Reflective element and optical device

Abstract

The embodiment of the invention provides a reflecting element and optical equipment. The reflecting element is used for reflecting light of a preset wave band and comprises a reflecting substrate and a multi-layer film arranged on the surface of the reflecting substrate. The multilayer film includes a plurality of second film layers and a plurality of first film layers. The multiple second film layers and the multiple first film layers are alternately arranged in the thickness direction of the multilayer film, and the refractive index of the second film layers is smaller than that of the first film layers. The wavelength corresponding to the minimum value of the absorption coefficient of the first film layer is located in a preset wave band, and the absorption coefficient of the first film layer to light of the preset wave band is smaller than 0.0018. According to the reflecting element and the optical equipment provided by the embodiment of the invention, the reflectivity of the reflecting element can be improved by controlling the absorption coefficient of the first film layer and the wave band of light, so that the energy utilization rate of the optical equipment is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of optical technology, and in particular to a reflective element and an optical device. Background Art

[0002] With the continuous evolution of optical technology, the wavelength of incident light waves used by optical systems has been continuously reduced, especially in the field of high-resolution imaging, and can even reach the X-ray band. At present, in short-waveband application scenarios, optical devices reflect the light emitted by the light source through a reflector coated with a multilayer film. However, due to the low reflectivity of the reflector coated with a multilayer film, the energy utilization rate of the optical device is low. Therefore, how to improve the energy utilization rate of optical devices has become a problem that needs to be solved urgently. Summary of the invention

[0003] The embodiments of the present application provide a reflective element and an optical device, which can improve the reflectivity of the reflective element by limiting the wavelength band of light reflected by the reflective element and the absorption coefficient of the first film layer in the reflective element, thereby improving the energy utilization rate of the optical device.

[0004] In a first aspect, the present application provides a reflective element, which is used to reflect light in a preset wavelength band, and includes a reflective substrate and a multilayer film disposed on the surface of the reflective substrate. The multilayer film includes a multilayer second film layer and a multilayer first film layer. Along the thickness direction of the multilayer film, the multilayer second film layer and the multilayer first film layer are arranged alternately, and the refractive index of the second film layer is less than the refractive index of the first film layer. The wavelength corresponding to the minimum value of the absorption coefficient of the first film layer is within the preset wavelength band, and the absorption coefficient of the first film layer to the light in the preset wavelength band is less than 0.0018.

[0005] Since the refractive index of the first film layer is greater than that of the second film layer, the multilayer film formed by alternating first and second film layers with different refractive indices meets the Bragg condition, so that the multilayer film absorbs less light, thereby making the reflective element have a higher reflectivity, creating basic conditions for improving the reflectivity of the reflective element.

[0006] In addition, since the refractive index of the first film layer is greater than that of the second film layer, by matching the material of the first film layer with the wavelength of the reflected light, the absorption coefficient of the first film layer to light in a preset band is made less than 0.0018, and the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer is within the preset band, thereby reducing the absorption of light by the multilayer film.

[0007] Therefore, by limiting the absorption coefficient of the first film layer and the wavelength of light reflected by the reflective element, the absorption of light can be reduced, thereby increasing the reflectivity of the reflective element, and further increasing the energy utilization rate of the optical device. In addition, after the reflectivity of the reflective element is improved, the heat conversion caused by absorption can be reduced, thereby reducing the risk of damage to the reflective element due to heat accumulation.

[0008] In a possible implementation manner, the ratio of the thickness of the first film layer to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64. The period thickness is the sum of the thickness of each of the first film layers and the thickness of each of the second film layers.

[0009] In the reflective element provided by the embodiment of the present application, the ratio of the thickness of the first film layer to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64, which can not only reduce the influence of the ratio of the thickness of the first film layer to the period thickness on the limit value of the theoretical reflectivity of the reflective element so that the theoretical reflectivity of the reflective element is located near the limit value of the theoretical reflectivity, but also can improve the actual reflectivity of the reflective element as much as possible on the basis of improving the theoretical reflectivity of the reflective element, thereby narrowing the gap between the actual reflectivity of the reflective element and the theoretical reflectivity. In addition, it can also ensure that the actual reflectivity of the reflective element is high, thereby improving the energy utilization rate of the optical device.

[0010] In a possible implementation manner, the sum of all the numbers of the second film layers and all the numbers of the first film layers in the multi-layer film is greater than or equal to 120.

[0011] The total number of second film layers and first film layers in the reflective element provided in the embodiment of the present application is greater than or equal to 120, which can not only make the theoretical reflectivity of the reflective element approach the limit value of the theoretical reflectivity, but also shorten the gap between the actual reflectivity of the reflective element and the theoretical reflectivity as much as possible, thereby improving the energy utilization of the optical device.

[0012] In a possible implementation manner, the roughness of the surface of the reflective substrate connected to the multilayer film is less than or equal to 0.1 nm.

[0013] The roughness of the surface where the reflective substrate and the multilayer film are connected in the reflective element provided in the embodiment of the present application is less than or equal to 0.1 nm, which can reduce the absorption of light by the reflective substrate, thereby further improving the actual reflectivity of the reflective element, and further improving the energy utilization of the optical device.

[0014] In a possible implementation, the second film layer is formed by at least one of the following materials: ruthenium, rhodium, molybdenum, niobium, zirconium, gold, platinum, silver, yttrium or iridium.

[0015] In a possible implementation manner, the material of the first film layer is silicon or beryllium.

