mirror

Abstract

To provide a mirror that reduces the electric field intensity on interfaces of a low refractive index layer and a high refractive index layer of a dielectric multilayer to improve its durability.SOLUTION: A mirror 1 comprises a base material 2, and an optical multilayer film 4 that is formed directly or indirectly on a base material surface Q being a surface of the base material 2. The optical multilayer film 4 has a main reflection structure part 10 and an adjustment structure part 12. The main reflection structure part 10 is an alternate film in which low refractive index layers L formed of low refractive index material and high refractive index layers H formed of high refractive index material are alternately arranged, and is arranged closer to the base material than the adjustment structure part. The adjustment structure part 12 is an alternate film in which low refractive index layers L formed of low refractive index material and a high refractive index layer H formed of high refractive index material are alternately arranged, and satisfies a predetermined condition related to the optical film thickness of the low refractive index layer L and high refractive index layer H with λ0 / 4 as a unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mirror that can be used for reflecting a laser beam, etc. [Background technology]

[0002] A known mirror for reflecting laser light is described in Patent Document 1 (WO 2019 / 167123). In this mirror, a dielectric multilayer film is formed on a substrate, in which low refractive index layers made of a dielectric low refractive index material and high refractive index layers made of a dielectric high refractive index material are alternately stacked. As described in

[0024] to

[0025] of Patent Document 1, in this dielectric multilayer film, in order to improve reflection efficiency, the optical film thickness of each of the low refractive index layer and the high refractive index layer is set to be one-fourth (QW; Quarter Wave) of the target wavelength (laser wavelength).

[0003] Recently, the use of high-power lasers has been increasing, and when the above-mentioned mirrors are used in optical systems for high-power lasers, the mirrors, especially the dielectric multilayer films which are thinner and weaker than other parts, tend to have a shorter lifespan than in the case of low-power lasers. Furthermore, in the above-mentioned dielectric multilayer film, because each optical film thickness is QW (QW structure), high reflectivity for light of the target wavelength can be obtained most efficiently, but there is room for improvement in durability. That is, in the QW structure, the electric field strength distribution of the laser takes a maximum value at each interface between the low refractive index layer and the high refractive index layer, resulting in a structure in which large energy is applied at each interface. Furthermore, as described in Patent Document 2 (Japanese Patent No. 2629693), it is believed that foreign matter is likely to be contained at each interface of a dielectric multilayer film during the film formation process, and that the electric field concentrates around the foreign matter, causing a local temperature rise and destroying the film. It has also been shown that by reducing the electric field strength at each interface, a more durable laser reflection mirror can be obtained. Furthermore, Non-Patent Document 1 discloses a structure in which the film thickness of a dielectric multilayer film is adjusted to reduce the electric field strength at each interface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 167123 [Patent Document 2] Patent No. 2629693 [Non-patent literature]

[0005] [Non-Patent Document 1] Shunli Chen and 3 others, "Effect of standing-wave field distribution on femosecond laser-induced damage of HfO2 / SiO2 mirror coating", Chinese Optics Letters, August 10, 2011, COL 9(8), p.083101-1~083101-4 Summary of the Invention [Problem to be solved by the invention]

[0006] In the dielectric multilayer films of Patent Document 2 and Non-Patent Document 1, the reduction in the electric field strength at each interface is insufficient, and there is room for improvement in durability. One of the main objects of the present invention is to provide a mirror with higher durability by reducing the electric field strength at each interface between a low refractive index layer and a high refractive index layer of a dielectric multilayer film or the like. [Means for solving the problem]

[0007] In order to achieve one of the above-mentioned main objects, the invention described in claim 1 includes a substrate and an optical multilayer film formed directly or indirectly on a substrate surface that is a surface of the substrate, the optical multilayer film having a main reflection structure and an adjustment structure, the main reflection structure being an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, and the main reflection structure is arranged on the substrate side relative to the adjustment structure, the adjustment structure being an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, and a target wavelength is λ0, a pair number is x which is a number counted from the substrate side for pairs of a low refractive index layer and a high refractive index layer adjacent thereto on the opposite substrate side, and a total number of pairs which is x e The optical thicknesses of the low refractive index layer and the high refractive index layer at x in units of λ0 / 4 are respectively represented as D L (x), D H (x), and the refractive indices of the low refractive index layer, the high refractive index layer, and the incident medium are n L , n H , n0, and the physical thicknesses of the low refractive index layer and the high refractive index layer at x are d L (x), d H (x), and the reference values ​​when considering oblique incidence in the low refractive index layer L and the high refractive index layer H are k L , k H and the incident angle of the laser LA is θ0, the present invention is characterized in that all of the following formulas (10) to (19) are satisfied. The invention described in claim 2 is the above invention, wherein the main reflection structure has a number of low refractive index layers (however, when a low refractive index layer is arranged as the first layer counted from the substrate side, this first layer is not counted) of c L , the number of high refractive index layers H is c H Counting from the substrate 2 side, m(=1,...,c L +c H The optical thicknesses of the low refractive index layer and the high refractive index layer in the 2nd layer in units of λ0 / 4 are respectively represented by D L (m), D H (m), and the physical thickness of the mth layer is d when the low refractive index layer L L (m), and d in the case of the high refractive index layer H. H(m), and the sums in each low refractive index layer and each high refractive index layer are respectively Σ L , Σ H Then, the present invention is characterized by satisfying all of the following formulas (1) to (9). The invention described in claim 3 is characterized in that, in the above invention, x is 13 or more. The invention described in claim 4 is characterized in that, in the above invention, x is 28 or less. In order to achieve one of the above-mentioned main objects, the invention described in claim 5 comprises a substrate and an optical multilayer film formed directly or indirectly on a substrate surface that is a surface of the substrate, the optical multilayer film being an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, and the optical multilayer film is All The maximum value of the electric field strength at the layer interface is Any 0.4 or less, and the reflectance of the optical multilayer film at the target wavelength λ0 for a laser beam of the target wavelength λ0 incident at an incident angle θ0 is 99.5% or more. The electric field strength is calculated by the square of the absolute value of the ratio of the electric field in the optical multilayer film to the electric field of the incident light (|electric field in the optical multilayer film / electric field of the incident light| 2 ) In order to achieve one of the above-mentioned main objects, the invention described in claim 6 comprises a substrate and an optical multilayer film formed directly or indirectly on a substrate surface that is a surface of the substrate, the optical multilayer film being an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, and the optical multilayer film is All At the layer interface The above The expected maximum value of the electric field strength is Any The optical multilayer film is characterized in that the expected reflectance at the target wavelength λ0 of the optical multilayer film for a laser having the target wavelength λ0 incident at an incident angle θ0 is 0.28 or less, and when a manufacturing error of ±1% is taken into consideration, the expected reflectance at the target wavelength λ0 of the optical multilayer film is 99.5% or more. [Effects of the Invention]

