element 10, a first total reflection mirror 112A, a first polarizing beam splitter 105A, an electro-optic element 107, a second polarizing beam splitter 105B, and a Faraday element 106.

[0124] The optical element 10 is positioned such that the laser medium 11 faces the first total reflection mirror 112A. The second polarizing beam splitter 105B and the electro-optic element 107 are positioned between the first total reflection mirror 112A and the optical element 10. The second polarizing beam splitter 105B and the electro-optic element 107 are positioned in this order from the first total reflection mirror 112A toward the optical element 10. That is, the optical element 10, the electro-optic element 107, the second polarizing beam splitter 105B, and the first total reflection mirror 112A are positioned in this order along one direction.

[0125] The first polarizing beam splitter 105A and the Faraday element 106 are arranged in the order of Faraday element 106 and first polarizing beam splitter 105A relative to the second polarizing beam splitter 105B. That is, the second polarizing beam splitter 105B, the Faraday element 106 and the first polarizing beam splitter 105A are arranged in this order along one direction.

[0126] The direction in which the optical element 10, the electro-optic element 107, the second polarizing beam splitter 105B, and the first total reflection mirror 112A are arranged is different from the direction in which the second polarizing beam splitter 105B, the Faraday element 106, and the first polarizing beam splitter 105A are arranged.

[0127] In the configuration of the laser device 100F, the first total reflection mirror 112A and the dielectric multilayer film 12 of the optical element 10 constitute the optical resonator 101D. The laser light L is amplified as it repeatedly propagates within the optical resonator 101D.

[0128] The electro-optic element 107 functions as an optical switch to extract the laser light L propagating within the optical resonator 101D to the Faraday element 106 and the first polarizing beam splitter 105A via the second polarizing beam splitter 105B. An example of the electro-optic element 107 is a Pockels cell.

[0129] In the laser device 100F, the laser beam L is amplified as it passes back and forth multiple times within the optical resonator 101D. The amplified laser beam L is then output to the outside of the laser device 100F via the second polarizing beam splitter 105B, the Faraday element 106, and the first polarizing beam splitter 105A by controlling the electro-optic element 107.

[0130] In the laser device 100F, the laser beam L is amplified as it reciprocates multiple times within the optical resonator 101D, enabling the output of an even higher-power laser beam L. Even in such cases, the optical element 10 is less susceptible to damage from the high-power laser beam L, allowing the laser device 100F to stably output a high-power laser beam L. Therefore, the optical element 10 can be more effectively applied to the laser device 100F.

[0131] As shown in Figure 15, the laser device 100F may also include a waveplate 123 between the electro-optic element 107 and the optical element 10, which contributes to the extraction of laser light L from the optical resonator 101D together with the electro-optic element 107. An example of the waveplate 123 is a λ / 4 plate.

[0132] The laser device 100F may also include a light source unit 103 that outputs excitation light 102, similar to the case of the laser device 100.

[0133] (Example 7) Figure 16 is a schematic diagram showing another example of a laser device as a laser regenerative amplifier. Laser device 100G differs from laser device 100F mainly in that it further has a second total reflection mirror 112B.

[0134] The second total reflection mirror 112B is positioned on the same side as the second polarizing beam splitter 105B with respect to the optical element 10 (more specifically, with respect to the laser medium 11). The second total reflection mirror 112B is positioned with respect to the optical element 10 such that the optical path of the laser beam L between the second polarizing beam splitter 105B and the optical element 10 is different from the optical path of the laser beam L between the optical element 10 and the second total reflection mirror 112B.

[0135] In the laser device 100G, an optical resonator 101E is formed by the first total reflection mirror 112A, the dielectric multilayer film 12 of the optical element 10, and the second total reflection mirror 112B.