[0016] In a possible implementation manner, the surface layer of the multi-layer film is the second film layer.

[0017] The surface of the multilayer film in the reflective element provided in the embodiment of the present application is the second film layer, which can not only reduce the thickness of the multilayer film but also improve the reflective effect of the reflective element.

[0018] In a possible implementation manner, the reflective substrate is connected to one of the multiple first film layers.

[0019] In the reflective element provided in the embodiment of the present application, the reflective substrate is connected to one of the multi-layer first film layers, which can not only reduce the difficulty of connecting the reflective substrate and the multi-layer film, but also improve the connection strength between the reflective substrate and the multi-layer film.

[0020] In a possible implementation manner, the reflective element is a reflector.

[0021] The second aspect of the present application provides an optical device, comprising a light source and a reflective element as described in any one of the first aspects. The reflective element is used to reflect light emitted by the light source with a wavelength within a preset wavelength band.

[0022] In the reflective element of the optical device provided by the embodiment of the present application, the absorption coefficient of the first film layer to the light of the wavelength emitted by the light source in the preset wavelength band is less than 0.0018, so that the absorption of the light of the preset wavelength band by the multilayer film is reduced, thereby increasing the reflection of the light by the multilayer film, and then increasing the reflectivity of the reflective element. In addition, when the wavelength of the light emitted by the light source is the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer, the absorption of the light by the first film layer can be minimized, thereby further improving the reflection of the light by the multilayer film, which helps to make the reflectivity of the reflective element reach the maximum value. Therefore, after improving the reflectivity of the reflective element, the energy utilization rate of the optical device can be improved, and the risk of thermal damage caused by absorption of the reflective element in the optical device can be reduced.

[0023] In a possible implementation, a working angle of the reflective element is greater than 0° and less than or equal to 80°.

[0024] The working angle of the reflective element of the optical device provided in the embodiment of the present application is greater than 0° and less than or equal to 80°, which can ensure that the reflectivity of the reflective element is significantly improved by limiting the absorption coefficient of the first film layer and the wavelength band of light reflected by the reflective element.

[0025] In a possible implementation, the light source is an accelerator light source.

[0026] The light source of the optical device provided in the embodiment of the present application adopts an accelerator light source, which can not only emit light with a wavelength within a preset band to improve the reflectivity of the reflective element, but also adjust the wavelength of the light to remove the constraints of the light band on the applicability and resolution of the optical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of an optical device provided in an embodiment of the present application;

[0028] Figure 2 A schematic structural diagram of a first reflective element provided in an embodiment of the present application;

[0029] Figure 3 is a reflectivity spectrum diagram when the roughness of the reflective substrate in the reflector in the related art is 0.3 nm;

[0030] Figure 4 for Figure 2 A reflectivity spectrum of the reflective element of the illustrated embodiment when the roughness of the surface where the reflective substrate is connected to the multilayer film is 0.3 nm;

[0031] Figure 5 for Figure 2 A reflectivity spectrum of the reflective element of the illustrated embodiment when the roughness of the surface where the reflective substrate is connected to the multilayer film is 0.1 nm;

[0032] Figure 6 A schematic diagram of the structure of a free electron laser light source provided in an embodiment of the present application;

[0033] Figure 7 A graph showing the absorption coefficient of the first film layer made of silicon material in different wavebands;

[0034] Figure 8 A graph showing the absorption coefficient of the first film layer made of beryllium material at different wavelengths;

[0035] Fig. 9 This is a reflectivity spectrum diagram when the first film layer in the reflective element provided in an embodiment of the present application is beryllium.

[0036] Description of reference numerals:

[0037] 100. Optical equipment;

[0038] 200, light source;

[0039] 210. Free electron laser light source;

[0040] 211. Electron source;

[0041] 212. Electron accelerator;

[0042] 213. Undulator;

[0043] 300, reflective element;

[0044] 10. Reflective substrate;

[0045] 20. Multilayer film;

[0046] 21. The first film layer;

[0047] 22. The second film layer. DETAILED DESCRIPTION

[0048] At present, with the continuous evolution of optical technology, the wavelength band of the incident light wave used by the optical system is constantly decreasing, especially in the field of high-resolution imaging, and can even reach the X-ray band. In short-band application scenarios, the incident light wave needs to use a reflector coated with a multilayer film as an effective reflection medium to obtain a higher reflectivity and light energy utilization rate. In the related art, the optical device includes a light source and a reflector coated with a multilayer film. The light source is a plasma light source, and its luminous spectrum is in a specific band with the highest luminous energy. The reflector coated with a multilayer film operates in the band where the luminous energy of the light source is the strongest.

[0049] However, since the light source uses a plasma light source, the luminescence spectrum of the plasma light source reaches its strongest point in a specific band and the available light energy is the largest. It is necessary to regulate the periodic thickness of the multilayer film so that the multilayer film matches this band, which restricts the energy utilization of the optical device.

[0050] In addition, since the light source is a plasma light source, in order to achieve the maximum output light energy of the optical device, the wavelength band of the light emitted by the light source cannot be adjusted, which also restricts the applicability and resolution of the optical device.

[0051] In addition, due to the low actual reflectivity of the multi-layer coated mirror, the total system efficiency of multiple mirrors in the optical device will be severely limited, so that a large amount of light energy is absorbed and the risk of thermal damage to the mirror is increased.