[0008] One of the main effects of the present invention is that it reduces the electric field strength at each interface between a low refractive index layer and a high refractive index layer of a dielectric multilayer film or the like, thereby providing a mirror with higher durability. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a mirror according to the present invention. [Figure 2] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 1-1. [Figure 3] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 1-2. [Figure 4] 1 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 1-1. [Figure 5] 1 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 1-2. [Figure 6] 1 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Examples 1-3. [Figure 7] 1 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Examples 1-4. [Figure 8] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 1-1. [Figure 9] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Comparative Example 1-2. [Figure 10] 1 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Example 1-1. [Figure 11] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 1-2. [Figure 12] 1 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Examples 1-3. [Figure 13] 1 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Examples 1-4. [Figure 14] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 1-1. [Figure 15] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 1-2. [Figure 16] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 1-1. [Figure 17] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 1-2. [Figure 18] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 1-3. [Figure 19] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Examples 1-4. [Figure 20] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 2-1. [Figure 21] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 2-2. [Figure 22] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 2-1. [Figure 23] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 2-2. [Figure 24] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 2-3. [Figure 25] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 2-4. [Figure 26] 10 is a graph showing the spectral reflectance distribution of s-polarized light in a wavelength range including a target wavelength in the optical multilayer coating according to Comparative Example 2-1. [Figure 27] 10 is a graph showing the spectral reflectance distribution of s-polarized light in a wavelength range including a target wavelength in an optical multilayer coating according to Comparative Example 2-2. [Figure 28] 10 is a graph showing the spectral reflectance distribution of s-polarized light in a wavelength range including a target wavelength in the optical multilayer coating according to Example 2-1. [Figure 29]10 is a graph showing the spectral reflectance distribution of s-polarized light in a wavelength range including a target wavelength in the optical multilayer coating according to Example 2-2. [Figure 30] 10 is a graph showing the spectral reflectance distribution of s-polarized light in a wavelength range including a target wavelength in the optical multilayer coating according to Example 2-3. [Figure 31] 10 is a graph showing the spectral reflectance distribution of s-polarized light in a wavelength range including a target wavelength in an optical multilayer coating according to Example 2-4. [Figure 32] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Comparative Example 2-1. [Figure 33] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Comparative Example 2-2. [Figure 34] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Example 2-1. [Figure 35] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Example 2-2. [Figure 36] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Example 2-3. [Figure 37] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Example 2-4. [Figure 38] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 3-1. [Figure 39] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 3-2. [Figure 40] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 3-1. [Figure 41] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 3-2. [Figure 42] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 3-3. [Figure 43] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 3-4. [Figure 44]10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 3-1. [Figure 45] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 3-2. [Figure 46] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Example 3-1. [Figure 47] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 3-2. [Figure 48] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 3-3. [Figure 49] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 3-4. [Figure 50] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 3-1. [Figure 51] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 3-2. [Figure 52] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 3-1. [Figure 53] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 3-2. [Figure 54] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 3-3. [Figure 55] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 3-4. [Figure 56] 4 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 4-1. [Figure 57] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 4-2. [Figure 58] 4 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 4-1. [Figure 59]10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 4-2. [Figure 60] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 4-3. [Figure 61] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 4-4. [Figure 62] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 4-1. [Figure 63] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 4-2. [Figure 64] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 4-1. [Figure 65] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 4-2. [Figure 66] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 4-3. [Figure 67] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 4-4. [Figure 68] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 4-1. [Figure 69] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 4-2. [Figure 70] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 4-1. [Figure 71] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 4-2. [Figure 72] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 4-3. [Figure 73] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 4-4. [Figure 74]10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 5-1. [Figure 75] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 5-2. [Figure 76] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 5-3. [Figure 77] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 5-4. [Figure 78] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 5-5. [Figure 79] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 5-1. [Figure 80] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 5-2. [Figure 81] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 5-3. [Figure 82] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 5-4. [Figure 83] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 5-5. [Figure 84] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 5-6. [Figure 85] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 5-1. [Figure 86] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 5-2. [Figure 87] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in an optical multilayer film according to Comparative Example 5-3. [Figure 88] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in an optical multilayer film according to Comparative Example 5-4. [Figure 89]10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in an optical multilayer film according to Comparative Example 5-5. [Figure 90] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 5-1. [Figure 91] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 5-2. [Figure 92] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 5-3. [Figure 93] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 5-4. [Figure 94] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 5-5. [Figure 95] 10 is a graph showing the spectral reflectance distribution in the wavelength range of s-polarized light including the target wavelength in the optical multilayer coating according to Example 5-6. [Figure 96] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 5-1. [Figure 97] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 5-2. [Figure 98] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 5-3. [Figure 99] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 5-4. [Figure 100] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 5-5. [Figure 101] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 5-1. [Figure 102] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 5-2. [Figure 103] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 5-3. [Figure 104]10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 5-4. [Figure 105] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 5-5. [Figure 106] 10 is a graph showing the electric field intensity distribution of s-polarized light in the optical multilayer film according to Example 5-6. [Figure 107] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 6-1. [Figure 108] 6 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 6-1. [Figure 109] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 6-2. [Figure 110] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 6-3. [Figure 111] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 6-4. [Figure 112] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 6-5. [Figure 113] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 6-1. [Figure 114] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 6-1. [Figure 115] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 6-2. [Figure 116] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 6-3. [Figure 117] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 6-4. [Figure 118] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 6-5. [Figure 119]10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 6-1. [Figure 120] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 6-1. [Figure 121] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 6-2. [Figure 122] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 6-3. [Figure 123] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 6-4. [Figure 124] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 6-5. [Figure 125] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 7-1. [Figure 126] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Comparative Example 7-2. [Figure 127] 10 is a graph showing the optical film thickness of each layer in the optical multilayer film according to Example 7-1. [Figure 128] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer film according to Comparative Example 7-1. [Figure 129] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Comparative Example 7-2. [Figure 130] 10 is a graph showing the spectral reflectance distribution in a wavelength range including a target wavelength in the optical multilayer coating according to Example 7-1. [Figure 131] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 7-1. [Figure 132] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Comparative Example 7-2. [Figure 133] 10 is a graph showing the electric field intensity distribution in the optical multilayer film according to Example 7-1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, examples of embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these examples.

[0011] As shown in FIG. 1, a mirror 1 according to the present invention includes a substrate 2 and an optical multilayer film 4. The substrate 2 has a substrate surface Q on which an optical multilayer film 4 is directly formed. The mirror 1 reflects a laser beam LA of a predetermined wavelength that has passed through a medium (e.g., air) at the optical multilayer film 4 laminated on the substrate surface Q. The optical multilayer film 4 may be formed indirectly on the substrate surface Q, which is the surface of the substrate 2, via another film such as an adhesive film of the optical multilayer film 4. Also, a different film such as a protective film may be disposed on the outside (medium side, opposite substrate side) of the optical multilayer film 4. The other film and the other film may be a single-layer film or a multilayer film. The configuration of the optical multilayer film 4 may include at least one of the other film and the other film.

[0012] The base material 2 may or may not have light-transmitting properties. The material of the substrate 2 is not particularly limited, and may be, for example, a non-metallic material such as glass, crystal, ceramics, or resin. The shape of the substrate 2 is not particularly limited, and may be, for example, a parallel plate, a wedge, or a prism.

[0013] The optical multilayer film 4 contributes to the reflection of the laser LA, and is an inorganic multilayer film using two or more types of dielectric materials, and is a dielectric multilayer film. The optical multilayer film 4 is formed on a part or the whole of at least one surface of the substrate 2 . The optical multilayer film 4 includes one or more low refractive index layers L and one or more high refractive index layers H. In the optical multilayer film 4, the low refractive index layers L and the high refractive index layers H are preferably arranged alternately. The optical multilayer film 4 may further include a medium refractive index layer. The design of the optical multilayer film 4 can be changed by changing design elements such as the number and materials of the high refractive index layers H and low refractive index layers L (and the medium refractive index layers), and increasing or decreasing the thickness of each layer (physical film thickness or optical film thickness of the layer).

[0014] The high refractive index layer H is formed from a high refractive index material such as zirconium oxide (ZrO2), titanium oxide (TiO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), hafnium oxide (HfO2), lanthanum oxide (La2O3), silicon (Si), or praseodymium oxide (Pr2O3), or a mixture of two or more of these. The low refractive index layer L is formed from a low refractive index material such as silicon oxide (SiO2), aluminum oxide (Al2O3), calcium fluoride (CaF2), magnesium fluoride (MgF2), a combination of aluminum oxide and praseodymium oxide (Al2O3-Pr2O3), a combination of aluminum oxide and lanthanum oxide (Al2O3-La2O3), or a combination of aluminum oxide and tantalum oxide (Al2O3-Ta2O5), or a mixture of two or more of these. The medium refractive index layer is formed from a medium refractive index material such as Al2O3, Pr2O3, La2O3, Al2O3-Pr2O3, or Al2O3-La2O3. For example, two or more materials may be selected from the above-mentioned high refractive index materials to form the high refractive index layer H. The same applies to the low refractive index layer L.

[0015] The low refractive index layer L and high refractive index layer H (and the medium refractive index layer) of the optical multilayer film 4 are formed by, for example, physical vapor deposition, more specifically, vacuum deposition, ion-assisted deposition, ion plating, sputtering, or the like. The optical multilayer film 4 may be formed on multiple surfaces of the substrate 2. That is, the substrate 2 may have multiple substrate surfaces Q on which the optical multilayer film 4 is formed. For example, the optical multilayer film 4 may be formed on both the front and back surfaces of the substrate 2 that is a parallel plate, a wedge, a concave surface, a convex surface, or a prism.

[0016] The optical multilayer film 4 has a primary reflection structure 10 and an adjustment structure 12 . The main reflection structure 10 is disposed closer to the substrate 2 than the adjustment structure 12 is. The main reflective structure 10 and the adjustment structure 12 are adjacent to each other. A single-layer or multi-layer intermediate structure may be disposed between the main reflective structure 10 and the adjustment structure 12.

[0017] The primary reflection structure 10 has a QW structure or a structure similar to a QW structure, that is, the primary reflection structure 10 has one or more low refractive index layers L, each having an optical film thickness of about 1 / 4 of the target wavelength λ0, and one or more high refractive index layers H, each having an optical film thickness of about 1 / 4 of the target wavelength λ0, arranged alternately. The layer in the primary reflection structure 10 closest to the substrate 2 may be a low refractive index layer L or a high refractive index layer H. When adhesion to the substrate 2 or adjacent layers is more important, it is preferable that the layer closest to the substrate 2 be a low refractive index layer L. The layer closest to the medium (adjustment structure 12 side) in the main reflection structure 10 is a high refractive index layer H. In a structure based on a QW structure, the optical thickness of at least any low-refractive-index layer L may be 0.8 times (80%) to 1.2 times (120%), or 0.9 times (90%) to 1.1 times (110%) of the target wavelength λ. Furthermore, when the primary reflection structure 10 has two or more low-refractive-index layers L, the average optical thickness of the low-refractive-index layers L may be 0.95 times (95%) to 1.02 times (102%), or 0.98 times (98%) to 1.01 times (101%) of the target wavelength λ. The same applies to the optical thickness of at least any high-refractive-index layer H. The number of layers in the primary reflection structure 10 is preferably 15 or more, and more preferably 19 or more, from the viewpoint of obtaining sufficient reflectance for the laser LA of the target wavelength λ0.

[0018] The following are mathematical expressions expressing the above matters related to the main reflection structure 10. In order to express the mathematical expressions more simply, it is assumed that one type of low refractive index material and one type of high refractive index material are used in the main reflection structure 10.

[0019]

number

[0020] That is, the number of low refractive index layers L in the main reflection structure 10 (however, when a low refractive index layer L is arranged in the first layer, the first layer is regarded as an extended portion of the base material 2 and is not counted) is set to c L , the number of high refractive index layers H is c H The target wavelength (which can also be considered as the design wavelength because it is designed to reflect light of the target wavelength) is λ0, and counting from the substrate 2 side, m (= 1, . . . , c L +c H The optical thicknesses of the low refractive index layer L and the high refractive index layer H in the 2nd layer are expressed in units of λ0 / 4 as D L (m), D H (m), and the refractive indices of the low refractive index layer, high refractive index layer, and incident medium are n L , n H , n0, and the physical film thickness of the mth layer counted from the x substrate 2 side is d in the case of the low refractive index layer L L (m), d in the case of the high refractive index layer H H (m), and the reference values ​​when considering oblique incidence in the low refractive index layer L and the high refractive index layer H are k L , k H The incident angle of the laser LA to the mirror 1 is θ0, and the sums at each low refractive index layer L and each high refractive index layer H are sequentially calculated as Σ L , Σ H Then, D L (m), D H For (m), equations (1) and (2) hold true, and k L , k H Formulas (3) and (4) hold true for the above, respectively. Furthermore, formulas (5) to (9) are given as preferable conditions for the main reflection structure 10. The incident angle θ0 is an angle with respect to a virtual perpendicular line VA of the optical multilayer film 4. When the incident angle θ0 is 0° (when the laser LA is incident perpendicularly to the optical multilayer film 4), k L , k H and (6) to (9) are both 1, which simplifies the equations (6) to (9). In addition, the layer in the main reflection structure 10 closest to the substrate 2 can be regarded as always being the high refractive index layer H, and the one low refractive index layer L adjacent to the high refractive index layer H can be regarded as not being part of the main reflection structure 10.

