Mirror device, optical device, and laser fusion reactor

Abstract

A mirror device (10) comprises: a first mirror (12) having a first reflective surface (22) on which a light ray (20) falls; and a second mirror (14) disposed away from the first reflective surface (22) in the normal direction to the first reflective surface (22). The second mirror (14) has a second reflective surface (24) on which the light ray (20) falls and a surface (26) opposite to the second reflective surface (24). The opposite surface (26) faces the first reflective surface (22), and the second reflective surface (24) is variable in shape.

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application claims the priority of Japanese Patent Application No. 2023 - 036579 filed on March 9, 2023, and Japanese Patent Application No. 2023 - 074850 filed on April 28, 2023, the entire contents of which are incorporated herein by reference.

[0002] (Technical Field) This disclosure relates to a mirror device, an optical device, and a laser fusion reactor.

Background Art

[0003] X - ray analysis techniques are widely used in academic fields and industries. In recent years, X - ray microscopic spectroscopy imaging for analyzing the local structure of each element of an object using XAFS (X - ray Absorption Fine Structure) and fluorescent X - rays has attracted attention. In X - ray microscopic spectroscopy imaging, since a wide range of X - ray wavelengths are used, an X - ray optical system with less chromatic aberration is required.

[0004] As optical elements used in X - ray optical systems, there are compound refractive lenses that utilize refraction, Fresnel zone plates that utilize diffraction, grazing incidence total reflection mirrors that utilize reflection, etc. Among these, grazing incidence total reflection mirrors have the advantages of high X - ray utilization efficiency and less chromatic aberration. Furthermore, as an optical system without coma aberration, there is an AKB (Advanced Kirkpatrick - Baez) mirror optical system using four grazing incidence total reflection mirrors. Also, in order to make the optical characteristics of the X - ray optical system variable, a shape - variable mirror that attaches a piezoelectric element to a total reflection mirror and controls the shape of the reflection surface according to the deformation amount of the piezoelectric element is also used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In X-ray microspectroscopy imaging, a spatial resolution of about 30 nm has been reported, but further improvement in high spatial resolution is required. To increase the spatial resolution, it is effective to increase the numerical aperture (NA) of the X-ray optical system. However, when trying to increase the numerical aperture, the grazing incidence angle of X-rays in the grazing incidence total reflection mirror increases, and the total reflection condition cannot be satisfied. By using a multilayer mirror that utilizes Bragg reflection, the grazing incidence angle of X-rays can be increased, but chromatic aberration occurs.

[0007] The present disclosure has been made in view of such problems, and one of its exemplary purposes is to provide a technique for improving the numerical aperture of an optical system with less chromatic aberration.

Means for Solving the Problems

[0008] A mirror device according to an aspect of the present disclosure includes a first mirror having a first reflection surface on which light rays are incident, and a second mirror positioned away from the first reflection surface in the normal direction of the first reflection surface. The second mirror has a second reflection surface on which light rays are incident and a surface opposite to the second reflection surface, the opposite surface faces the first reflection surface, and the second reflection surface is shape-variable.

[0009] A mirror device according to another aspect of the present disclosure includes a piezoelectric substrate having a reflection surface on which light rays are incident and a surface opposite to the reflection surface, a first electrode provided on the reflection surface, a second electrode provided on the opposite surface, and a power source for applying a voltage between the first electrode and the second electrode. The piezoelectric substrate includes a first piezoelectric layer having the reflection surface and a second piezoelectric layer having the opposite surface. The second piezoelectric layer is made of the same material as the first piezoelectric layer and has a polarization direction opposite to that of the first piezoelectric layer.

[0010] An optical device according to still another aspect of the present disclosure includes an optical system including a mirror device according to an aspect of the present disclosure, and a detection unit that detects light rays emitted from the optical system.

[0011] Another aspect of the optical device according to the present disclosure includes an optical system including a mirror device according to an aspect of the present disclosure, and a sample holding unit that holds a sample irradiated with a light beam emitted from the optical system.

[0012] Another aspect of the optical device according to the present disclosure includes a laser light source that outputs laser light, a deformable mirror that compensates for the wavefront of the laser light, and a condensing optical element that condenses the laser light reflected by the deformable mirror. The deformable mirror has a reflecting surface on which the laser light is incident and a surface opposite to the reflecting surface, and includes a piezoelectric substrate made of single-crystalline lithium niobate (LN), a first electrode provided on the reflecting surface, a second electrode provided on the opposite surface, a dielectric multilayer mirror provided on the first electrode and reflecting the laser light, and a power supply that applies a voltage between the first electrode and the second electrode.