[0052] In order to solve the above problems, in the related art, the reflectivity of the reflector is usually improved by changing the structure of the multilayer film, thereby improving the energy utilization of the optical device and reducing the risk of thermal damage to the reflector due to absorption.

[0053] The following describes several methods of improving the reflectivity of a reflector coated with a multilayer film in the related art:

[0054] The first method of improving the reflectivity of a mirror coated with a multilayer film is to improve the reflectivity of the multilayer film by using a multilayer film combination with a variable period thickness ratio, thereby improving the actual reflectivity of the mirror, so that the actual reflectivity of the mirror is about 67.5%.

[0055] The second way to improve the reflectivity of a multi-layered mirror is to optimize the quality by adding an intermediate layer such as boron carbide or niobium between the multi-layers to increase the limit of the actual reflectivity of the mirror, so that the maximum actual reflectivity of the mirror is about 71%.

[0056] The third way to improve the reflectivity of the multi-layered mirror is to introduce a protective layer into the multi-layer to optimize the actual reflectivity of the mirror, so that the actual reflectivity of the mirror can reach 65%.

[0057] In summary, for a reflector coated with a multilayer film, although the actual reflectivity of the reflector can be optimized by interlayer insertion, protective layer or variable period thickness ratio, the film structure of the multilayer film will be complicated, thereby increasing the difficulty of manufacturing the multilayer film. In addition, although the reflectivity of the reflector can be improved by changing the structure of the multilayer film, the reflector is matched with the plasma light source, and the period thickness of the multilayer film needs to be adjusted to match the specific wavelength of the plasma light source, which also leads to the theoretical reflectivity limit of the reflector being about 75% and the actual reflectivity limit being about 70%, which restricts the energy utilization of the optical device.

[0058] In view of this, an embodiment of the present application provides a reflective element 300 and an optical device 100, which reduces the absorption of light by the multilayer film 20 by limiting the wavelength band of the light source 200 reflected by the reflective element 300 and the absorption coefficient of the first film layer 21 in the multilayer film 20 of the reflective element 300, thereby improving the theoretical reflectivity and / or actual reflectivity of the reflective element 300, thereby improving the energy utilization of the optical device 100 and reducing the risk of thermal damage to the reflective element 300 due to absorption.

[0059] The reflective element 300 and the optical device 100 provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0060] Figure 1 This is a schematic diagram of the structure of an optical device provided in an embodiment of the present application. Figure 1 As shown, the optical device 100 provided in the embodiment of the present application includes a light source 200 and a reflective element 300. The light source 200 is used to emit light with a wavelength within a preset wavelength band, and the reflective element 300 reflects light with a wavelength within the preset wavelength band.

[0061] It should be understood that the optical device 100 may also include other components, such as a controller, a display screen, a plane mirror, a spherical mirror, an aspherical mirror or a cylindrical mirror.

[0062] The optical device 100 provided in the embodiment of the present application may include but is not limited to an imaging device, an optical scanner, a lighting device, a display device, etc.

[0063] The reflective element 300 provided in the embodiment of the present application may include but is not limited to a reflector, a lens with a reflective function, etc. In the embodiment of the present application, the reflective element 300 is described as an example.

[0064] Figure 2 This is a schematic diagram of the structure of the first reflective element provided in the embodiment of the present application. Figure 2 As shown, the reflective element 300 provided in the embodiment of the present application includes a reflective substrate 10 and a multilayer film 20 disposed on the surface of the reflective substrate 10. The multilayer film 20 includes a multilayer second film layer 22 and a multilayer first film layer 21. Figure 2 In the X direction), the multi-layer second film layer 22 and the multi-layer first film layer 21 are arranged alternately, and the refractive index of the first film layer 21 is greater than the refractive index of the second film layer 22. The wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21 is within the preset wavelength band, and the absorption coefficient of the first film layer 21 for light in the preset wavelength band is less than 0.00018.

[0065] In the embodiment of the present application, the reflective substrate 10 is used to carry the multilayer film 20 and to fix the reflective element 300. Of course, in the process of the reflective element 300 reflecting light, the light of the preset wavelength band first contacts the multilayer film 20, and the reflective substrate 10 can also be used to reflect the light passing through the multilayer film 20 to improve the reflectivity of the reflective element 300.

[0066] Among them, the absorption coefficient is a property of the medium itself, which refers to the measure of the medium's ability to absorb light. In addition, the medium absorbs light of different wavelengths differently, so the medium has different absorption coefficients for light of different wavelengths. In addition, different materials absorb the same wavelength differently, so the absorption coefficients of media of different materials for the same wavelength are also different.

[0067] In the embodiment of the present application, the refractive index of the second film layer 22 is lower than the refractive index of the first film layer 21, which is explained numerically. However, if described from the perspective of materials, the first film layer 21 is composed of a low refractive index material, and the second film layer 22 is composed of a high refractive index material. Among them, the low refractive index of the low refractive index material is not low in value, but is closer to 1 than the high refractive index material. Similarly, the high refractive index of the high refractive index material is not high in value, but is more deviated from 1 than the low refractive index material.

[0068] Since the first film layer 21 is made of a low refractive index material and the second film layer 22 is made of a high refractive index material, the first film layer 21 and the second film layer 22 with different refractive indices are alternately arranged along the thickness direction of the multilayer film 20, so that the multilayer film 20 satisfies the Bragg condition, thereby reducing the absorption of light by the multilayer film 20, which can create basic conditions for improving the reflectivity of the reflective element 300.