[0136] The electro-optic element 107 is positioned between the second polarizing beam splitter 105B and the second total reflection mirror 112B. In the example shown in Figure 16, the electro-optic element 107 is positioned between the optical element 10 and the second total reflection mirror 112B. The electro-optic element 107 functions as an optical switch to extract the laser light L propagating within the optical resonator 101E to the Faraday element 106 and the first polarizing beam splitter 105A via the second polarizing beam splitter 105B.

[0137] Laser device 100G has the same configuration as laser device 100F, except that the optical path of the laser beam L differs from that of laser device 100F due to the presence of the second total reflection mirror 112B. Therefore, laser device 100G has the same effects and advantages as laser device 100F.

[0138] The laser device 100G may include a light source unit 103 that outputs excitation light 102, similar to the case of the laser device 100. The laser device 100G may also include a waveplate 123 that contributes to the extraction of laser light L from the optical resonator 101E, similar to the case of the laser device 100F shown in Figure 15. An example of the waveplate 123 is a λ / 4 plate. The waveplate 123 is placed between the electro-optic element 107 and the second total reflection mirror 112B.

[0139] (Variation 8) Figure 17 is a schematic diagram showing another example of a laser device that is a laser regenerative amplifier. The laser device 100H shown in Figure 17 differs from the laser device 100G mainly in that it has multiple optical elements 10 between the first total reflection mirror 112A and the second total reflection mirror 112B. The laser device 100H is a multi-stage laser regenerative amplifier.

[0140] In the laser device 100H, since multiple optical elements 10 are arranged in the optical path between the first total reflection mirror 112A and the second total reflection mirror 112B, the optical path between the first total reflection mirror 112A and the second total reflection mirror 112B bends multiple times.

[0141] In the laser device 100H, the first total reflection mirror 112A, the dielectric multilayer film 12 having multiple optical elements 10, and the second total reflection mirror 112B constitute the optical resonator 101F.

[0142] The electro-optic element 107 is positioned in the optical path between the second polarizing beam splitter 105B and the second total reflection mirror 112B. In the configuration shown in Figure 17, the electro-optic element 107 is positioned between the second total reflection mirror 112B and the optical element 10 closest to the second total reflection mirror 112B in the optical path of the laser beam L. The electro-optic element 107 functions as an optical switch to extract the laser beam L propagating within the optical resonator 101F to the Faraday element 106 and the first polarizing beam splitter 105A via the second polarizing beam splitter 105B.

[0143] Since the laser device 100H also includes optical elements 10, it has the same effects and advantages as the laser device 100G. Because the laser device 100H includes multiple optical elements 10, it can further amplify the laser light L. Even in such cases, since the optical elements 10 are less likely to be damaged by the high-power laser light L, the laser device 100H can stably output high-power laser light L. Therefore, the optical elements 10 can be applied more effectively to the laser device 100H.

[0144] The laser device 100H may also include a light source unit 103 that outputs excitation light 102, similar to the case of the laser device 100. The laser device 100H may also include a waveplate 123 that contributes to the extraction of laser light L from the optical resonator 101F, similar to the case of the laser device 100F shown in Figure 15. An example of the waveplate 123 is a λ / 4 plate. The waveplate 123 is placed between the electro-optic element 107 and the second total reflection mirror 112B.

[0145] (Extreme variation 9) Figure 18 is a schematic diagram showing another example of a laser device that is a laser regenerative amplifier. Laser device 100I differs from laser device 100G in that it has multiple element sets 120 between the first total reflection mirror 112A and the second total reflection mirror 112B. In the description of Modification 9, the first direction X and second direction Y set in Modification 5 are also used.

[0146] In the laser device 100I, the first total reflection mirror 112A, the second polarizing beam splitter 105B, the multiple element sets 120, and the second total reflection mirror 112B are arranged along the first direction X.

[0147] The configuration of the multiple element sets 120 is the same as the configuration of the element set 120 described with reference to Figure 12. That is, the element set 120 comprises a first optical element 121A, a second optical element 121B, a polarizing beam splitter 122, a first waveplate 123A, and a second waveplate 123B.