[0013] Another aspect of the present disclosure is a laser fusion reactor. This laser fusion reactor includes an optical device according to an aspect of the present disclosure, and a reaction vessel that has an internal space into which the laser light output from the optical device is introduced and that contains fuel in which nuclear fusion occurs by irradiation with the laser light.

[0014] In addition, any combination of the above components, or those obtained by mutually substituting the components and expressions of the present disclosure between methods, systems, etc. are also effective as aspects of the present disclosure.

Advantages of the Invention

[0015] According to an aspect of the present disclosure, the numerical aperture of an optical system with less chromatic aberration can be improved.

Brief Description of the Drawings

[0016]

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Embodiments for Carrying Out the Invention

[0017] Before detailing the present disclosure, an overview will be described. The present disclosure relates to an X-ray mirror device that reflects X-rays. The X-ray mirror device according to the present disclosure includes an outer mirror (also referred to as a first mirror) and an inner mirror (also referred to as a second mirror) disposed between the optical axis and the outer mirror. That is, the X-ray mirror device has a nested structure combining the outer mirror and the inner mirror. According to the present disclosure, by combining the outer mirror and the inner mirror, it is possible to improve the numerical aperture of the X-ray optical system while suppressing the grazing incidence angle of the X-rays incident on each mirror to an angle (for example, 10 mrad) at which total reflection is possible or less.

[0018] In an X-ray optical system, since the grazing incidence angle of the mirror is extremely small, the distance from the optical axis to the outer mirror also becomes extremely small and can be, for example, 5 mm or less. In this case, in order to dispose the inner mirror between the optical axis and the outer mirror, it is necessary to make the inner mirror very thin, for example, having a thickness of 1 mm or less, or 500 μm or less. Further, the shape accuracy of the reflecting surface required in the X-ray optical system is 10 nm or less or 5 nm or less. Therefore, the inner mirror is required to have a very difficult specification of maintaining the shape accuracy of the surface of an extremely thin substrate at 10 nm or less.

[0019] In the present disclosure, the inner mirror is formed of a piezoelectric substrate, and electrodes are formed on both surfaces of the piezoelectric substrate, so that the shape of the reflecting surface formed of the surface of the piezoelectric substrate can be made variable according to the applied voltage. That is, a shape-variable mirror is used as the inner mirror. By using an extremely thin piezoelectric substrate, it becomes possible to dispose the inner mirror in the limited space between the optical axis and the outer mirror. Further, by making the inner mirror a shape-variable mirror, it is possible to compensate for the deviation from the ideal shape of the inner mirror, and improve the shape accuracy of the reflecting surface of the inner mirror using a thin substrate.

[0020] Hereinafter, embodiments for implementing the present disclosure will be described in detail with reference to the drawings. In the description, the same reference numerals are assigned to the same elements, and redundant descriptions will be omitted as appropriate. Also, in order to facilitate understanding of the description, the dimensional ratios of the respective components in each drawing do not necessarily match the actual dimensional ratios.

[0021] In the following embodiments, an X-ray mirror device for reflecting X-rays will be described. However, the present disclosure can be used as a mirror device for reflecting X-rays or light rays having wavelengths different from X-rays. In this case, the light rays may be visible light, infrared light, ultraviolet light, extreme ultraviolet light, or gamma rays having wavelengths shorter than X-rays. The light rays may be laser light. The mirror device can be used in any optical device that utilizes light rays. In the mirror device, the surface on which the light rays are incident may be referred to as the incident surface or the reflection surface.

[0022] (First Embodiment) FIG. 1 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 10 according to the first embodiment. The X-ray mirror device 10 includes an outer mirror (or first mirror) 12 and an inner mirror (or second mirror) 14. The X-ray mirror device 10 is configured to reflect X-rays 20 from the first focal point F1 and focus them on the second focal point F2. In FIG. 1, the straight line connecting the first focal point F1 and the second focal point F2 is defined as the optical axis 18. Also, the direction approaching the optical axis 18 may be referred to as the inner direction, and the direction away from the optical axis 18 may be referred to as the outer direction.

[0023] The X-ray mirror device 10 in FIG. 1 can be used as an objective lens. For example, a sample is placed at the first focal point F1, and the X-rays from the sample are enlarged and imaged at the second focal point F2. An X-ray detection device for detecting an enlarged image (X-ray image) of the sample is arranged at the second focal point F2. The X-ray mirror device 10 increases the total of the angular ranges α1 and α2 of the X-rays 20 from the first focal point F1 that the X-ray mirror device 10 can focus by combining the outer mirror 12 and the inner mirror 14. Thereby, the spatial resolution of the sample to be observed can be improved, and for example, a spatial resolution of 10 nm or less or 5 nm or less can be achieved.