[0069] Since the absorption coefficient of the first film layer 21 is different at different wavelengths, in the embodiment of the present application, by limiting the wavelength of the light emitted by the light source 200 within the preset wavelength band, it can be ensured that the absorption coefficient of the first film layer 21 for the light in the preset wavelength band is less than 0.0018, so that the absorption of the light in the preset wavelength band by the multilayer film 20 is reduced. Therefore, by matching the wavelength band of the light reflected by the reflective element 300 with the material of the first film layer 21, the absorption coefficient of the first film layer 21 can be made less than 0.0018, so that the absorption of light by the multilayer film 20 can be reduced, and then the actual reflectivity and theoretical reflectivity of the reflective element 300 can be improved, that is, the reflectivity of the reflective element 300 can be improved. Since the reflectivity of the reflective element 300 is improved, the energy utilization rate of the optical device 100 can also be improved, and in addition, the risk of damage to the reflective element 300 due to heat absorption can also be reduced.

[0070] In the embodiment of the present application, there is no particular limitation on how the multilayer film 20 is disposed on the surface of the reflective substrate 10. In one embodiment, the multilayer film 20 can be plated on the surface of the reflective substrate 10 by coating.

[0071] Figure 3 is a reflectivity spectrum diagram when the roughness of the reflective substrate in the reflector in the related art is 0.3 nm, Figure 4 for Figure 2 The reflectivity spectrum of the reflective element of the embodiment shown is when the roughness of the surface where the reflective substrate and the multilayer film are connected is 0.3nm. Figure 3 and Figure 4 The M in the equation is the theoretical reflectivity, and the N in the equation is the actual reflectivity. Figure 3 and Figure 4 It can be seen that, under the condition that the surface roughness of the reflective substrate 10 and the multilayer film 20 is the same, the absorption coefficient of the first film layer 21 to the light in the preset wavelength band is limited to less than 0.0018, so that the actual reflectivity changes from 65% to 70%, and the theoretical reflectivity changes from 75% to 78.3%. Therefore, limiting the absorption coefficient of the first film layer 21 to the light in the preset wavelength band to less than 0.0018 can reduce the absorption of the light in the preset wavelength band, which will greatly improve the actual reflectivity and theoretical reflectivity of the reflective element 300.

[0072] In the embodiment of the present application, the ratio of the thickness of the first film layer 21 to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64, wherein the period thickness is the sum of the thickness of the first film layer 21 and the thickness of the second film layer 22 .

[0073] In the embodiment of the present application, there is no limitation on the specific ratio of the thickness of the first film layer 21 to the periodic thickness. For example, the specific ratio of the thickness of the first film layer 21 to the periodic thickness may include but is not limited to 0.58, 0.588, 0.590, 0.5963, 0.6, 0.6102, 0.619, 0.62, 0.625, 0.63, 0.633, 0.6392, 0.64, etc.

[0074] Of course, in addition to being greater than or equal to 0.57 and less than or equal to 0.64, the ratio of the thickness of the first film layer 21 to the period thickness may also be greater than 0.64 and less than 0.69 in one embodiment. Or in one embodiment, the ratio of the thickness of the first film layer 21 to the period thickness may also be greater than 0.54 and less than 0.57. Therefore, when the ratio of the thickness of the first film layer 21 to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64, the ratio of the thickness of the first film layer 21 to the period thickness will have a greater impact on the theoretical reflectivity of the reflective element 300, causing the theoretical reflectivity of the reflective element 300 to decrease by more than 0.2% compared to the peak value.

[0075] In summary, by controlling the ratio of the thickness of the first film layer 21 to the period thickness within the range of 0.57 to 0.64, not only can the decrease in the theoretical reflectivity of the reflective element 300 caused by the ratio of the thickness of the first film layer 21 to the period thickness be controlled to ensure that the theoretical reflectivity is near the limit value of the theoretical reflectivity, but also the actual reflectivity of the reflective element 300 can be increased as much as possible on the basis of increasing the theoretical reflectivity, thereby narrowing the gap between the theoretical reflectivity and the actual reflectivity. In addition, the actual reflectivity of the reflective element 300 can be ensured to be high, thereby improving the energy utilization of the optical device 100 and reducing the risk of damage to the reflective element 300 due to heat absorption.

[0076] In the embodiments of the present application, there is no specific limitation on how to determine the period thickness. In one embodiment, the formula for calculating the period thickness is d=nλ / (2sinθ). Wherein, λ is the wavelength of the light emitted by the light source 200, n is the diffraction order and n is a positive integer, and θ is the working angle of the reflective element 300 (the incident angle of the light emitted by the light source 200, such as Figure 2 Therefore, according to the wavelength and incident angle of the light emitted by the light source 200, the period thickness of the multilayer film 20 can be determined.

[0077] The value range of n can be determined according to actual needs and is not particularly limited here. For example, the value range of n is 1 to 2.

[0078] In the embodiment of the present application, the sum of all the layers of the second film layer 22 and all the layers of the first film layer 21 in the multilayer film 20 is greater than or equal to 120.

[0079] In the embodiment of the present application, there is no limitation on the specific value of the total number of layers of the second film layer 22 and the first film layer 21. The total number of layers of the second film layer 22 and the first film layer 21 may include but is not limited to 130, 135, 140, 150, 160, 170, 180, 190, 200, 210, 224, 240, etc.

[0080] It should be understood that, as the total number of the first film layer 21 and the second film layer 22 increases, the reflectivity of the reflective element 300 will be closer to the limit value of the reflectivity.