[0148] The first optical element 121A and the second optical element 121B are the same elements as the optical element 10. The first optical element 121A and the second optical element 121B are spaced apart in a direction that crosses the first direction X (in Figure 18, a direction perpendicular to the first direction X), and are arranged so that the laser medium 11 of the first optical element 121A and the second optical element 121B face each other.

[0149] The polarizing beam splitter 122 is positioned between the first optical element 121A and the second optical element 121B.

[0150] The first waveplate 123A is positioned between the first optical element 121A and the polarizing beam splitter 122. The first waveplate 123A is an element that changes the polarization state of the laser beam L when the laser beam L is directed from the polarizing beam splitter 122 to the first optical element 121A and when the laser beam L is directed from the first optical element 121A to the polarizing beam splitter 122, so that the optical path of the laser beam L is changed by the polarizing beam splitter 122. An example of the first waveplate 123A is a λ / 4 plate.

[0151] The second waveplate 123B is positioned between the second optical element 121B and the polarizing beam splitter 122. The second waveplate 123B is an element that changes the polarization state of the laser beam L when the laser beam L is directed from the polarizing beam splitter 122 to the second optical element 121B and when the laser beam L is directed from the second optical element 121B to the polarizing beam splitter 122, so that the optical path of the laser beam L is changed by the polarizing beam splitter 122. An example of the second waveplate 123B is a λ / 4 plate.

[0152] The set of multiple elements 120 is arranged such that the first total reflection mirror 112A, multiple polarizing beam splitters 122, and the second total reflection mirror 112B are aligned along the first direction X.

[0153] In the laser device 100I, the optical resonator 101G is formed by the first total reflection mirror 112A, the dielectric multilayer film 12 on the first optical element 121A and the second optical element 121B, and the second total reflection mirror 112B. Multiple polarizing beam splitters 122, multiple first waveplates 123A, and multiple second waveplates 123B also affect the optical path of the laser beam L, and therefore may also be part of the optical resonator 101G.

[0154] The electro-optic element 107 is positioned between the second polarizing beam splitter 105B and the second total reflection mirror 112B in the first direction X. In the example shown in Figure 18, the electro-optic element 107 is positioned between the second polarizing beam splitter 105B and the element set 120 closest to the second polarizing beam splitter 105B among the multiple element sets 120. The electro-optic element 107 functions as an optical switch to extract the laser light L propagating within the optical resonator 101G to the Faraday element 106 and the first polarizing beam splitter 105A via the second polarizing beam splitter 105B.

[0155] The laser device 100I includes a first optical element 121A and a second optical element 121B, which are optical elements 10. In other words, the laser device 101I includes multiple optical elements 10. Therefore, the laser device 100I has the same effects and functions as the laser device 100H.

[0156] The laser device 100I may also include a light source unit 103 that outputs excitation light 102, similar to the case of the laser device 100. The laser device 100I may also include a waveplate 123 that contributes to the extraction of laser light L from the optical resonator 101G, similar to the case of the laser device 100F shown in Figure 15. An example of the waveplate 123 is a λ / 4 plate. The waveplate 123 is located outside the element set 120, between the electro-optic element 107 and the second total reflection mirror 112B. In Figure 18, the waveplate 123 is located between the polarizing beam splitter 122 of the element set 120 closest to the second total reflection mirror 112B and the second total reflection mirror 112B.

[0157] The present invention is not limited to the various embodiments described herein, but includes the scope set forth in the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0158] The optical element may have a parasitic oscillation prevention section 18 on the second surface 11b of the laser medium 11, as shown in Figure 19, for optical element 10C. Optical element 10C corresponds to an element comprising optical element 10 and a parasitic oscillation prevention section 18 provided on optical element 10. Optical element 10C may also include optical element 10A or optical element 10B instead of optical element 10. The parasitic oscillation prevention section 18 is transparent to the laser light L and excitation light 102. Examples of materials for the parasitic oscillation prevention section 18 include undoped laser material (e.g., YAG), sapphire (Al2O3), etc. In one embodiment, the material of the laser medium 11 is Yb-doped YAG (Yb:YAG), and the material of the parasitic oscillation prevention section 18 is YAG or Al2O3. By providing the parasitic oscillation prevention section 18, the generated parasitic oscillation light passes through the region of the parasitic oscillation prevention section 18, which has no gain, thereby suppressing amplification and preventing parasitic oscillation. A dielectric multilayer film 17 for parasitic oscillation prevention (see Figure 1) may be formed on the surface of the parasitic oscillation prevention section 18 (the surface opposite to the laser medium 11).