[0024] The outer mirror 12 has an outer reflecting surface (or first reflecting surface) 22 on which the X-ray 20 is obliquely incident. The inner mirror 14 has an inner reflecting surface (or second reflecting surface) 24 on which the X-ray 20 is obliquely incident, and a surface (or back surface) 26 opposite to the inner reflecting surface 24. Each of the outer reflecting surface 22 and the inner reflecting surface 24 is, for example, an elliptical concave surface having two foci that coincide with the first focus F1 and the second focus F2.

[0025] Each of the outer reflecting surface 22 and the inner reflecting surface 24 can be an arc-shaped, elliptical, hyperbolic or parabolic convex or concave surface. Each of the outer reflecting surface 22 and the inner reflecting surface 24 may have curvature only in one direction (for example, the optical axis direction). Each of the outer reflecting surface 22 and the inner reflecting surface 24 may be a surface having curvature in two directions, or may be a flat surface.

[0026] The outer mirror 12 is arranged away from the optical axis 18 and is arranged such that the outer reflecting surface 22 faces inward. The outer mirror 12 is arranged such that the optical axis 18 exists in the normal direction of the outer reflecting surface 22 as viewed from the outer reflecting surface 22.

[0027] The inner mirror 14 is arranged between the optical axis 18 and the outer mirror 12. The inner mirror 14 is arranged such that the inner reflecting surface 24 faces inward and the back surface 26 faces outward. The inner mirror 14 is arranged such that the optical axis 18 exists in the normal direction of the inner reflecting surface 24 as viewed from the inner reflecting surface 24. The inner mirror 14 is arranged away from the outer reflecting surface 22 in the normal direction of the outer reflecting surface 22. The back surface 26 of the inner mirror 14 faces the outer reflecting surface 22.

[0028] The outer reflecting surface 22 and the inner reflecting surface 24 are preferably total internal reflection mirrors with no chromatic aberration. The outer reflecting surface 22 and the inner reflecting surface 24 are composed of, for example, a metal thin film made of a single metal material such as nickel (Ni), chromium (Cr), rhodium (Rh), platinum (Pt), or gold (Au). The outer reflecting surface 22 and the inner reflecting surface 24 preferably do not include a multilayer mirror that uses Bragg reflection in order to avoid chromatic aberration. The multilayer mirror is composed of, for example, a multilayer film in which a plurality of first layers made of heavy elements and a plurality of second layers made of light elements are alternately and periodically laminated.

[0029] The outer reflecting surface 22 and the inner reflecting surface 24 may include a multilayer mirror in applications where chromatic aberration is acceptable. However, in order to mitigate the influence of chromatic aberration, it is preferable that the number of layers of the multilayer mirror (for example, the total number of the number of layers of the first layer and the number of layers of the second layer) be 100 or less, 30 or less, or 15 or less. In applications for measuring X-ray absorption near edge structure (XANES), optical characteristics with chromatic aberration negligible in an energy range of, for example, about ±100 eV are required. In this case, it is preferable that the number of layers of the multilayer mirror be 100 or less. In applications for measuring extended X-ray absorption fine structure (EXAFS), optical characteristics with chromatic aberration negligible in an energy range of, for example, about ±500 eV are required. In this case, it is preferable that the number of layers of the multilayer mirror be 30 or less or 15 or less.

[0030] Note that one of the outer reflecting surface 22 and the inner reflecting surface 24 may be a total internal reflection mirror, and the other may be a multilayer mirror. For example, the outer reflecting surface 22 with a relatively large oblique incidence angle may be a multilayer mirror, and the inner reflecting surface 24 with a relatively small oblique incidence angle may be a total internal reflection mirror.

[0031] The outer reflecting surface 22 reflects the X-ray beam 20a within the first angular range α1 from the first focal point F1 toward the second focal point F2. The first angular range α1 can be expressed as α1 ≒ θ1 - θ2 using the maximum value θ1 and the minimum value θ2 of the grazing incidence angle of the X-rays 20 incident on the outer reflecting surface 22. In order to totally reflect the X-rays 20 at the outer reflecting surface 22, it is necessary to make the maximum value θ1 of the grazing incidence angle less than or equal to the critical angle. The magnitude of the critical angle depends on the energy (i.e., wavelength) of the X-rays 20, and the critical angle becomes smaller as the energy of the X-rays 20 increases. For example, when the energy of the X-rays is 10 keV, the magnitude of the critical angle is approximately 7 mrad. From the viewpoint of maximizing the first angular range α1, it is preferable that the maximum value θ1 of the grazing incidence angle at the outer reflecting surface 22 be as large as possible. Therefore, it is preferable that the maximum value θ1 of the grazing incidence angle at the outer reflecting surface 22 be as close as possible to the critical angle, which is the upper limit value.