[0021] The adjustment structure 12 is provided to suppress a decrease in reflectance of the laser LA having the target wavelength λ0, while suppressing the electric field intensity at each interface of the optical multilayer film 4, thereby improving durability. The layer in the adjustment structure 12 closest to the substrate 2 (closer to the main reflection structure 10) is a low refractive index layer L. The optical film thickness of the low refractive index layer L is the same as the optical film thickness of the low refractive index layer L in the main reflection structure 10. The optical film thickness of the high refractive index layer H adjacent to the low refractive index layer L on the medium side is the same as the optical film thickness of the low refractive index layer L in the main reflection structure 10. The pair number x indicating the pair of the low refractive index layer L closest to the substrate 2 in the adjustment structure 12 and the high refractive index layer H adjacent thereto is set to 1. The layer closest to the medium in the adjustment structure 12 is a high refractive index layer H. A low refractive index layer L may be disposed on the medium side of the high refractive index layer H as a protective film that is not included in the adjustment structure 12. From the viewpoint of easier manufacturing, it is preferable that the material of this low refractive index layer L is the same as the material of the other low refractive index layers L. The pair number x of the pair of the low refractive index layer L adjacent to the pair number x=1 on the medium side and the high refractive index layer H adjacent thereto is set to 2, and similarly, the pair numbers x=3, 4, . . . , x e The pair number closest to the medium in the adjustment structure 12 is x e It is said that. x e indicates the total number of pairs, which is the total number of pairs present in the adjustment structure portion 12. Total number of pairs in the adjustment structure 12 x e The total number of pairs x is preferably 7 or more and 38 or less, and more preferably 13 or more and 28 or less. eIf the lower limit of x is too small, it is difficult to obtain a design that sufficiently suppresses the electric field strength at each interface while suppressing the decrease in reflectivity. e If the upper limit of is too large, the design and manufacturing will be time-consuming, and there will be a relatively large possibility that the expected performance will not be obtained due to the superposition of manufacturing errors.

[0022] The optical thickness of the low refractive index layer L in the adjustment structure 12 increases toward the medium side. That is, the optical thickness of the low refractive index layer L increases as the pair number x to which the low refractive index layer L belongs increases. The increase in the optical thickness of the low refractive index layer L toward the x increasing side is larger toward the substrate side and smaller toward the medium side. e ) the optical thickness D of the low refractive index layer L L (x) complies with the specified conditions described below.

[0023] The optical thickness of the high refractive index layer H in the adjustment structure 12 decreases toward the medium side. That is, the optical thickness of the high refractive index layer H decreases as the pair number x to which the high refractive index layer H belongs increases. The decrease in the optical thickness of the high refractive index layer H toward the x-increasing side is larger toward the substrate side and smaller toward the medium side. e ) the optical thickness D of the high refractive index layer H H (x) complies with the specified conditions described below.

[0024] Such optical thickness D L (x),D H By including the adjustment structure 12 having (x) in the optical multilayer film 4, the maximum value (peak) of the electric field strength is shifted from each interface in the electric field strength distribution when the laser LA of the target wavelength λ0 is incident on the optical multilayer film 4, and the electric field strength at each interface is suppressed. In addition, the maximum value of the electric field strength at each interface is also suppressed.

[0025] The mathematical expressions relating to the adjustment structure 12 are shown below. Note that, in order to express the mathematical expressions more simply, it is assumed that one type of low refractive index material and one type of high refractive index material are used in the adjustment structure 12.

[0026]

number

[0027] That is, first, as mentioned above, the total number of pairs x e is preferably 7 or more and 38 or less, and therefore, as a preferable condition for the adjustment structure 12, the following formula (10) holds. Next, the physical thicknesses of the low refractive index layer L and the high refractive index layer H in pair number x are sequentially determined as d L (x), d L (x), the optical thickness D of the low refractive index layer L L (x), and the optical thickness D of the high refractive index layer H H (x) is expressed by equations (11) and (12), respectively. The optical thickness D of the low refractive index layer L L (x) is the optical thickness D of the low refractive index layer L expressed by formula (13) L Function f that defines (x) L It is ideal to follow (x) from the viewpoint of suppressing the decrease in reflectance and suppressing the electric field strength at the interface. H (x) is the optical thickness D of the high refractive index layer H expressed by formula (14) H Function f that defines (x) H It is ideal to follow (x) from the viewpoint of suppressing the decrease in reflectivity and suppressing the electric field strength at the interface. In such an ideal case, D L (x) / f L (x) becomes 1, and D H (x) / f H (x) becomes 1. Furthermore, from the viewpoint of suppressing the decrease in reflectance and suppressing the electric field strength at the interface while allowing for a certain degree of manufacturing error, the optical film thickness D L (x) may vary to some extent from the ideal value (reference value) expressed by formula (13), and the allowable range of deviation is expressed by formula (15) (96.3% to 112% of the reference value). H(x) may vary somewhat from the ideal value (reference value) expressed by formula (14), and the allowable range of deviation is expressed by formula (16) (53.2% to 128% of the reference value). However, from the above viewpoint, it is preferable to prevent the optical film thicknesses of the low refractive index layer L and the high refractive index layer H in the same pair number x from deviating too much, and this condition is expressed by formula (17) as a condition regarding the range of the average value of the optical film thicknesses belonging to the same pair number x (the average value is 1.005 to 1.069). Equations (18) and (19) are the same as equations (3) and (4), respectively.

[0028] When all of the formulas (10) to (19) are satisfied, the optical multilayer film 4 having the adjustment structure 12 has the following characteristics for the laser beam LA having the target wavelength λ0 incident at an incident angle θ0. That is, the electric field strength is 0.4 or less at all interfaces of the optical multilayer film 4 (the primary reflection structure 10 and the adjustment structure 12). Furthermore, the reflectivity is 99.5% or more.

[0029] Also, x in equation (10) e The lower limit of x is set to 13 instead of 7, and e The upper limit of x is set to 28 instead of 38, i.e., the total number of pairs x e is between 13 and 28 (13≦x e ≦28), when all of the formulas (11) to (19) are satisfied, the optical multilayer film 4 having the adjustment structure 12 has the following characteristics for the laser beam LA having the target wavelength λ0 incident at an incident angle θ0. That is, the expected value of the electric field intensity is 0.280 or less at all interfaces of the optical multilayer film 4 (the primary reflection structure 10 and the adjustment structure 12). Furthermore, the expected reflectance is 99.5% or more. The expected value is obtained by calculating values ​​such as electric field strength for each film thickness randomly obtained for each trial, and averaging the values ​​over a sufficient number of trials, while setting the distribution of the probability of occurrence of the formation ratio (= formed film thickness / design film thickness × 100[%]), which is the ratio of the formed film thickness to the design value, to a predetermined distribution. The predetermined distribution is, for example, a normal distribution in which the occurrence probability is greatest when the formation ratio = 100%, and the occurrence probability decreases as the formation ratio deviates from 100%. Such a normal distribution is a distribution in which manufacturing errors with a formation ratio close to 100% appear relatively frequently, and manufacturing errors with a formation ratio far from 100% appear relatively rarely, and is consistent with actual film manufacturing. [Example]

[0030] Next, examples according to the above-described embodiment of the present invention will be described. However, the examples do not limit the scope of the present invention. Furthermore, depending on how the present invention is interpreted, an example may be essentially a comparative example that falls outside the scope of the present invention, or a comparative example may be essentially an example that falls within the scope of the present invention.

[0031] [1064nm normal incidence · total number of pairs x e Changes - Example 1, Comparative Example 1 As Comparative Example 1-1, a mirror having an optical multilayer film including only a portion (QW structure) corresponding to the primary reflection structure 10 and a protective film (not including the adjustment structure 12) on one surface (substrate surface Q) of a parallel plate substrate 2 (substrate) was used. The target wavelength λ0 in air was 1064 nm (nanometers), and the incident angle θ0 was 0° (normal incidence; k L =k H It was created through simulation, taking into account the reflection of the laser LA (=1). The medium is air, and the refractive index n0 of the medium at the target wavelength λ0 (the same applies to the refractive index hereinafter) is 1.000. The substrate is made of quartz glass, and its refractive index is 1.453. As shown in Figure 2 and Table 1 below, the optical multilayer film is an alternating film of low refractive index layers L (SiO2 layers) made of SiO2 and high refractive index layers H (HfO2 layers) made of HfO2, and has a total of 21 layers. The layer (first layer) closest to the substrate in the optical multilayer film is the SiO2 layer. The refractive index n of the SiO2 layer is L The refractive index of the HfO2 layer is 1.474. H The optical thickness D of all SiO2 layers except for the layer closest to the medium (21st layer) is 1.954. L (m) is set to 1. The 21st SiO2 layer is a protective film, and its optical thickness is set to 2. In addition, in all HfO2 layers, the optical thickness D H (m) is set to 1. Total number of pairs x in the optical multilayer coating of Comparative Example 1-1 e can be said to be 0.