[0081] In summary, the total number of layers of the second film layer 22 and the first film layer 21 in the reflective element 300 provided in the embodiment of the present application is greater than or equal to 120, which can not only make the theoretical reflectivity of the reflective element 300 approach the limit value of the theoretical reflectivity, but also further improve and narrow the gap between the actual reflectivity of the reflective element 300 and the theoretical reflectivity, thereby improving the energy utilization of the optical device 100 and reducing the risk of damage to the reflective element 300 due to heat absorption.

[0082] In the embodiment of the present application, there is no limitation on the material of the reflective substrate 10. The material of the reflective substrate 10 may include but is not limited to optical glass such as silicon (Si), silicon carbide (SiC) or quartz.

[0083] In the embodiment of the present application, the roughness of the surface where the reflective substrate 10 is connected to the multilayer film 20 is less than or equal to 0.1 nm. Accordingly, in the reflective element 300 provided in the embodiment of the present application, the roughness of the surface where the reflective substrate 10 is connected to the multilayer film 20 is less than or equal to 0.1 nm, which can reduce the absorption of light by the reflective substrate 10, thereby further improving the actual reflectivity of the reflective element 300, and further improving the energy utilization of the optical device 100, and further reducing the risk of damage to the reflective element 300 caused by absorption.

[0084] It should be understood that the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected will not affect the theoretical reflectivity of the reflective element 300, but will only affect the actual reflectivity of the reflective element 300. This is because the theoretical reflectivity of the reflective element 300 is the reflectivity of "the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected = 0".

[0085] Figure 5 for Figure 2 The reflectivity spectrum of the reflective element of the illustrated embodiment is a graph when the roughness of the surface connecting the reflective substrate and the multilayer film is 0.1 nm.

[0086] Among them, Figure 5 In FIG. 2 , M is the theoretical reflectivity of the reflective element 300, and N is the actual reflectivity of the reflective element 200. Figure 4 It can be seen that when the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected is 0.3 nm, the theoretical reflectivity of the reflective element 300 is 78.5%. Figure 5 It can be seen that when the roughness of the surface connecting the reflective substrate 10 and the multilayer film 20 is 0.1 nm, the theoretical reflectivity of the reflective element 300 is 78.5%. It can be seen that the roughness of the surface connecting the reflective substrate 10 and the multilayer film 20 does not affect the theoretical reflectivity of the reflective element 300.

[0087] The smaller the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected, the smoother the surface where the reflective substrate 10 and the multilayer film 20 are connected, and the less the reflective substrate 10 absorbs light, so the actual reflectivity of the reflective element 300 is higher. Figure 4 It can be seen that when the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected is 0.3 nm, the actual reflectivity of the reflective element 300 is about 70%. Figure 5 It can be seen that when the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected is 0.1 nm, the actual reflectivity of the reflective element 300 is 73.3%. It can be seen that the smaller the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected, the closer the actual reflectivity of the reflective element 300 is to the limit value of the theoretical reflectivity.

[0088] In the embodiment of the present application, there is no limitation on the specific value of the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected, for example, it can be 0.1nm, 0.099nm, 0.09nm, 0.08nm, 0.07nm, 0.06nm, 0.05nm, 0.04nm, 0.01nm, etc.

[0089] In the embodiment of the present application, there is no specific limitation on the material of the second film layer 22, as long as the material of the second film layer 22 is a material with a high refractive index relative to the first film layer 21. For example, the material of the second film layer 22 provided in the embodiment of the present application may include, but is not limited to, ruthenium (Ru), rhodium (Rh), molybdenum (Mo), niobium (Nb), zirconium (Zr), gold (Au), silver (Ag), platinum (Pt), yttrium (Y) or iridium (Ir).

[0090] It should be noted that the second film layer 22 may be composed not only of metal materials but also of non-metal materials, or even of a compound of metal materials and non-metal materials.

[0091] It should also be noted that the second film layer 22 may be made of at least one material, for example, the second film layer 22 may be made of niobium, or may be made of an alloy.

[0092] In the embodiment of the present application, there is no limitation on the specific material of the first film layer 21, as long as the material of the first film layer 21 is a material with a lower refractive index than the second film layer 22. For example, the material of the first film layer 21 provided in the embodiment of the present application may include but is not limited to silicon (Si), beryllium (Be), etc.

[0093] In one embodiment, the surface layer of the multilayer film 20 is the second film layer 22. Of course, in addition to the second film layer 22, the surface layer of the multilayer film 20 may also be the first film layer 21.

[0094] Accordingly, no matter the surface layer of the multilayer film 20 of the reflective element 300 is the second film layer 22 or the first film layer 21, the reflective element 300 has a high reflectivity and can meet the use requirements. However, when the surface layer of the multilayer film 20 is the second film layer 22, not only can the thickness of the multilayer film 20 be reduced, but also the reflective effect of the reflective element 300 can be improved.

[0095] In one embodiment, continue to refer to Figure 2 As shown, the reflective substrate 10 is connected to one of the multi-layer first film layers 21. Of course, in addition to the first film layer 21, the film layer connected to the reflective substrate 10 in the multi-layer film 20 can also be connected to the second film layer 22 in the multi-layer film 20 in one embodiment.