[0032] The inner reflecting surface 24 reflects the X-ray beam 20a within the second angular range α2 from the first focal point F1 toward the second focal point F2. The second angular range α2 is an angular range different from the first angular range α1. The second angular range α2 can be expressed as α2 ≒ θ3 - θ4 using the maximum value θ3 and the minimum value θ4 of the grazing incidence angle of the X-rays 20 incident on the inner reflecting surface 24. Since the inner reflecting surface 24 is arranged inside the outer reflecting surface 22, the maximum value θ3 of the grazing incidence angle at the inner reflecting surface 24 is smaller than the maximum value θ1 of the grazing incidence angle at the outer reflecting surface 22. For example, the maximum value θ3 of the grazing incidence angle at the inner reflecting surface 24 can be a value smaller than the critical angle.

[0033] When the oblique incident angle of the X-ray 20 is small, the required shape accuracy of the reflecting surface is relaxed. Therefore, the shape accuracy of the inner reflecting surface 24 may be lower than that of the outer reflecting surface 22. The shape accuracy (PV; Peak-to-Valley) of the outer reflecting surface 22 and the inner reflecting surface 24 is 10 nm or less, or 5 nm or less. The shape accuracy (PV) of the outer reflecting surface 22 is preferably 3 nm or less, for example, about 2 nm. The shape accuracy (PV) of the inner reflecting surface 24 may be 3 nm or more, for example, about 5 nm. The shape accuracy (PV) of the outer reflecting surface 22 and the inner reflecting surface 24 can be achieved by performing known precision machining such as EEM (Elastic Emission Machining) after rough machining by cutting, mechanical polishing, or the like.

[0034] The first distance D1 becomes a small value due to the constraint of making the maximum value θ1 of the oblique incident angle on the outer reflecting surface 22 equal to or less than the critical angle (for example, 10 mrad) and accommodating the X-ray optical system in a practical size (for example, 1 m to 10 m). The first distance D1 from the optical axis 18 to the outer reflecting surface 22 is, for example, 10 mm or less, 5 mm or less, 3 mm or less, or 1 mm or less. The first distance D1 is, for example, 100 μm or more, 200 μm or more, 300 μm or more, or 500 μm or more.

[0035] The first distance D1 corresponds to the sum of the second distance D2 to the inner reflecting surface 24 of the optical axis 18, the thickness t of the inner mirror 14 from the inner reflecting surface 24 to the back surface 26, and the third distance D3 from the inner mirror 14 to the outer reflecting surface 22 (that is, D1 = D2 + t + D3). In order to maximize the sum of the first angular range α1 and the second angular range α2, it is preferable to make the thickness t of the inner mirror 14 as small as possible. The thickness t of the inner mirror 14 is, for example, 1 mm or less, 500 μm or less, 300 μm or less, or 200 μm or less. The thickness t of the inner mirror 14 is, for example, 10 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, or 200 μm or more. Each of the second distance D2 and the third distance D3 is, for example, 50 μm or more, 100 μm or more, 200 μm or more, or 500 μm or more. Each of the second distance D2 and the third distance D3 is, for example, 5 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less. The third distance D3 is, for example, larger than the second distance D2. The third distance D3 may be the same as the second distance D2 or smaller than the second distance D2.

[0036] The inner mirror 14 is configured as a shape-variable mirror using a piezoelectric substrate. By making the inner mirror 14 a shape-variable mirror, it is possible to achieve both an extremely thin thickness t and the shape accuracy of the inner reflecting surface 24. Details of the shape-variable mirror that can be used for the inner mirror 14 will be described separately later. On the other hand, since there is no thickness constraint for the outer mirror 12, any type of mirror can be used as long as the shape accuracy of the outer reflecting surface 22 can be realized.

[0037] The outer mirror 12 may be a shape-variable mirror using a piezoelectric material or a normal mirror that does not use a piezoelectric material (that is, is not shape-variable). When the outer mirror 12 is a normal mirror, it is composed of a substrate of any material that can precisely process the surface shape, such as silicon or glass. When the outer mirror 12 is a shape-variable mirror, a piezoelectric element may be attached to the surface of the substrate having the outer reflecting surface 22, or a piezoelectric substrate having the outer reflecting surface 22 may be used.