[0032] [Table 1]

[0033] In addition, as Comparative Example 1-2, on one side of the same substrate as Comparative Example 1-1, the same portion corresponding to the main reflection structure 10 and the same protective film as Comparative Example 1-1, and the total number of pairs x e A mirror having an optical multilayer film including a portion corresponding to the adjustment structure 12 where .lambda.=3 was formed by simulation. 3 and Table 1, the optical multilayer film of Comparative Example 1-2 has a total of 27 layers, and the 1st to 20th layers are the same as those of Comparative Example 1-1. The 21st and 22nd layers of the optical multilayer film of Comparative Example 1-2 are the SiO2 layer (L) and the HfO2 layer (H) in the pair number x=1, and the optical film thicknesses D L (x),D H (x). In particular, the optical thickness D L (x)=f L (x), and the optical thickness D H (x)=f H Furthermore, the 23rd and 24th layers of the optical multilayer film of Comparative Example 1-2 are an SiO2 layer and an HfO2 layer in pair number x=2, and the optical film thicknesses DL (x),D H (x), in particular, the optical thickness D L (x)=f L (x), and the optical thickness D H (x)=f H In addition, the 25th and 26th layers of the optical multilayer film of Comparative Example 1-2 are an SiO2 layer and an HfO2 layer in pair number x=3, and the optical film thicknesses D L (x),D H (x), in particular, the optical thickness D L (x)=f L (x), and the optical thickness D H (x)=f H (x) Furthermore, the 27th layer of the optical multilayer film of Comparative Example 1-2 is an SiO2 layer as a protective film. Hereinafter, Comparative Examples 1-1 and 1-2 may be collectively referred to as Comparative Example 1.

[0034] On the other hand, Example 1-1 is the same as Comparative Example 1-2, and the total number of pairs of the adjustment structure portion 12 is x e Mirror 1 was formed in the same manner except that the number of atoms was changed from 3 to 7. That is, as shown in FIG. 4 and Table 2 below, the optical multilayer film of Example 1-1 has a total of 35 layers, of which the 1st to 26th layers are the same as those of Comparative Example 1-1. The 27th to 34th layers correspond to pair numbers x=4 to 7, and the optical thickness of each layer is f L (x),f H The 21st to 34th layers are the adjustment structure 12, and as shown in FIG. 4, the optical thickness of each SiO2 layer is f L (x) and the optical thickness of each HfO2 layer is f H Draw (x). f L (x) and f H When the (x) are overlapped, they form the shape of a crocodile's mouth when viewed from the side. Furthermore, the 35th layer is an SiO2 layer that serves as a protective film.

[0035] [Table 2]

[0036] Similarly, the total number of pairs x e was changed to 13 to form Example 1-2. That is, as shown in FIG. 5 and Table 2, the optical multilayer film of Example 1-2 has a total of 47 layers, of which the 1st to 34th layers are the same as those of Example 1-1. The 35th to 46th layers correspond to pair numbers x=8 to 13, and the optical thickness of each layer is f L (x),f H The 21st to 46th layers are the adjustment structure 12, and the optical thickness of each SiO2 layer therein is f L (x) and the optical thickness of each HfO2 layer is f H Draw (x). Furthermore, the 47th layer is an SiO2 layer that serves as a protective film.

[0037] Furthermore, the total number of pairs x e was changed to 28 to form Examples 1-3. 6 and Table 3 below, the optical multilayer film of Example 1-3 has a total of 77 layers, of which the 1st to 46th layers are the same as those of Example 1-2. Due to space limitations, the 3rd to 46th layers are omitted in Table 3. The 47th to 76th layers correspond to pair numbers x=14 to 28, and the optical thickness of each layer is f L (x),f H The 21st to 76th layers are the adjustment structure 12, and the optical thickness of each SiO2 layer therein is f L (x) and the optical thickness of each HfO2 layer is f H Draw (x). Furthermore, the 77th layer is an SiO2 layer as a protective film.

[0038] [Table 3]

[0039] Furthermore, the total number of pairs x e was changed to 38 to form Examples 1-4. 7 and Table 3, the optical multilayer film of Example 1-4 has a total of 97 layers, of which the 1st to 76th layers are the same as those of Example 1-3. Due to space limitations, the 3rd to 46th layers are omitted in Table 3, and the 91st and subsequent layers are shifted to the left. The 77th to 96th layers correspond to pair numbers x=29 to 38, and the optical thickness of each layer is f L (x),f H The 21st to 96th layers are the adjustment structure 12, and the optical thickness of each SiO2 layer therein is f L (x) and the optical thickness of each HfO2 layer is f H Draw (x). Furthermore, the 97th layer is an SiO2 layer that serves as a protective film. Hereinafter, Examples 1-1 to 1-4 may be collectively referred to as Example 1.

[0040] Figures 8 to 13 show the spectral reflectance distributions in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident on the optical multilayer films of Comparative Examples 1-1 to 1-2 and the optical multilayer films 4 of Examples 1-1 to 1-4 at an incident angle θ0 = 0°, respectively. In Comparative Example 1-1, the reflectance at the target wavelength λ0 is 99.0%, which is less than 99.5%, and the reflectance of the laser LA at the target wavelength λ0 is relatively poor. On the other hand, in all of Comparative Example 1-2 and Examples 1-1 to 1-4, the reflectance at the target wavelength λ0 is close to 100%, and Comparative Example 1-2 and Examples 1-1 to 1-4 all sufficiently reflect the laser LA of the target wavelength λ0. Furthermore, in the order of Comparative Examples 1-1 to 1-2 and Examples 1-1 to 1-4 (in the order of increasing number of layers of the optical multilayer film (adjustment structure 12)), the wavelengths associated with the minimum values ​​of reflectance adjacent to the target wavelength λ0 on the short wavelength side are closer to the target wavelength λ0. Therefore, from the viewpoint of placing importance relatively on the reflectance at the target wavelength λ0, the total number of pairs x of the adjustment structure 12 is e is preferably 38 or less, more preferably 28 or less.

[0041] The electric field intensity distributions when a laser LA with a target wavelength λ0=1064 nm is incident at an incident angle θ0=0° on the optical multilayer films of Comparative Examples 1-1 to 1-2 and the optical multilayer films 4 of Examples 1-1 to 1-4 are shown in Figures 14 to 19, respectively. In Comparative Example 1-1, the maximum value of the electric field strength is located at the interface between the odd-numbered layer and the even-numbered layer (the odd-numbered interface counting from the substrate side, the odd-numbered vertical scale line counting from the leftmost vertical axis side in Figure 14), and the maximum value of the electric field strength at all interfaces related to 1st to 20th is 1.02 at the interface between the 19th layer and the 20th layer (19th). In Comparative Example 1-2, the electric field strength has maximum values ​​at the odd-numbered interfaces up to the 19th layer, but at the 21st and subsequent interfaces, the electric field strength maximum values ​​are shifted toward the low refractive index layer side from those interfaces. The maximum electric field strength at all interfaces is 0.704 at the 25th interface. In Comparative Example 1-1, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is less than 99.5%, and the maximum value of the electric field strength at all interfaces of the optical multilayer film exceeds 0.4. In Comparative Example 1-2, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, but the maximum value of the electric field strength at all interfaces of the optical multilayer film exceeds 0.4.

[0042] In Example 1-1, at the 21st and higher interfaces, the maximum value of the electric field strength is shifted toward the low refractive index layer side from that interface. The electric field strength at the interfaces up to the 20th layer (main reflection structure 10) is larger than the surrounding area because the maximum value of the electric field strength distribution is located there, but this is sufficiently suppressed by the placement of the 21st and higher layers (adjustment structure 12) on the air side. The maximum value of the electric field strength at all interfaces is 0.343 at the 29th interface. In Example 1-2, at the 21st and subsequent interfaces, the maximum value of the electric field strength is shifted toward the low refractive index layer side from the interface. The maximum value of the electric field strength at all interfaces is 0.199 at the 29th interface. In Example 1-3, the maximum value of the electric field strength is shifted toward the low refractive index layer at the 21st and higher interfaces. The maximum value of the electric field strength at all interfaces is 0.095 at the 59th, 61st, and 63rd interfaces. In Examples 1-4, the maximum value of the electric field strength is shifted toward the low refractive index layer at the 21st and higher interfaces. The maximum value of the electric field strength at all interfaces is 0.074 at the 59th, 61st, and 63rd interfaces. In Example 1, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, and the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 is 0.4 or less.

[0043] Furthermore, as shown in Table 4 below, when manufacturing errors are simulated in Comparative Example 1 and Example 1, the expected values ​​of the maximum electric field strength at all interfaces are 1.042, 0.704, 0.351, 0.223, 0.189, and 0.348 for Comparative Examples 1-1 to 1-2 and Examples 1-1 to 1-4, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 98.97, 99.69, 99.85, 99.91, 99.93, and 99.83, respectively.

[0044] [Table 4]

[0045] The manufacturing error was simulated here as follows. That is, a normal distribution was assumed with a mean value of 1 and a standard deviation σ of 0.333, with the horizontal axis representing the formation ratio (= formed physical film thickness / design physical film thickness × 100 [%]) of the formed physical film thickness to the intended physical film thickness (design physical film thickness) and the vertical axis representing the probability density of the formation ratio. The highest probability density appears when the formation ratio is 100%, and the probability density decreases as the formation ratio deviates from 100%. This distribution clearly represents the case where a manufacturing error of ±1% occurs on average with respect to the designed physical film thickness. The designed physical film thicknesses of Comparative Example 1 and Example 1 are as shown in Tables 1 to 3 above. Then, for each trial, the formation ratio of the high refractive index layer H and the formation ratio of the low refractive index layer L were determined randomly based on the occurrence probability according to this normal distribution, and the maximum value of the electric field intensity at all interfaces and the reflectance at the target wavelength λ0 were calculated when all the high refractive index layers H and all the low refractive index layers L belonging to the optical multilayer film (main reflection structure 10 and adjustment structure 12) were formed at those formation ratios. Such trials are realistic in light of the fact that in physical vapor deposition for forming alternating films of two materials, targets (evaporation materials) for the high refractive index layer H and targets for the low refractive index layer L are evaporated alternately and in the same chamber in the same way. This trial was repeated 500 times, and the maximum value of the electric field strength at all interfaces was calculated for each trial. The average value was taken as the expected value of the maximum value of the electric field strength at the interfaces. The average value of the reflectance at the target wavelength λ0 was taken as the expected value of the reflectance at the target wavelength λ0.