[0096] Correspondingly, the reflective substrate 10 is connected to the first film layer 21 or the second film layer 22, and the reflective substrate 10 is connected to the multilayer film 20. However, in the embodiment of the present application, since the material of the first film layer 21 is silicon, and the reflective substrate 10 can be composed of a material containing silicon elements such as silicon (Si), silicon carbide (SiC) or optical glass, the first film layer 21 is connected to the reflective substrate 10 under the premise that the materials of the first film layer 21 and the reflective substrate 10 both contain silicon elements, which can not only reduce the difficulty of connecting the reflective substrate 10 to the multilayer film 20, but also improve the firmness of the connection between the reflective substrate 10 and the multilayer film 20.

[0097] In the embodiment of the present application, the working angle of the reflective element 300 is greater than 0° and less than or equal to 80°. Accordingly, the working angle of the reflective element 300 of the optical device 100 provided in the embodiment of the present application is greater than 0° and less than or equal to 80°, which can ensure that the reflectivity of the reflective element 300 is significantly improved by limiting the absorption coefficient of the first film layer 21 and the wavelength band of the light reflected by the reflective element 300.

[0098] In the embodiment of the present application, the working angle of the reflective element 300 refers to the angle between the incident principal light and the normal line of the reflective surface of the reflective element 300. In other words, it is the incident angle of the light emitted by the light source 200 to the reflective element 300, such as Figure 2 As shown in θ.

[0099] It should be understood that the size of the working angle of the reflective element 300 does not affect the theoretical reflectivity and actual reflectivity of the reflective element 300. However, when the working angle of the reflective element 300 exceeds 80°, the incident light directed to the reflective element 300 is grazing incidence. Due to the significant effect of grazing incidence, the effect of the solution of the embodiment of the present application is no longer obvious. Of course, when the angle of incidence exceeds 80°, the solution provided in the embodiment of the present application can also be used to improve the reflectivity of the reflective element 300, but due to some factors, the advantages of the solution provided in the embodiment of the present application are not significant. Among them, the reflectivity of the reflective element 300 at grazing incidence is not affected by the solution provided in the embodiment of the present application. In addition, grazing incidence refers to the propagation of light from an optically sparse medium to an optically dense medium, and the angle of incidence is close to 90°.

[0100] In the embodiment of the present application, the light source 200 is an accelerator light source, which can not only emit light of a preset wavelength band corresponding to the minimum value of the absorption coefficient of the first film layer 21, thereby improving the reflectivity of the reflective element 300, but also adjust the wavelength of the light emitted by the light source 200, thereby removing the constraints of the light band on the applicability and resolution of the optical device 100.

[0101] Since the light emitted by the accelerator light source is narrow-spectrum light, the wavelength of the light emitted by the accelerator light source can be a preset wavelength, so that the wavelength of the light emitted by the accelerator light source can be matched with the absorption coefficient of the first film layer 21. Therefore, compared with the light emitted by the plasma light source in the related art, which is wide-spectrum light and thus requires adjusting the period thickness of the multilayer film 20 to match the wavelength of the light, in the embodiment of the present application, it is not necessary to adjust the period thickness to match the wavelength of the light emitted by the accelerator light source, so that the wavelength of the light emitted by the accelerator light source does not limit the applicability and resolution of the optical device 100.

[0102] The accelerator light source provided in the embodiment of the present application may include but is not limited to a free electron laser light source 210, a synchrotron radiation light source, etc. In the embodiment of the present application, the free electron laser light source 210 is taken as the above light source 200 for example.

[0103] Figure 6 A schematic diagram of the structure of a free electron laser light source provided in an embodiment of the present application. Figure 6As shown, the free electron laser light source 210 includes an electron source 211, an electron accelerator 212 and an undulator 213. The electron source 211 is used to generate an electron beam. The electron accelerator 212 is arranged on the electron beam path behind the electron source 211 to accelerate the electron beam. The undulator 213 generates radiation pulses using the electron beam.

[0104] The wavelength of the light emitted by the free electron laser light source 210 can be controlled by the following formula:

[0105]

[0106] Wherein, λu is the undulator period, γ is the electron momentum (from the electron accelerator 212), K is the electron deflection factor, and λ is the wavelength of the light emitted by the free electron laser light source 210 and is within a preset wavelength band.

[0107] It should be noted that, according to usage requirements, by setting the values ​​of electron momentum and electron deflection factor, and combining that the wavelength of light emitted by the free electron laser light source 210 should be within the band corresponding to the minimum value of the absorption coefficient of the first film layer 21, the undulator period can be obtained, and then the free electron laser light source 210 can emit light of the corresponding wavelength.

[0108] The following is a description of why the solution provided in the embodiment of the present application can improve the theoretical reflectivity and actual reflectivity of the reflective element 300 in conjunction with specific embodiments.

[0109] Embodiment 1

[0110] In this embodiment, the material of the first film layer 21 is silicon (Si), and the material of the second film layer 22 is molybdenum (Mo).

[0111] Figure 7 This is a graph showing the absorption coefficient of the first film layer made of silicon material in different bands. Figure 7 As shown, the minimum value of the absorption coefficient of the first film layer 21 is 0.0017901, and the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21 is 12.73nm. Therefore, in this embodiment, the wavelength of 12.73nm is selected as the light emission wavelength of the light emitted by the light source 200, which can maximize the reduction of the absorption of light by the multilayer film 20, thereby improving the reflectivity of the reflective element 300.

[0112] In this embodiment, since a wavelength of 12.73 nm is selected as the light emission wavelength of the light emitted by the light source 200 , correspondingly, the period thickness is 6.46 nm.