[0159] The optical element may have an absorption section 19 on the side surface of the laser medium 11 for preventing parasitic oscillation, as shown in the optical element 10D in Figure 20. In this case, a dielectric multilayer film 12 or the like is arranged on the layer formed by the laser medium 11 and the absorption section 19. An example of the material for the absorption section 19 is, for example, Cr or Sm-doped YAG (Cr:YAG or Sm:YAG) or a garnet-based material with added Cr or Sm for laser oscillation at a wavelength of 1 μm. In one embodiment, the material of the laser medium 11 is Yb:YAG, and the material of the absorption section 19 is Cr:YAG. The material for the absorption section 19 may also be Nd:YAG, or other materials with added Yb or Nd. Examples of materials for the absorption section 19 include vanadium-doped YAG (V:YAG) for a wavelength of 1.3 μm, and Co spinel for a wavelength of 1.5 μm. In the configuration equipped with an absorption unit 19, the generated parasitic oscillation light is absorbed by the absorption unit 19 (for example, Cr:YAG). Since the parasitic oscillation light can be eliminated by the absorption unit 19 in this way, parasitic oscillation can be prevented. A dielectric multilayer film as an anti-reflective film may be formed on the surface of the layer composed of the laser medium 11 and the absorption unit 19 that is opposite to the dielectric multilayer film 12.

[0160] In the explanation so far, the first intermediate layer of the optical element has been described as a dielectric multilayer film 12. However, the first intermediate layer may be the intermediate layer 50 shown in Figure 21. Figure 21 is a schematic diagram of an optical element 10E that includes an intermediate layer 50. The optical element 10E differs from the optical element 10 in that it has an intermediate layer (first intermediate layer) 50 instead of a dielectric multilayer film 12, but its other configurations are the same as those of the optical element 10.

[0161] The intermediate layer 50 comprises a dielectric multilayer film 51 formed on the laser medium 11 and a nonmetallic heat transfer layer 52 formed on the dielectric multilayer film 51.

[0162] The dielectric multilayer film 51 totally reflects the laser light L generated or amplified by stimulated emission from the laser medium 11. In one embodiment, the dielectric multilayer film 51 functions as an HR coating layer for the laser light L. The material of the dielectric multilayer film 51 may be the same as that of the dielectric multilayer film 12.

[0163] Examples of materials for the nonmetallic heat transfer layer 52 are nonmetallic materials having high thermal conductivity. The nonmetallic heat transfer layer 52 may be formed from, for example, diamond, silicon carbide (SiC), or nitrides. An example of a nitride is aluminum nitride (AlN). The nonmetallic heat transfer layer 52 can function as a heat spreader.

[0164] The intermediate layer 50 has a thickness such that the evanescent wave EW (see Figure 1) generated when laser light generated or amplified by the laser medium 11 is totally reflected by the dielectric multilayer film 51 does not reach the first metal layer 13. In other words, the thickness of the intermediate layer 50 is longer than the seepage length of the evanescent wave EW and can be the same as the thickness of the dielectric multilayer film 12 shown in Figure 1. Since the intermediate layer 50 having the above thickness has a dielectric multilayer film 51 and a non-metallic heat transfer layer 52, the thickness of the dielectric multilayer film 51 may be thinner than the thickness of the dielectric multilayer film 12. The non-metallic heat transfer layer 52 may be a layer for adjusting the thickness of the intermediate layer 50. The thickness of the intermediate layer 50 may be thicker than the dielectric multilayer film 12.