[0038] (Second Embodiment) Figure 2 is a cross-sectional view schematically showing the configuration of the shape-variable mirror 30 according to the second embodiment. The shape-variable mirror 30 in FIG. 2 can be used as the inner mirror 14 in FIG. 1. The shape-variable mirror 30 in FIG. 2 may be used as the outer mirror 12 in FIG. 1. The shape-variable mirror 30 includes a piezoelectric substrate 32, a reflecting surface electrode (or first electrode) 34, a back surface electrode (or second electrode) 36, and a power source 38.

[0039] In FIG. 2, the direction orthogonal to both the incident direction and the reflection direction of the X-ray 20 in the shape-variable mirror 30 is defined as the x-direction. Also, the thickness direction of the piezoelectric substrate 32 is defined as the z-direction, and the direction orthogonal to both the x-direction and the z-direction is defined as the y-direction. The y-direction corresponds to the direction in which the optical axis 18 of the X-ray 20 extends (also referred to as the optical axis direction). The illustrated coordinate axes are set for assisting the understanding of the description and do not limit the orientation of the shape-variable mirror 30 during use.

[0040] The piezoelectric substrate 32 has a reflecting surface 40 and a surface (or back surface) 42 opposite to the reflecting surface 40. The reflecting surface electrode 34 is provided on the reflecting surface 40, and the back surface electrode 36 is provided on the back surface 42. The thickness of the piezoelectric substrate 32 is 10 μm or more and 10 mm or less, for example, 50 μm or more and 1 mm or less. The thickness of the piezoelectric substrate 32 may be 100 μm or more, 200 μm or more, or 250 μm or more. The thickness of the piezoelectric substrate 32 may be 500 μm or less, 400 μm or less, or 300 μm or less.

[0041] The piezoelectric substrate 32 is made of a piezoelectric material, for example, a single-crystalline piezoelectric material such as lithium niobate (LN) or lithium tantalate (LT). As the piezoelectric substrate 32, for example, a 127.86-degree Y-cut LN substrate, a 140-degree Y-cut LN substrate, or a 36-degree Y-cut LN substrate can be used.

[0042] The piezoelectric substrate 32 deforms in response to a voltage applied between the reflective surface electrode 34 and the back surface electrode 36. The piezoelectric substrate 32 includes a first piezoelectric layer 44 and a second piezoelectric layer 46. The first piezoelectric layer 44 and the second piezoelectric layer 46 expand and contract in the y direction in response to a voltage applied in the z direction. The first piezoelectric layer 44 and the second piezoelectric layer 46 are made of the same material and have polarization directions opposite to each other. In the example of FIG. 2, the polarization direction A1 of the first piezoelectric layer 44 is the -z direction, and the polarization direction A2 of the second piezoelectric layer 46 is the +z direction. When a voltage is applied so that the first piezoelectric layer 44 expands, the second piezoelectric layer 46 contracts. Conversely, when a voltage is applied so that the first piezoelectric layer 44 contracts, the second piezoelectric layer 46 expands. As a result, the piezoelectric substrate 32 functions like a bimorph type piezoelectric element. The thicknesses of the first piezoelectric layer 44 and the second piezoelectric layer 46 are preferably about the same.

[0043] The piezoelectric substrate 32 can be formed, for example, by preparing two substrates corresponding to the first piezoelectric layer 44 and the second piezoelectric layer 46 respectively, and bonding the two substrates in a direction where their polarization directions are opposite to each other. The first piezoelectric layer 44 and the second piezoelectric layer 46 are preferably bonded by a method that does not use an adhesive such as an optical contact.

[0044] The piezoelectric substrate 32 may be formed by heat-treating a substrate with a constant polarization direction. In an LN substrate or an LT substrate, it is known that a polarization inversion layer with an inverted polarization direction is formed by heat treatment at a temperature near the Curie point.

[0045] Figs. 3(a) to 3(c) are diagrams schematically showing an example of a method for forming the polarization inversion layer 56, showing the case of using an LN substrate. Fig. 3(a) shows the LN substrate 50 before heat treatment. The LN substrate 50 has a plus surface 52 and a minus surface 54. The polarization direction A2 of the LN substrate 50 is a direction from the minus surface 54 toward the plus surface 52. Fig. 3(b) shows the LN substrate 50 during heat treatment. By the heat treatment, a polarization inversion layer 56 is formed in the vicinity of the plus surface 52. The temperature of the heat treatment is, for example, 1100 to 1150°C. The thickness t1 of the polarization inversion layer 56 depends on the heat treatment time, and the thickness t1 increases as the heat treatment time becomes longer. Fig. 3(c) shows the LN substrate 50 after heat treatment. By adjusting the heat treatment time, the thickness t1 of the polarization inversion layer 56 can be made half of the thickness t of the LN substrate 50. For example, when the thickness t of the LN substrate 50 is 200 μm, the heat treatment conditions necessary for making the thickness t1 of the polarization inversion layer 56 100 μm are about 6 hours at 1150°C.