[0046] In Comparative Examples 1-1 to 1-2 and Examples 1-1 to 1-3, the expected reflectance at the target wavelength λ0 is the same as the reflectance at the target wavelength λ0 (the reflectance when all formation ratios are 100%, i.e., when all are as designed). In Example 1-4, the difference (degree of decrease) between the expected reflectance at the target wavelength λ0 and the reflectance at the target wavelength λ0 is slightly larger. This is because, when the number of layers of the adjustment structure 12 increases, as in Example 1-4, the minimum value of reflectance adjacent to the target wavelength λ0 on the shorter wavelength side occurs near the target wavelength λ0 due to the influence of manufacturing errors. Furthermore, among Example 1, in Examples 1-1 to 1-3, the difference (degree of increase) between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface (when all formation ratios are 100%, i.e., when all are as designed) is small. On the other hand, in Example 1-4, the difference between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface is large. This corresponds to the fact that when the number of layers of the adjustment structure 12 increases, as in Example 1-4, the deviation from 100% formation ratio, i.e., the influence of manufacturing errors, accumulates, and the electric field strength at the interface does not reach the intended maximum value. In addition, among Examples 1-1 to 1-3, Examples 1-2 and 1-3 (total number of pairs x e=13,28), the maximum and expected values ​​of the electric field strength at the interface are low and stable. e In the range of =13 to 28, when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field intensity at the interface for a laser beam LA of target wavelength λ0 incident at an incident angle θ0 is 0.280 or less. In this case, the expected value of reflectivity is 99.5% or more.

[0047] [1064nm 45° oblique incidence · total number of pairs x e Changes - Example 2, Comparative Example 2 As comparative examples 2-1 and 2-2, as shown in Figures 20 and 21 and Table 5 below, the same as comparative examples 1-1 and 1-2 were created, respectively, except that the incident angle θ0 of the laser LA was changed to 0° with 45° in mind. As shown in Figures 22 and 23 and Table 6 below, Examples 2-1 to 2-2 were created in the same order as Examples 1-1 to 1-2, except that the incident angle θ0 of the laser LA was changed to 0° with 45° in mind. As Examples 2-3 to 2-4, as shown in Figures 24 and 25 and Table 7 below, the same as Examples 1-3 to 1-4 were created in order, except that the incident angle θ0 of the laser LA was changed to 0° with 45° in mind. In Example 2 and Comparative Example 2, the incident light is 45° obliquely incident, so k L =1.140, and k H =1.073.

[0048] [Table 5]

[0049] [Table 6]

[0050] [Table 7]

[0051] Figures 26 to 31 show the spectral reflectance distributions of s-polarized light in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident on the optical multilayer films of Comparative Examples 2-1 to 2-2 and the optical multilayer films 4 of Examples 2-1 to 2-4 at an incident angle θ0 = 45°. In both Comparative Example 2 and Example 2, the reflectance of s-polarized light at the target wavelength λ0 is close to 100%, and both Comparative Example 2 and Example 2 sufficiently reflect the laser LA of the target wavelength λ0. Furthermore, in the order of Comparative Examples 2-1 to 2-2 and Examples 2-1 to 2-4 (in the order of increasing number of layers of the adjustment structure 12), the wavelength associated with the minimum value of the reflectance of s-polarized light adjacent to the target wavelength λ0 on the shorter wavelength side approaches the target wavelength λ0. Therefore, from the viewpoint of placing importance on the reflectance at the target wavelength λ0, the total number of pairs x of the adjustment structure 12 e is preferably 38 or less, more preferably 28 or less.

[0052] The electric field intensity distribution of s-polarized light when a laser LA with a target wavelength λ0=1064 nm is incident at an incident angle θ0=45° on the optical multilayer films of Comparative Examples 2-1 to 2-2 and the optical multilayer films 4 of Examples 2-1 to 2-4 is shown in Figures 32 to 37, respectively. In Comparative Example 2-1, the electric field strength of s-polarized light has maximum values ​​at odd-numbered interfaces, and the maximum value of the electric field strength of s-polarized light at all interfaces from 1 to 20 is 0.602 at the 19th interface. In Comparative Example 2-2, the maximum values ​​of the electric field strength of s-polarized light are located at the odd-numbered interfaces up to the 19th layer, but at the 21st and subsequent interfaces, the maximum values ​​of the electric field strength of s-polarized light are shifted toward the low-refractive-index layer from those interfaces. The maximum value of the electric field strength of s-polarized light at all interfaces is 0.434 at the 25th interface. In Comparative Example 2, the reflectance of s-polarized light at the target wavelength λ0=1064 nm and the incident angle θ0=45° is 99.5% or more, but the maximum value of the electric field strength of s-polarized light at all interfaces of the optical multilayer film 4 exceeds 0.4.

[0053] In Example 2-1, at the 21st and higher interfaces, the maximum value of the electric field strength of s-polarized light is shifted toward the low refractive index layer from that interface. The electric field strength of s-polarized light at the interfaces up to the 20th layer (primary reflection structure 10) is larger than that of the surrounding area because the maximum value of the electric field strength distribution of s-polarized light is located there, but this is sufficiently suppressed by the placement of the 21st and higher layers (adjustment structure 12) on the air side. The maximum value of the electric field strength of s-polarized light at all interfaces is 0.252 at the 33rd interface. In Example 2-2, the maximum value of the electric field strength of s-polarized light at the 21st and subsequent interfaces is shifted toward the low refractive index layer from the interface. The maximum value of the electric field strength of s-polarized light at all interfaces is 0.176 at the 45th interface. In Example 2-3, the maximum value of the electric field strength of s-polarized light at the 21st and subsequent interfaces is shifted toward the low refractive index layer from the interface. The maximum value of the electric field strength of s-polarized light at all interfaces is 0.132 at the 75th interface. In Example 2-4, the maximum value of the electric field strength of s-polarized light at the 21st and subsequent interfaces is shifted toward the low refractive index layer from the interface. The maximum value of the electric field strength of s-polarized light at all interfaces is 0.111 at the 93rd interface. In Example 2, the reflectance of s-polarized light at the target wavelength λ0=1064 nm and the incident angle θ0=45° is 99.5% or more, and the maximum value of the electric field strength of s-polarized light at all interfaces of the optical multilayer film 4 is 0.4 or less.

[0054] Furthermore, as shown in Table 8 below, when the manufacturing errors in Comparative Example 2 and Example 2 are simulated as described above, the expected values ​​of the maximum electric field strength at all interfaces are 0.602, 0.434, 0.251, 0.177, 0.135, and 0.118 for Comparative Examples 2-1 to 2-2 and Examples 2-1 to 2-4, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 99.72, 99.93, 99.97, 99.98, 99.99, and 99.99, respectively.

[0055] [Table 8]

[0056] In Comparative Example 2 and Example 2, the expected value of the reflectance at the target wavelength λ0 of s-polarized light is the same as the reflectance at the target wavelength λ0 of s-polarized light. In addition, in all of Examples 2-1 to 2-4, the difference between the expected value of the maximum electric field strength at the interface for s-polarized light and the maximum electric field strength at the interface for s-polarized light is small. In the case of oblique incidence of s-polarized light, there is a margin in the allowable film thickness deviation compared to normal incidence. In addition, in Examples 2-2 to 2-4 of Example 2, (total number of pairs x e = 13-38), the maximum and expected values ​​of the electric field strength at the interface for s-polarized light are low and stable. e In the range of θ = 13 or more, when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field intensity at the interface for a laser beam LA of target wavelength λ0 incident at an incident angle θ0 is 0.280 or less. In this case, the expected value of reflectivity is 99.5% or more.

[0057] [532nm normal incidence pair total number x e Changes - Example 3, Comparative Example 3 As comparative examples 3-1 and 3-2, as shown in Figures 38 and 39 and Table 9 below, the same as comparative examples 1-1 and 1-2 were created, respectively, except that the target wavelength λ0 of the laser LA was changed to 1064 nm with 532 nm in mind. As shown in Figures 40 and 41 and Table 10 below, Examples 3-1 and 3-2 were fabricated in the same order as Examples 1-1 and 1-2, except that the target wavelength λ0 of the laser LA was changed to 1064 nm with 532 nm in mind. As Examples 3-3 to 3-4, as shown in Figures 42 and 43 and Table 11 below, the same ones as Examples 1-3 to 1-4 were created in order, except that the target wavelength λ0 of the laser LA was changed to 1064 nm with 532 nm in mind. At a wavelength of 532 nm, the refractive index of the quartz glass substrate is 1.468, and the refractive index of the SiO2 layer is n L is 1.478, and the refractive index of the HfO2 layer, n H is 1.990.

[0058] [Table 9]

[0059] [Table 10]

[0060] [Table 11]

[0061] Figures 44 to 49 show the spectral reflectance distributions in the wavelength range (400 to 700 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 532 nm is incident on the optical multilayer films of Comparative Examples 3-1 to 3-2 and the optical multilayer films 4 of Examples 3-1 to 3-4 at an incident angle θ0 = 0°, respectively. In both Comparative Example 3 and Example 3, the reflectance at the target wavelength λ0 is close to 100%, and both Comparative Example 3 and Example 3 sufficiently reflect the laser LA of the target wavelength λ0. Furthermore, in the order of Comparative Examples 3-1 to 3-2 and Examples 3-1 to 3-4 (in the order of increasing number of layers of the adjustment structure 12), the wavelengths associated with the minimum values ​​of the reflectance adjacent to the target wavelength λ0 on the short wavelength side become closer to the target wavelength λ0. Therefore, from the viewpoint of placing importance relatively on the reflectance at the target wavelength λ0, the total number of pairs x of the adjustment structure 12 e is preferably 38 or less, more preferably 28 or less.