[0165] The optical element 10E can be manufactured in the same manner as the optical element 10, except that a first component having an intermediate layer 50 is used instead of the dielectric multilayer film 12 in the first component 20. The first component having the intermediate layer 50 can be prepared, for example, by performing the steps of forming a dielectric multilayer film 51 on a laser medium 11 and forming a nonmetallic heat transfer layer 52 on the dielectric multilayer film 51. The nonmetallic heat transfer layer 52 may be provided on the dielectric multilayer film 51 by bonding a heat transfer body formed from an example such as diamond to the dielectric multilayer film 51.

[0166] The intermediate layer 50, like the dielectric multilayer film 12, has a thickness such that the evanescent wave EW (see Figure 1) described above does not reach the first metal layer 13. Therefore, the intermediate layer 50 and the optical element 10E having it have the same effects as the optical element 10. The non-metallic heat transfer layer 52 of the intermediate layer 50 can function as a heat spreader. Therefore, the heat generated in the laser medium 11 is easily dissipated as it is diffused in the in-plane direction, and localized temperature rises are less likely to occur, making the optical element 10E less susceptible to damage.

[0167] In optical elements 10A, 10B, 10C, and 10D, an intermediate layer 50 may be used instead of the dielectric multilayer film 12.

[0168] In the laser apparatus described using Figures 13, 14, 15, 16, 17, and 18, a Faraday element 106 was used as an optical path control element for extracting the laser light L. However, other known elements that are used in laser amplifiers (including laser regenerative amplifiers) and can achieve a similar function may be used. For example, a wavelength plate (e.g., a λ / 4 plate) may be used instead of the Faraday element.

[0169] In the laser device (laser regenerative amplifier) ​​described using Figures 15, 16, 17, and 18, an electro-optic element was used as the optical switching element (or optical path control element) for extracting laser light from the optical resonator. However, other known elements used in laser regenerative amplifiers that can achieve similar functions may also be used.

[0170] The number of stages in the multi-stage medium-type laser oscillator in the above modifications 4 and 5 is not limited to the number of stages shown in Figures 11 and 12. Two or more stages are sufficient for a multi-stage medium-type laser oscillator. Similarly, the number of stages in the multi-stage laser regenerative amplifier in the above modifications 8 and 9 is not limited to the number of stages shown in Figures 17 and 18. Two or more stages are sufficient for a multi-stage laser regenerative amplifier.

[0171] The various embodiments and modifications described above may be combined as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0172] 10, 10A, 10B, 10C, 10D, 10E…Optical elements, 11…Laser medium, 11a…First surface, 11b…Second surface, 12…Dielectric multilayer film (first intermediate layer), 12a…First surface, 13…First metal layer, 13a…First surface, 14…Heat sink, 14a…First surface, 15…Intermediate layer (second intermediate layer), 15a…First surface, 16…Second metal layer, 16a…First surface, 16b…Second surface, 17…Dielectric Body multilayer film, 18... Parasitic oscillation prevention section, 19... Absorption section, 20, 20A, 20B, 20C... First component, 20a... Junction surface, 30, 30A, 30B... Second component, 30a... Junction surface, 40... Chamber, 41... Beam source, 42... Surface-activated beam, 50... Intermediate layer (first intermediate layer), 51... Dielectric multilayer film, 52... Non-metallic heat transfer layer, 100, 100A, 100B, 100C, 100D, 100 E, 100F, 100G, 100H, 100I…Laser device, 101, 101A, 101B, 101C, 101D, 101E, 101F, 101G…Optical resonator, 102…Excitation light, 103…Light source, 104…Q-switch element, 105A…First polarizing beam splitter, 105B…Second polarizing beam splitter, 106…Faraday element, 107…Electro-optic element, 111…Output Mirror, 112A...First total reflection mirror, 112B...Second total reflection mirror, 120...Element set, X...First direction, 121A...First optical element, 121B...Second optical element, 122...Polarizing beam splitter, 123...Waveplate, 123A...First waveplate, 123B...Second waveplate, 151...Intermediate layer, 151a...First surface, 152...Intermediate layer, 152a...First surface, L...Laser light, EW...Evanescent wave.