[0046] When using an LT substrate as the piezoelectric substrate 32, before the heat treatment, the LT substrate is immersed in benzoic acid, pyrophosphoric acid, etc., and it is necessary to apply a proton exchange method for exchanging lithium ions (Li + ) on the substrate surface with protons (H + ). After the proton exchange, by heat-treating the LT substrate at 550°C to 600°C, the first piezoelectric layer 44 and the second piezoelectric layer 46 whose polarization directions are opposite to each other can be formed. When using an LT substrate, the polarization direction is opposite to the case of using an LN substrate, the polarization direction of the first piezoelectric layer 44 becomes the +z direction, and the polarization direction of the second piezoelectric layer 46 becomes the -z direction. This is considered to be because protons diffuse into the crystal during the heat treatment, and a polarization inversion layer is formed on the minus surface instead of the plus surface.

[0047] Note that, as the piezoelectric substrate 32, a piezoelectric material that is not of the bimorph type may be used. In this case, the entire polarization direction of the piezoelectric substrate 32 may be uniform. When the piezoelectric substrate 32 is not of the bimorph type, the piezoelectric substrate 32 may be configured to expand and contract in the z direction in response to the voltage applied in the z direction.

[0048] Returning to FIG. 2, the reflecting surface 40 has the shape accuracy and surface roughness required for an oblique-incidence total reflection mirror. The shape accuracy (PV) of the reflecting surface 40 is, for example, 10 nm or less, preferably 2 nm or more and 5 nm or less. The surface roughness (Rms) of the reflecting surface 40 is, for example, 0.5 nm or less, preferably 0.05 nm or more and 0.2 nm or less.

[0049] The reflecting surface 40 is, for example, a convex or concave curved surface in the shape of an arc, an ellipse, a hyperbola, or a parabola, and has curvature in only one direction (for example, the y direction). In the example of FIG. 2, the reflecting surface 40 is a concave curved surface. The reflecting surface 40 may be a flat surface, or may be a curved surface having curvature in two directions (for example, the x direction and the y direction). The back surface 42 is, for example, a polished flat surface.

[0050] The reflecting surface electrode 34 is provided on the reflecting surface 40. The reflecting surface electrode 34 has a thickness of, for example, 10 nm or more and 100 nm or less. The reflecting surface electrode 34 is provided so as to cover, for example, the entire reflecting surface 40 and have a uniform thickness over the entire reflecting surface 40. Since the reflecting surface electrode 34 has a uniform thickness, the surface of the reflecting surface electrode 34 has a shape corresponding to the reflecting surface 40 and has the same shape accuracy and surface roughness as the reflecting surface 40. The reflecting surface electrode 34 functions as an electrode for applying a voltage to the piezoelectric substrate 32 and also functions as a total reflection mirror that totally reflects the X-rays 20.

[0051] As the material of the reflecting surface electrode 34, nickel (Ni), chromium (Cr), rhodium (Rh), platinum (Pt), gold (Au), etc. can be used. The reflecting surface electrode 34 may be composed of a single-material metal thin film, or may be composed of a laminate of a plurality of metal thin films having different materials. The reflecting surface electrode 34 may have, for example, an adhesion layer such as Cr or Ti that contacts the reflecting surface 40, and a reflection layer such as Rh, Pt, or Au formed on the adhesion layer. The reflecting surface electrode 34 can be formed using a vapor deposition method or a sputtering method.

[0052] The back electrode 36 is provided on the back surface 42. The back electrode 36 includes a plurality of electrodes 36a, 36b, 36c, 36d, 36e, 36f, 36g, 36h, 36i arranged at intervals in the optical axis direction (for example, the y direction). The width w of the plurality of electrodes 36a to 36i in the optical axis direction (for example, the y direction) is, for example, 0.5 mm or more and 10 mm or less, preferably 1 mm or more and 6 mm or less. The interval d of the plurality of electrodes 36a to 36i in the optical axis direction (for example, the y direction) is, for example, 0.1 mm or more and 5 mm or less, preferably 0.5 mm or more and 4 mm or less. The pitch p (the sum of the width w and the interval d) of the plurality of electrodes 36a to 36i in the optical axis direction (for example, the y direction) is, for example, 1 mm or more and 15 mm or less, preferably 1.5 mm or more and 10 mm or less.