[0113] In this embodiment, the ratio of the thickness of the first film layer 21 to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64.

[0114] In this embodiment, the total number of layers of the first film layer 21 and the second film layer 22 is greater than or equal to 200 layers.

[0115] In this embodiment, the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected is less than or equal to 0.1 nm.

[0116] In this embodiment, the light source 200 is a free electron laser light source 210. According to the adjustment formula of the light emission wavelength, when γ=1975 (the electron energy is 1 GeV), the electron deflection factor K=2.4, λu=2.56cm, the light emission wavelength λ=12.73nm, so that the wavelength of the light emitted by the free electron laser light source 210 matches the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21.

[0117] Combination Figure 4 and Figure 5 It can be seen that when the wavelength of light is 12.73nm, the absorption coefficient of the first film layer 21 can reach 0.0017901, so that the maximum theoretical reflectivity of the reflective element 300 can reach 78.5%, and limited by factors such as film scattering and roughness absorption, the actual reflectivity of the reflective element 300 can reach up to 73.3%.

[0118] Assuming that 10 reflective elements 300 are provided in the optical device 100, in the related art, the actual reflectivity of the reflective element 300 is between 65% and 70.2%, so that the total efficiency of the optical device 100 is 0.65. 10 = 1.346%, or up to 0.72 10 =2.907%. In this embodiment, since the actual reflectivity of the reflective element 300 can reach 73.3%, the total efficiency of the optical device 100 is 0.733 10 =4.478%, which is 3.32 or 1.54 times higher than the total efficiency of the optical device 100 in the related art.

[0119] In summary, by adjusting the absorption coefficient of the first film layer 21 of the reflective element 300 to match the wavelength of the light emitted by the light source 200, the absorption of light by the reflective element 300 can be reduced, thereby improving the actual reflectivity and theoretical reflectivity of the reflective element 300, for example, the actual reflectivity of a single reflective element 300 reaches 73.3% and the theoretical reflectivity reaches 78.5%. In addition, after the reflectivity of a single reflective element 300 is improved, the energy utilization rate (output power) of the optical device 100 can be improved, thereby improving the optical output power of the optical device 100. In other words, under the same output power, after the energy utilization rate of the optical device 100 is improved, the input power requirement of the optical device 100 can be greatly reduced. In addition, the improvement of the reflectivity of the reflective element 300 can reduce the heat conversion caused by absorption, and reduce the risk of thermal damage to the reflective element 300 due to heat accumulation.

[0120] Embodiment 2

[0121] In this embodiment, the material of the first film layer 21 is beryllium (Be), and the material of the second film layer 22 is molybdenum (Mo).

[0122] Figure 8 The absorption coefficient of the first film layer made of beryllium material at different wavelengths is shown in FIG. Figure 8 It can be seen that the minimum value of the absorption coefficient of the first film layer 21 is 0.001118, and the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21 is 11.43 nm. Therefore, in this embodiment, the wavelength of 11.43 nm is selected as the light emission wavelength of the light emitted by the light source 200, which can maximize the reduction of the absorption of light by the multilayer film 20, thereby improving the reflectivity of the reflective element 300.

[0123] In this embodiment, since a wavelength of 11.43 nm is selected as the light emission wavelength of the light emitted by the light source 200 , correspondingly, the period thickness may be 5.58 nm.

[0124] In this embodiment, the ratio of the thickness of the first film layer 21 to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64.

[0125] In this embodiment, the total number of layers of the first film layer 21 and the second film layer 22 is greater than or equal to 200 layers.

[0126] In this embodiment, the roughness of the surface where the reflective substrate 10 and the multilayer film 20 are connected is less than or equal to 0.1 nm.

[0127] In this embodiment, the light source 200 is a free electron laser light source 210. According to the adjustment formula of the light emission wavelength, when γ=1975 (the electron energy is 1 GeV), the electron deflection factor K=2.4, λu=2.45cm, the light emission wavelength λ1=11.42nm, so that the wavelength of the light emitted by the free electron laser light source 210 matches the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21.

[0128] Fig. 9 This is a reflectivity spectrum diagram when the first film layer in the reflective element provided in the embodiment of the present application is beryllium. Fig. 9 It can be seen that when the wavelength of light is 11.43nm, the absorption coefficient of the first film layer 21 can reach 0.001118, and the maximum theoretical reflectivity of the reflective element 300 can reach 77.4%. When limited by factors such as film scattering and roughness absorption, the actual reflectivity of the reflective element 300 can reach 71%.

[0129] In summary, by matching the material of the first film layer 21 with the wavelength of the light emitted by the light source 200, even if the absorption coefficient of the first film layer 21 to the light emitted by the light source 200 is less than 0.0018, the absorption of the light emitted by the light source 200 by the reflective element 300 is reduced, thereby improving the reflectivity of the light emitted by the light source 200 by the reflective element 300.

[0130] The following describes how to determine the preset wavelength band of the light reflected by the reflective element 300 according to the minimum value of the absorption coefficient of the first film layer 21 .