Claims

1. Laser medium and A first intermediate layer provided on the laser medium, A first metal layer formed in the first intermediate layer and containing a group 4 or group 6 element, A heat sink containing metal is provided on the first metal layer, Equipped with, The first intermediate layer includes a dielectric multilayer film formed on the laser medium that totally reflects the laser light generated or amplified by the laser medium. The first intermediate layer is thicker than the seepage length of the evanescent wave generated by the reflection of light incident from the laser medium side by the dielectric multilayer film. Optical element.

2. The first metal layer and the heat sink are disposed between them and further comprise a second metal layer containing a Group 10 element. The optical element according to claim 1.

3. The material of the second metal layer is nickel or platinum. The optical element according to claim 2.

4. The material further comprises a second intermediate layer disposed between the first metal layer and the second metal layer, The material of the second intermediate layer is gold or a gold alloy. The optical element according to claim 2 or 3.

5. The material of the first metal layer is chromium or titanium. The optical element according to any one of claims 1 to 3.

6. The material of the heat sink is copper, copper tungsten, copper molybdenum, iron, aluminum, or aluminum-silicon carbide composite. The optical element according to any one of claims 1 to 3.

7. The first metropolitan layer is, The dielectric multilayer film, A nonmetallic heat transfer layer disposed between the dielectric multilayer film and the first metal layer, Having, The optical element according to any one of claims 1 to 3.

8. The material of the non-metallic heat transfer layer is diamond, silicon carbide, or nitride. The optical element according to claim 7.

9. The optical element is as described in any one of claims 1 to 3. Laser device.

10. Preparation steps include preparing a first component containing a laser medium and a second component containing a heat sink containing metal, A joining process for joining the first part and the second part, Equipped with, The aforementioned preparation step is, The process of forming a first intermediate layer on the laser medium, The process involves forming a first metal layer containing a group 4 element or a group 6 element on the first intermediate layer, It has, In the joining process, the first part and the second part are joined via the first metal layer. The first intermediate layer includes a dielectric multilayer film formed on the laser medium that totally reflects the laser light generated or amplified by the laser medium. In the step of forming the first intermediate layer, the first intermediate layer is formed such that its thickness is greater than the seepage length of the evanescent wave generated by the reflection of light incident from the laser medium side by the dielectric multilayer film. A method for manufacturing optical elements.

11. The preparation step includes forming a second metal layer containing a Group 10 element on the heat sink. In the joining process, the first part and the second part are joined via the first metal layer and the second metal layer. A method for manufacturing an optical element according to claim 10.

12. The preparation step includes forming a layer on at least one of the first metal layer and the second metal layer that will become a second intermediate layer to be placed between the first metal layer and the second metal layer. A method for manufacturing an optical element according to claim 11.

13. In the joining process, the surface of the first component on the side that joins with the second component and the surface of the second component on the side that joins with the first component are subjected to surface activation treatment, and then the surface-activated first component and the second component are joined together. A method for manufacturing an optical element according to any one of claims 10 to 12.

14. The process further includes a step of surface-activating the surface of the first component that is joined to the second component and the surface of the second component that is joined to the first component. The preparation step further comprises the step of forming a second metal layer containing a group 10 element on the first metal layer, The second component is the heat sink, In the joining process, the first component and the second component are joined via the second metal layer. A method for manufacturing an optical element according to claim 10.

15. The step of forming the first intermediate layer is: The steps include forming the dielectric multilayer film on the laser medium, The steps include forming a non-metallic heat transfer layer on the dielectric multilayer film, A method for manufacturing an optical element according to any one of claims 10 to 12, comprising the above.

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