[0053] The plurality of electrodes 36a to 36i are configured such that, for example, the width w, the interval d, and the pitch p in the optical axis direction (for example, the y direction) are constant. At least one of the width w, the interval d, and the pitch p of each of the plurality of electrodes 36a to 36i may be configured to be different from each other. For example, when the angle θ of the X-ray 20 obliquely incident on the reflecting surface 40 varies depending on the position in the optical axis direction, the pitch p of the plurality of electrodes 36a to 36i may be made different from each other so that the effective pitch p×θ as seen from the X-ray 20 is constant.

[0054] The back electrode 36 is made of a metal material, and for example, nickel (Ni), chromium (Cr), copper (Cu), silver (Ag), gold (Au), etc. can be used. The thickness of the back electrode 36 is not particularly limited, but is, for example, 100 nm or more and 1000 nm or less.

[0055] The power supply 38 applies a DC voltage between the reflective surface electrode 34 and the back surface electrode 36. The power supply 38 is configured to be able to apply different voltages to each of the plurality of electrodes 36a to 36i. In FIG. 2, to prevent complication of the drawing, the power supply 38 is connected only to one electrode 36a out of the plurality of electrodes 36a to 36i. Actually, the power supply 38 is connected to each of the plurality of electrodes 36a to 36i. The power supply 38 is configured to independently control the voltages applied to each of the plurality of electrodes 36a to 36i. The power supply 38 applies a DC voltage that is variable, for example, in the range from -1 kV to +1 kV. By variably controlling the applied voltage of each of the plurality of electrodes 36a to 36i individually, the power supply 38 controls the amount of deformation of the piezoelectric substrate 32 at the position corresponding to each of the plurality of electrodes 36a to 36i, and variably controls the shape of the reflective surface 40.

[0056] FIG. 4 is a graph showing an example of the amount of deformation of the reflective surface 40 of the shape-variable mirror 30. FIG. 4 is based on the height of the reflective surface 40 when no voltage is applied to the plurality of electrodes 36a to 36i, and shows the amount of deformation of the reflective surface 40 when the magnitudes of the applied voltages of the plurality of electrodes 36a to 36i are 10 V, 20 V, 30 V, 40 V, 50 V, and 100 V. The applied voltages of the plurality of electrodes 36a to 36i alternately change the positive and negative in the optical axis direction (for example, the y direction). The vertical axis of the graph is the amount of deformation [nm] in the thickness direction (z direction), and the horizontal axis of the graph is the position [mm] in the optical axis direction (for example, the y direction). In the embodiment of FIG. 4, the width w of the plurality of electrodes 36a to 36i is 5 mm, and the interval d is 1 mm. As the piezoelectric substrate 32, a 250-μm-thick bimorph-type LN substrate is used.

[0057] As shown in FIG. 4, the convex and concave portions of the deformed reflecting surface 40 occur approximately every 6 mm, and it can be seen that the reflecting surface 40 can be deformed so as to correspond to the positions of a plurality of electrodes 36a to 36i arranged at a pitch of 6 mm. When the magnitude of the applied voltage to the plurality of electrodes 36a to 36i is 100 V, the height difference between the convex and concave portions is approximately 1 mm, and a large amount of deformation due to the bimorph type can be realized. Also, it can be seen that there is a high linearity between the applied voltage and the amount of deformation. Further, no hysteresis such as that present in piezoelectric ceramic materials such as PZT is observed, and no drift is observed in which the amount of deformation changes over time despite the applied voltage being fixed. Therefore, according to the shape-variable mirror 30 according to the present embodiment, the amount of deformation can be uniquely determined according to the applied voltage, and the shape of the reflecting surface 40 can be stably controlled with high reproducibility.

[0058] According to the present embodiment, since the shape of the reflecting surface 40 can be variably controlled while irradiating the reflecting surface 40 with the X-rays 20, the shape of the reflecting surface 40 can be adjusted retrospectively so as to be optimal in the X-ray mirror device 10 in which the shape-variable mirror 30 is incorporated. For example, by measuring the shape of the reflecting surface 40 by the pencil beam method using X-rays, in a state where the shape-variable mirror 30 is applied to the X-ray mirror device 10, the measurement and adjustment of the shape of the reflecting surface 40 can be precisely performed on-site.