[0131] In the embodiment of the present application, since the absorption coefficient of the first film layer 21 for different wavelengths is different, the reflectivity of the reflective element 300 for different wavelengths is different. Among them, when the wavelength of the light reflected by the reflective element 300 is the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21, the reflectivity of the reflective element 300 reaches the maximum value. When the wavelength of the light reflected by the reflective element 300 is near the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21, although the reflectivity of the reflective element 300 is lower than the maximum value, it is still higher than the reflectivity of the emitting element 300 in the related art. Therefore, the preset band is determined by comparing the maximum value of the reflectivity of the reflective element 300 with the reflectivity of the reflective element 300 in the related art. In other words, the band corresponding to the reflectivity corresponding to the minimum value of the absorption coefficient of the first film layer 21 decreases by a predetermined amplitude, and the predetermined amplitude is equal to the reflectivity corresponding to the minimum value of the absorption coefficient of the first film layer 21 minus the reflectivity of the reflective element 300 in the related art.

[0132] In the embodiment of the present application, there is no limitation on the reflectivity of the reflective element 300 in the related art. In the embodiment of the present application, an actual reflectivity of 70% is taken as an example to illustrate how to determine the preset band.

[0133] In one embodiment, when the material of the first film layer 21 is silicon, the absorption coefficient of the first film layer 21 for different wavelengths is as follows: Figure 7 As shown, the reflectivity spectrum of the reflective element 300 is as shown in Figure 5 As shown, correspondingly, the minimum value of the absorption coefficient of the first film layer 21 is 0.0017901, and the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21 is 12.73nm. Since the maximum value of the reflectivity in the related art is 70%, the wavelength band corresponding to the wavelength near 12.73nm with an emissivity greater than 70% is approximately 12.57nm to 13.17nm, that is, the preset wavelength band is 12.57nm to 13.17nm. Figure 7 It can be seen that the absorption coefficient of the first film layer 21 corresponding to the preset wavelength band is 0.001802 (12.57 nm) to 0.001808 (13.17 nm), both of which meet the requirement of being less than 0.0018.

[0134] In one embodiment, when the material of the first film layer 21 is beryllium, the absorption coefficient of the first film layer 21 for different wavelengths is as follows: Figure 8 As shown, the reflectivity spectrum of the reflective element 300 is as shown in Fig. 9 As shown, correspondingly, the minimum value of the absorption coefficient of the first film layer 21 is 0.001118, and the wavelength corresponding to the minimum value of the absorption coefficient of the first film layer 21 is 11.43nm. Since the maximum value of the reflectivity in the related art is 70%, the wavelength band corresponding to the reflectivity greater than 70% near the wavelength of 11.43nm is approximately 11.167nm~11.5nm, that is, the preset wavelength band is 11.167nm~11.5nm. Figure 8 It can be seen that the absorption coefficient of the first film layer 21 corresponding to the preset wavelength band is 0.001301 (11.167 nm) to 0.0012 (11.5 nm), both of which meet the requirement of being less than 0.0018.

[0135] It should be noted that when the absorption coefficient of the same medium for the same wavelength is measured in different ways, the absorption coefficient obtained may be slightly different. In other words, the wavelength corresponding to the same absorption coefficient of the medium obtained by different measurement methods may be different.

[0136] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0137] In the embodiments of the present application, the devices or elements referred to or implied must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise precisely and specifically specified.

[0138] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the embodiments of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0139] The term "plurality" in this article refers to two or more than two. The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the previous and next associated objects are in an "or" relationship; in a formula, the character " / " indicates that the previous and next associated objects are in a "division" relationship.

[0140] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0141] It can be understood that in the embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

Claims

1. A reflective element, characterized in that: The reflective element is used to reflect light of a preset wavelength band, and the reflective element includes a reflective substrate and a multilayer film arranged on the surface of the reflective substrate; The multilayer film comprises a plurality of first film layers and a plurality of second film layers; Along the thickness direction of the multilayer film, the multilayer second film layers and the multilayer first film layers are arranged alternately, and the refractive index of the second film layers is smaller than the refractive index of the first film layers; The wavelength corresponding to the minimum value of the absorption coefficient of the first film layer is within the preset wavelength band, and the absorption coefficient of the first film layer to the light in the preset wavelength band is less than 0.0018.

2. The reflective element according to claim 1, characterized in that A ratio of the thickness of each of the first film layers to the period thickness is greater than or equal to 0.57 and less than or equal to 0.64; wherein the period thickness is the sum of the thickness of each of the first film layers and the thickness of each of the second film layers.

3. The reflective element according to claim 1 or 2, characterized in that: The sum of all the numbers of the second film layers and all the numbers of the first film layers in the multilayer film is greater than or equal to 120.

4. The reflective element according to any one of claims 1 to 3, characterized in that: The roughness of the surface of the reflective substrate connected to the multilayer film is less than or equal to 0.1 nm.

5. The reflective element according to any one of claims 1 to 4, characterized in that: The second film layer is made of at least one of the following materials: ruthenium, rhodium, molybdenum, niobium, zirconium, gold, platinum, silver, yttrium or iridium.

6. The reflective element according to any one of claims 1 to 5, characterized in that: The material of the first film layer is silicon or beryllium.

7. The reflective element according to any one of claims 1 to 6, characterized in that: The surface layer of the multi-layer film is the second film layer.

8. The reflective element according to any one of claims 1 to 7, characterized in that: The reflective substrate is connected to one of the multiple first film layers.

9. The reflective element according to any one of claims 1 to 8, characterized in that: The reflective element is a reflector.

10. An optical device, characterized in that: comprising a light source and a reflective element as claimed in any one of claims 1 to 9; The reflective element is used to reflect the light emitted by the light source and having a wavelength within a preset wavelength band.

11. The optical device according to claim 10, characterized in that The working angle of the reflective element is greater than 0° and less than or equal to 80°.

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