[0062] Figures 50 to 55 show the electric field intensity distributions when a laser LA with a target wavelength λ0 = 532 nm is incident at an incident angle θ0 = 0° on the optical multilayer films of Comparative Examples 3-1 to 3-2 and the optical multilayer films 4 of Examples 3-1 to 3-4, respectively. In Comparative Example 3-1, the electric field strength has its maximum value at the odd-numbered interfaces, and the maximum value of the electric field strength at all the 1st to 20th interfaces is 1.006 at the 19th interface. In Comparative Example 3-2, the electric field strength has maximum values ​​at the odd-numbered interfaces up to the 19th layer, but at the 21st and subsequent interfaces, the electric field strength maximum values ​​are shifted toward the low refractive index layer side from those interfaces. The maximum electric field strength value at all interfaces is 0.692 at the 25th interface. In Comparative Example 3, the reflectance at the target wavelength λ0=532 nm and the incident angle θ0=0° is 99.5% or more, but the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 exceeds 0.4.

[0063] In Example 3-1, at the 21st and higher interfaces, the maximum value of the electric field strength is shifted toward the low refractive index layer side from that interface. The electric field strength at the interfaces up to the 20th layer (main reflection structure 10) is larger than the surrounding area because the maximum value of the electric field strength distribution is located there, but this is sufficiently suppressed by the placement of the 21st and higher layers (adjustment structure 12) on the air side. The maximum value of the electric field strength at all interfaces is 0.344 at the 33rd interface. In Example 3-2, the maximum value of the electric field strength is shifted toward the low refractive index layer from the 21st interface and above. The maximum value of the electric field strength at all interfaces is 0.198 at the 45th interface. In Example 3-3, the maximum value of the electric field strength is shifted toward the low refractive index layer at the 21st and subsequent interfaces. The maximum value of the electric field strength at all interfaces is 0.114 at the 65th, 67th, 69th, 71st, 73rd, and 75th interfaces. In Example 3-4, the maximum value of the electric field strength is shifted toward the low refractive index layer at the 21st and subsequent interfaces. The maximum value of the electric field strength at all interfaces is 0.094 at the 89th interface. In Example 3, the reflectance at the target wavelength λ0=532 nm and the incident angle θ0=0° is 99.5% or more, and the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 is 0.4 or less.

[0064] Furthermore, as shown in Table 12 below, when the manufacturing errors in Comparative Example 3 and Example 3 are simulated as described above, the expected values ​​of the maximum electric field strength at all interfaces are 1.006, 0.692, 0.351, 0.220, 0.164, and 0.228 for Comparative Examples 3-1 to 3-2 and Examples 3-1 to 3-4, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 99.19, 99.75, 99.88, 99.93, 99.95, and 99.92, respectively.

[0065] [Table 12]

[0066] In Comparative Example 3 and Example 3, the expected value of the reflectance at the target wavelength λ0 is the same as the reflectance at the target wavelength λ0. Furthermore, among Example 3, in Examples 3-1 to 3-3, the difference between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface is small. Furthermore, among Examples 3-1 to 3-3, Examples 3-2 and 3-3 (total number of pairs x e =13,28), the maximum and expected values ​​of the electric field strength at the interface are low and stable. e In the range of = 13 to 28, when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field intensity at the interface is 0.280 or less for a laser LA of a target wavelength λ0 incident at an incident angle θ0. In this case, the expected value of the reflectance is 99.5% or more. e =38), when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field strength at the interface is 0.280 or less, and the expected value of the reflectance is 99.5% or more.

[0067] [1064nm normal incidence · total number of pairs x e Changes and material changes - Example 4, Comparative Example 4 As comparative examples 4-1 and 4-2, as shown in FIGS. 56 and 57 and Table 13 below, the high refractive index material was replaced with Ta2O5 instead of HfO2, and the low refractive index material was replaced with Ta2O5 having a refractive index of nL The same materials as Comparative Examples 1-1 and 1-2 were prepared in order, except that the refractive index n of Ta2O5 was different from that of SiO2. H is 2.086, and the refractive index of SiO2, n L The refractive index after film formation can vary depending on the film formation conditions (such as whether or not ion assistance is used during deposition), even when the same material is used. As shown in FIGS. 58 to 61 and the following Tables 14 to 15, Examples 4-1 to 4-4 were fabricated in the same order as Examples 1-1 to 1-4, except that the materials and refractive indexes were changed as in Comparative Example 4.

[0068] [Table 13]

[0069] [Table 14]

[0070] [Table 15]

[0071] Figures 62 to 67 show the spectral reflectance distributions in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident at an incident angle θ0 = 0° on the optical multilayer films of Comparative Examples 4-1 to 4-2 and the optical multilayer films 4 of Examples 4-1 to 4-4, respectively. In both Comparative Example 4 and Example 4, the reflectance at the target wavelength λ0 is close to 100%, and both Comparative Example 4 and Example 4 sufficiently reflect the laser LA of the target wavelength λ0. Furthermore, in the order of Comparative Examples 4-1 to 4-2 and Examples 4-1 to 4-4 (in the order of increasing number of layers of the adjustment structure 12), the wavelengths associated with the minimum values ​​of the reflectance adjacent to the target wavelength λ0 on the short wavelength side are closer to the target wavelength λ0. Therefore, from the viewpoint of placing importance relatively on the reflectance at the target wavelength λ0, the total number of pairs x of the adjustment structure 12 is eis preferably 38 or less, more preferably 28 or less.

[0072] Figures 68 to 73 show the electric field intensity distributions when a laser LA with a target wavelength λ0 = 1064 nm is incident at an incident angle θ0 = 0° on the optical multilayer films of Comparative Examples 4-1 to 4-2 and the optical multilayer films 4 of Examples 4-1 to 4-4, respectively. In Comparative Example 4-1, the electric field strength has its maximum value at the odd-numbered interfaces, and the maximum value of the electric field strength at all the 1st to 20th interfaces is 0.918 at the 19th interface. In Comparative Example 4-2, the electric field strength has maximum values ​​at the odd-numbered interfaces up to the 19th layer, but at the 21st and subsequent interfaces, the electric field strength maximum values ​​are shifted toward the low refractive index layer side from those interfaces. The maximum electric field strength value at all interfaces is 0.661 at the 25th interface. In Comparative Example 4, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, but the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 exceeds 0.4.

[0073] In Example 4-1, at the 21st and higher interfaces, the maximum value of the electric field strength is shifted toward the low refractive index layer side from that interface. The electric field strength at the interfaces up to the 20th layer (main reflection structure 10) is larger than the surrounding area because the maximum value of the electric field strength distribution is located there, but this is sufficiently suppressed by the placement of the 21st and higher layers (adjustment structure 12) on the air side. The maximum value of the electric field strength at all interfaces is 0.383 at the 33rd interface. In Example 4-2, the maximum value of the electric field strength is shifted toward the low refractive index layer from the 21st interface and above. The maximum value of the electric field strength at all interfaces is 0.267 at the 45th interface. In Example 4-3, the maximum value of the electric field strength is shifted toward the low refractive index layer at the 21st and subsequent interfaces. The maximum value of the electric field strength at all interfaces is 0.200 at the 75th interface. In Example 4-4, the maximum value of the electric field strength is shifted toward the low refractive index layer at the 21st and higher interfaces. The maximum value of the electric field strength at all interfaces is 0.168 at the 93rd interface. In Example 4, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, and the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 is 0.4 or less.

[0074] Furthermore, as shown in Table 16 below, when the manufacturing errors in Comparative Example 4 and Example 4 are simulated as described above, the expected values ​​of the maximum electric field strength at all interfaces are 0.918, 0.661, 0.383, 0.269, 0.205, and 0.180 for Comparative Examples 4-1 to 4-2 and Examples 4-1 to 4-4, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 99.70, 99.94, 99.98, 99.99, 100.00, and 100.00, respectively.

[0075] [Table 16]

[0076] In Comparative Example 4 and Example 4, the expected value of the reflectance at the target wavelength λ0 is the same as the reflectance at the target wavelength λ0. Furthermore, among Example 4, in Examples 4-1 to 4-3, the difference between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface is small. Furthermore, among Examples 4-1 to 4-3, at least Examples 4-2 and 4-3 (total number of pairs x e =13,28), the maximum and expected values ​​of the electric field strength at the interface are low and stable. e In the range of = 13 to 28, when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum value of the electric field intensity at the interface is 0.280 or less for a laser LA of the target wavelength λ0 incident at an incident angle θ0. In this case, the expected value of the reflectance is 99.5% or more. e=38), when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field strength at the interface is 0.280 or less, and the expected value of the reflectance is 99.5% or more.

[0077] [1064 nm - Adjustment structure film thickness change - Example 5, Comparative Example 5] As Comparative Example 5-1, as shown in FIG. 74 and Table 17 below, Example 1-1 (total number of pairs x) was used except that one pair (x=5) did not satisfy formula (17). e =7) was produced. In Table 17 etc. (tables for Example 5 and Comparative Example 5), the layers up to the 20th layer (the portion corresponding to the main reflective structure 10 in Example 1-1) are the same as those in Example 1-1, and therefore are omitted. Comparative Example 5-2 was produced in the same manner as Example 1-1, except that one pair (x=5) did not satisfy the formulas (15) and (16), as shown in FIG. 75 and Table 17 below. Comparative Example 5-3 was produced in the same manner as Example 1-1, except that one pair (x=5) did not satisfy formula (15), as shown in FIG. 76 and Table 18 below. Comparative Example 5-4 was produced in the same manner as Example 1-1, except that one pair (x=5) did not satisfy equations (15) and (16), as shown in FIG. 77 and Table 18 below. Comparative Example 5-5 was produced in the same manner as Example 1-1, except that one pair (x=5) did not satisfy the formulas (16) and (17), as shown in FIG. 78 and Table 19 below.

[0078] [Table 17]

[0079] [Table 18]

[0080] [Table 19]

[0081] As Example 5-1, as shown in FIG. 79 and Table 20 below, Example 1-1 (total number of pairs x) was used, except that the thicknesses of the low refractive index layer L and the high refractive index layer H were changed while satisfying the formulas (15) to (17) in one pair (x=5). e =7) was created. As Example 5-2, as shown in Figure 80 and Table 20 below, a structure similar to Example 1-1 was created, except that in two pairs (x = 4, 5), the film thicknesses of the low refractive index layer L and the high refractive index layer H were changed while satisfying equations (15) to (17). As Example 5-3, as shown in Figure 81 and Table 21 below, one pair (x = 5) was created that was similar to Example 1-1, except that the film thickness of the low refractive index layer L was changed while satisfying equations (15) to (17). As Example 5-4, as shown in Figure 82 and Table 21 below, one pair (x = 5) was created that was similar to Example 1-1, except that the film thickness of the high refractive index layer H was changed while satisfying equations (15) to (17). As Example 5-5, as shown in FIG. 83 and Table 22 below, Example 1-2 (total number of pairs x) was repeated except that the film thicknesses of the low refractive index layer L and the high refractive index layer H were changed while satisfying the formulas (15) to (17) in two pairs (x=4, 5). e =13) was created. As Example 5-6, as shown in FIG. 84 and Table 22 below, the same as Example 2-2 (total number of pairs x) was used except that the film thicknesses of the low refractive index layer L and the high refractive index layer H were changed while satisfying the formulas (15) to (17) in three pairs (x=3, 7, 11). e = 13, incident angle θ = 45°).

[0082] [Table 20]

[0083] [Table 21]

[0084] [Table 22]

[0085] Figures 85 to 94 show the spectral reflectance distributions in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident on the optical multilayer films of Comparative Examples 5-1 to 5-5 and the optical multilayer films 4 of Examples 5-1 to 5-5 at an incident angle θ0 = 0°, respectively. Furthermore, Figure 95 shows the spectral reflectance distribution of s-polarized light in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident on the optical multilayer film 4 of Example 5-6 at an incident angle θ0 = 45°. In both Comparative Example 5 and Example 5, the reflectance at the target wavelength λ0 is close to 100%, and both Comparative Example 5 and Example 5 sufficiently reflect the laser LA of the target wavelength λ0.

[0086] Figures 96 to 105 show the electric field intensity distributions when a laser LA with a target wavelength λ0 = 1064 nm is incident at an incident angle θ0 = 0° on the optical multilayer films of Comparative Examples 5-1 to 5-5 and the optical multilayer films 4 of Examples 5-1 to 5-5, respectively. FIG. 106 shows the electric field intensity distribution of s-polarized light when a laser beam LA having a target wavelength λ0=1064 nm is incident on the optical multilayer film 4 of Example 5-6 at an incident angle θ0=45°. In Comparative Example 5-1, the maximum value of the electric field strength at all interfaces is 0.578 at the 27th interface. In Comparative Example 5-2, the maximum value of the electric field strength at all interfaces is 0.454 at the 27th interface. In Comparative Example 5-3, the maximum value of the electric field strength at all interfaces is 0.452 at the 33rd interface. In Comparative Example 5-4, the maximum value of the electric field strength at all interfaces is 0.474 at the 29th interface. In Comparative Example 5-5, the maximum value of the electric field strength at all interfaces is 0.402 at the 29th interface. In Comparative Example 5, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, but the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 exceeds 0.4.

[0087] In Example 5-1, the maximum value of the electric field strength at all interfaces is 0.394 at the 27th interface. In Example 5-2, the maximum value of the electric field strength at all interfaces is 0.399 at the 25th interface. In Example 5-3, the maximum value of the electric field strength at all interfaces is 0.397 at the 33rd interface. In Example 5-4, the maximum value of the electric field strength at all interfaces is 0.371 at the 29th interface. In Example 5-5, the maximum value of the electric field strength at all interfaces is 0.204 at the 31st interface. In Example 5-6, the maximum value of the electric field strength of s-polarized light at all interfaces is 0.147 at the 45th interface. In all of Examples 5-1 to 5-5, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° was 99.5% or more, and the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 was 0.4 or less. In Example 5-6, the reflectance of s-polarized light at a target wavelength λ0=1064 nm and an incident angle θ0=45° is 99.5% or more, and the maximum value of the electric field strength of s-polarized light at all interfaces of the optical multilayer film 4 is 0.4 or less. According to the fifth embodiment, the optical thickness D L (m),D H (m) is the ideal value (reference value) within the range that satisfies equations (15) to (17). L (x),f H It can be seen that even if the value deviates from (x), the electric field intensity at each interface is suppressed while suppressing the decrease in reflectance.

[0088] Furthermore, as shown in Table 23 below, when the manufacturing errors in Comparative Example 5 and Example 5 are simulated as described above, the expected values ​​of the maximum electric field strength at all interfaces are 0.580, 0.455, 0.457, 0.474, 0.405, 0.395, 0.414, 0.407, 0.374, 0.246, and 0.154 for Comparative Examples 5-1 to 5-5 and Examples 5-1 to 5-6, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 99.76, 99.81, 99.87, 99.86, 99.83, 99.83, 99.82, 99.87, 99.84, 99.89, and 99.98, respectively.

[0089] [Table 23]

[0090] In Comparative Example 5 and Example 5, the expected values ​​of the reflectance at the target wavelength λ0 are similar to the reflectance at the target wavelength λ0. Furthermore, in Comparative Example 5 and Example 5, the difference between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface is small. Furthermore, in Examples 5-5 and 5-6, when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field strength at the interface is 0.280 or less, and the expected value of the reflectance is 99.5% or more.

[0091] [Changes other than the 1064 nm normal incidence / adjustment structure - Example 6, Comparative Example 6] As Comparative Example 6-1, as shown in FIG. 107 and Table 24 below, a structure similar to Example 1-1 was produced except that it did not have the main reflection structure 10. That is, Comparative Example 6-1 was produced with a total number of pairs x e 7 and an optical multilayer film including only the adjustment structure 12 and the protective film, As Example 6-1, as shown in FIG. 108 and Table 24 below, a sample similar to Example 1-1 was prepared except that it did not have a protective film (35th layer). Example 6-2 was produced in the same manner as Example 1-1, except that the first layer of the primary reflection structure 10 was omitted and the layer closest to the substrate was made into a high refractive index layer H, for a total of 15 layers, as shown in Figure 109 and Table 25 below. The number of layers in the optical multilayer film 4 of Example 6-2 was 29. As Example 6-3, a product similar to Example 6-2 was created, except that the optical film thickness for all layers of the main reflection structure 10 was multiplied by 1.02 (see the upper limit of the range in equations (8) and (9)), as shown in Figure 110 and Table 25 below. As Example 6-4, a product similar to Example 6-2 was created, except that the optical film thickness for all layers of the main reflection structure 10 was 0.95 times (see the lower limit of the range of equations (8) and (9)), as shown in Figure 111 and Table 26 below. As Example 6-5, a product similar to Example 6-2 was created, except that the optical film thickness of some layers of the main reflection structure 10 was varied within the range of equations (8) and (9), as shown in Figure 112 and Table 26 below.

[0092] [Table 24]

[0093] [Table 25]

[0094] [Table 26]

[0095] Figures 113 to 118 show the spectral reflectance distributions in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident at an incident angle θ0 = 0° on the optical multilayer film of Comparative Example 6-1 and the optical multilayer films 4 of Examples 6-1 to 6-5, respectively. In Comparative Example 6-1, the reflectance at the target wavelength λ0 is 82.3%, and the laser beam LA of the target wavelength λ0 is not reflected sufficiently. In contrast to this, in all of the sixth embodiment, the reflectance at the target wavelength λ0 is close to 100%, and all of the sixth embodiment sufficiently reflects the laser LA of the target wavelength λ0.

[0096] The electric field intensity distributions when a laser LA with a target wavelength λ0=1064 nm is incident at an incident angle θ0=0° on the optical multilayer film of Comparative Example 6-1 and the optical multilayer films 4 of Examples 6-1 to 6-4 are shown in Figures 119 to 124, respectively. In Comparative Example 6-1, the maximum value of the electric field strength at all interfaces is 0.367 at the 11th and 13th interfaces. In Comparative Example 6-1, the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 at the target wavelength λ0=1064 nm and the incident angle θ0=0° does not exceed 0.4, but the reflectance is less than 99.5%.

[0097] In Example 6-1, the maximum value of the electric field strength at all interfaces is 0.343 at the 29th interface. In Example 6-2, the maximum value of the electric field strength at all interfaces is 0.343 at the 24th interface. In Example 6-3, the maximum value of the electric field strength at all interfaces is 0.332 at the 24th interface. In Example 6-4, the maximum value of the electric field strength at all interfaces is 0.369 at the 26th interface. In Example 6-5, the maximum value of the electric field strength at all interfaces is 0.340 at the 24th interface. In Example 6, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, and the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 is 0.4 or less. According to the sixth embodiment, the optical thickness D L (m),D H It can be seen that even if (m) deviates from QW within the range that satisfies the formulas (6) to (9), the electric field intensity at each interface is suppressed while suppressing the decrease in reflectivity.

[0098] Furthermore, as shown in Table 27 below, when the manufacturing errors in Comparative Example 6 and Example 6 are simulated as described above, the expected values ​​of the maximum electric field strength at all interfaces are 0.373, 0.351, 0.350, 0.340, 0.377, and 0.347 for Comparative Example 6-1 and Examples 6-1 to 6-5, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 78.53, 99.85, 99.61, 99.54, 99.54, and 99.50, respectively.

[0099] [Table 27]

[0100] In Comparative Example 6 and Example 6, the expected value of the reflectance at the target wavelength λ0 is the same as the reflectance at the target wavelength λ0. Furthermore, in Comparative Example 6 and Example 6, the difference between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface is small.

[0101] [1064 nm normal incidence - actual measurement - Example 7, Comparative Example 7] Comparative Example 7-1 was actually fabricated by sputtering, as shown in Figure 125 and Table 28 below, with the low refractive index layer L being an SiO2 layer and the high refractive index layer H being an HfO2 layer, with the number of layers in the portion corresponding to primary reflection structure 10 being 38. The substrate in Comparative Example 7-1 was disk-shaped, with a diameter of 30 mm and a thickness of 3 mm. In Comparative Example 7-2, as shown in FIG. 126 and Table 28 below, the number of layers in the portion corresponding to the main reflection structure 10 is 34 (c L +c H = 33), and the optical film thickness of each high refractive index layer H (HfO2 layer) is reduced (0.988 times), and the total number of pairs x eThe optical film thickness of each high refractive index layer H was set to 2 (1.273 or 1.213 times the reference value), while the optical film thickness of each low refractive index layer L (SiO2 layer) was set to 0.661 or 0.650 times the reference value), and then the substrate in Comparative Example 7-2 was actually fabricated by sputtering. The substrate in Comparative Example 7-2 was the same as that in Comparative Example 7-1. In Example 7-1, as shown in FIG. 127 and Table 29 below, the number of layers per main reflection structure 10 is 30 (c L +c H =29), and the optical film thicknesses of some of the high refractive index layers H (HfO2 layers) and some of the low refractive index layers L (SiO2 layers) were varied (within the range of 0.987 to 1.052 times), and the optical film thickness of each high refractive index layer H of the adjustment structure 12 was varied (within the range of 0.836 to 1.109 times) relative to a reference value, and the optical film thickness of each low refractive index layer L was varied (within the range of 0.971 to 1.027 times) relative to a reference value, and then the substrate in Example 7-1 was actually fabricated by a sputtering method. The substrate in Example 7-1 was the same as that in Comparative Example 7-1.

[0102] [Table 28]

[0103] [Table 29]

[0104] Figures 128 to 130 show the spectral reflectance distributions in the wavelength range (900 to 1300 nm) around the target wavelength λ0 when a laser LA with a target wavelength λ0 = 1064 nm is incident on the optical multilayer films of Comparative Examples 7-1 to 7-2 and the optical multilayer film 4 of Example 7-1 at an incident angle θ0 = 0°. In both Comparative Example 7 and Example 7, the reflectance at the target wavelength λ0 is close to 100%, and both Comparative Example 7 and Example 7-1 sufficiently reflect the laser LA of the target wavelength λ0.

[0105] Figures 131 to 133 show the electric field intensity distributions when a laser LA with a target wavelength λ0=1064 nm is incident on the optical multilayer films of Comparative Examples 7-1 and 7-2 and the optical multilayer film 4 of Example 7-1 at an incident angle θ0=0°, respectively. In Comparative Example 7-1, the maximum value of the electric field strength at all interfaces is 1.047 at the 37th interface. In Comparative Example 7-2, the maximum value of the electric field strength at all interfaces is 0.590 at the 33rd interface. In Comparative Example 7, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=45° was 99.5% or more, but the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 exceeded 0.4.

[0106] In Example 7-1, the maximum value of the electric field strength at all interfaces is 0.187 at the 33rd interface. In Example 7, the reflectance at the target wavelength λ0=1064 nm and the incident angle θ0=0° is 99.5% or more, and the maximum value of the electric field strength at all interfaces of the optical multilayer film 4 is 0.4 or less.

[0107] Table 30 below shows the results of actual measurements of the laser induced damage threshold (LIDT) for the optical multilayer coatings of Comparative Examples 7-1 and 7-2 and the optical multilayer coating 4 of Example 7-1. The laser irradiation conditions were a wavelength of 1064 nm, a pulse width of 10 ns, an irradiation size of 0.5 mm, and an incident angle of 0°. The damage evaluation method was to change the irradiation position on the sample and the irradiation energy for each pulse and determine the minimum energy at which damage occurred (1 on 1).

[0108] [Table 30]

[0109] The LIDT of Example 7-1 is 200 [joules per square centimeter; J / cm 2 ] or more, and the laser resistance of Example 7-1 is superior to the laser resistance of Comparative Examples 7-1 and 7-2. According to Example 7, f L (x),f H It can be seen that optical products actually manufactured based on (x) etc. also suppress the decrease in reflectivity while suppressing the electric field strength at each interface, thereby providing sufficient resistance to high-power laser LA.

[0110] Furthermore, as shown in Table 30, when the manufacturing errors in Comparative Example 7 and Example 7 are simulated as described above, the expected values ​​of the maximum electric field strength at all interfaces are 1.048, 0.591, and 0.219 for Comparative Examples 7-1 to 7-2 and Example 7-1, respectively. In this case, the expected values ​​[%] of the reflectance at the target wavelength λ0 are 99.94, 99.95, and 99.97, respectively.

[0111] In Comparative Example 7 and Example 7, the expected value of the reflectance at the target wavelength λ0 is the same as the reflectance at the target wavelength λ0. Furthermore, in Comparative Example 7 and Example 7, the difference between the expected value of the maximum value of the electric field strength at the interface and the maximum value of the electric field strength at the interface is small. Furthermore, in Example 7-1, when a manufacturing error of ±1% is taken into consideration, the expected value of the maximum electric field strength at the interface is 0.280 or less, and the expected value of the reflectance is 99.5% or more. [Explanation of symbols]

[0112] 1··Mirror, 2··Substrate, 4··Optical multilayer film, 10··Main reflection structure, 12··Adjustment structure, H··High refractive index layer, L··Low refractive index layer, Q··Substrate surface.

Claims

1. A substrate; an optical multilayer film formed directly or indirectly on the surface of the substrate; It is equipped with the optical multilayer film has a primary reflection structure and an adjustment structure, the primary reflection structure is an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, and is arranged closer to the substrate than the adjustment structure; The adjustment structure is an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, and the target wavelength is adjusted to λ ０ The pair number, which is the number of pairs of a low refractive index layer and a high refractive index layer adjacent thereto on the opposite side of the substrate, counted from the substrate side, is represented by x, and the total number of pairs, which is the total number of pairs, is represented by x ｅ and λ of the low refractive index layer and the high refractive index layer at x. ０ Each optical thickness in units of / 4 is Ｌ (x), D Ｈ (x), and the refractive indices of the low refractive index layer, the high refractive index layer, and the incident medium are n Ｌ , n Ｈ , n ０ The physical thicknesses of the low refractive index layer and the high refractive index layer at x are respectively d Ｌ (x), d Ｈ (x), and the reference values ​​when considering oblique incidence in the low refractive index layer L and the high refractive index layer H are k Ｌ , k Ｈ The incident angle of the laser LA is θ ０ Then, the following formulas (A-0) to (A-9) are all satisfied. [Equation 1] A mirror characterized by:

2. The main reflection structure has a number of low refractive index layers (however, when a low refractive index layer is disposed as the first layer counted from the substrate side, the first layer is not counted) of c Ｌ , the number of high refractive index layers H is c Ｈ Counting from the substrate 2 side, m (= 1, ..., c Ｌ +c Ｈ ) the λ of the low refractive index layer and the high refractive index layer in the ０ Each optical thickness in units of / 4 is Ｌ (m), D Ｈ (m), and the physical film thickness of the mth layer is d Ｌ (m), d in the case of the high refractive index layer H Ｈ (m), and the sums in each low refractive index layer and each high refractive index layer are respectively Σ Ｌ , Σ Ｈ Then, the following formulas (B-1) to (B-9) are all satisfied. [Equation 2] 2. The mirror according to claim 1.

3. The x is 13 or more.

3. The mirror according to claim 1 or claim 2.

4. The x is 28 or less.

4. The mirror according to claim 1, wherein the mirror is a mirror having a thickness of 100 nm or less.

5. A substrate; an optical multilayer film formed directly or indirectly on the surface of the substrate; It is equipped with the optical multilayer film is an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, Incident angle θ ０ The target wavelength λ ０ the maximum values ​​of the electric field strength at all layer interfaces of the optical multilayer film for the laser are all 0.4 or less, and the electric field strength is expressed as the square of the absolute value of the ratio of the electric field in the optical multilayer film to the electric field of the incident laser (|electric field in the optical multilayer film / electric field of the incident laser| 2 ); Incident angle θ ０ The target wavelength λ ０ The target wavelength λ for the laser ０ The reflectance of the optical multilayer film at A mirror characterized by:

6. A substrate; an optical multilayer film formed directly or indirectly on the surface of the substrate; It is equipped with the optical multilayer film is an alternating film in which low refractive index layers made of a low refractive index material and high refractive index layers made of a high refractive index material are alternately arranged, Incident angle θ when considering a manufacturing error of ±1% ０ The target wavelength λ ０ the expected maximum values ​​of the electric field strength at all layer interfaces of the optical multilayer film for the laser are all 0.28 or less, and the electric field strength is expressed as the square of the absolute value of the ratio of the electric field in the optical multilayer film to the electric field of the incident laser (|electric field in the optical multilayer film / electric field of the incident laser| 2 ); Incident angle θ when considering a manufacturing error of ±1% ０ The target wavelength λ ０ The target wavelength λ for the laser ０ The expected reflectance of the optical multilayer film is 99.5% or more. A mirror characterized by:

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