[0059] When the shape-variable mirror 30 is used as the inner mirror 14, since the thickness of the piezoelectric substrate 32 is very small, distortion due to the supporting force for supporting the inner mirror 14 may occur on the inner reflecting surface 24. According to the present embodiment, since the inner mirror 14 is the shape-variable mirror 30, the distortion caused by the supporting force of the inner reflecting surface 24 can be compensated, and the inner reflecting surface 24 can be deformed so as to have an ideal shape. For example, by predicting with high accuracy the distortion of the inner reflecting surface 24 caused by the supporting force of the inner mirror 14 by simulation such as the finite element method, the distortion can be compensated with high accuracy.

[0060] (Third Embodiment) FIG. 5 is a top view schematically showing the configuration of the shape-variable mirror 30A according to the third embodiment. In the third embodiment, a reflective surface electrode 33 and a reflective film 35 are provided on the reflective surface 40 of the piezoelectric substrate 32. The reflective surface electrode 33 includes a plurality of electrodes 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, 33i arranged at intervals in the optical axis direction (for example, the y direction). In this embodiment, the differences from the above-described embodiment will be mainly described, and the common points will be omitted as appropriate.

[0061] The shape-variable mirror 30A includes a piezoelectric substrate 32, a reflective surface electrode 33, a reflective film 35, a back surface electrode 36 (see FIG. 2), and a power supply 38 (see FIG. 2). The reflective surface electrode 33 and the reflective film 35 are provided on the reflective surface 40 of the piezoelectric substrate 32. The reflective film 35 is disposed at the central portion in the x direction of the reflective surface 40 where the X-rays 20 are incident. The reflective film 35 functions as a total reflection mirror that totally reflects the X-rays 20. The reflective film 35 can be configured with the same material and thickness as the reflective surface electrode 34 according to the above-described embodiment.

[0062] The reflective surface electrode 33 is disposed on both sides in the x direction with the reflective film 35 interposed therebetween. The reflective surface electrode 33 is disposed away from the reflective film 35 in the x direction. The reflective surface electrode 33 includes a plurality of electrodes 33a to 33i. The plurality of electrodes 33a to 33i can have the same width w, interval d, and pitch p as the plurality of electrodes 36a to 36i of the back surface electrode 36 according to the above-described embodiment. The reflective surface electrode 33 can be configured with the same material and thickness as the reflective surface electrode 34 according to the above-described embodiment. The reflective surface electrode 33 may be configured with the same material and thickness as the back surface electrode 36 according to the above-described embodiment.

[0063] In this embodiment, the back surface electrode 36 can include a plurality of electrodes 36a to 36i in the same manner as in the above-described embodiment. In this case, it is preferable that the width w, interval d, and pitch p of the plurality of electrodes 36a to 36i of the back surface electrode 36 are common to the width w, interval d, and pitch p of the plurality of electrodes 33a to 33i of the reflective surface electrode 33.

[0064] In this embodiment, the back electrode 36 does not necessarily include the plurality of electrodes 36a to 36i similar to those in the above-described embodiment. In this case, the back electrode 36 may be uniformly formed over the entire back surface 42 (see FIG. 2) of the piezoelectric substrate 32 and function as a common electrode.

[0065] The power supply 38 is configured to be able to apply different voltages to each of the plurality of electrodes 33a to 33i of the reflecting surface electrode 33. When the back electrode 36 includes the plurality of electrodes 36a to 36i, the power supply 38 applies a voltage between pairs of opposing electrodes of the reflecting surface electrode 33 and the back electrode 36 (for example, a pair of the electrode 33a and the electrode 36a, a pair of the electrode 33b and the electrode 36b, etc.).

[0066] Also in this embodiment, the same effects as those in the above-described embodiment can be achieved.

[0067] (Fourth Embodiment) FIG. 6 is a cross-sectional view schematically showing the configuration of the shape-variable mirror 30B according to the fourth embodiment. In the fourth embodiment, an intermediate electrode 48 is further provided between the first piezoelectric layer 44B and the second piezoelectric layer 46B. In this embodiment, the description will focus on the differences from the above-described embodiment, and the description of the common points will be omitted as appropriate.

[0068] The shape-variable mirror 30B includes a piezoelectric substrate 32B, a reflecting surface electrode (or first electrode) 34, a back electrode (or second electrode) 37, a power supply 38B, and an intermediate electrode 48 (or third electrode). The reflecting surface electrode 34 is configured in the same manner as in the above-described embodiment. The back electrode 37 is uniformly formed over the entire back surface 42 of the piezoelectric substrate 32 and functions as a common electrode.

[0069] The piezoelectric substrate 32B includes a first piezoelectric layer 44B and a second piezoelectric layer 46B, and an intermediate electrode 48 is provided between the first piezoelectric layer 44B and the second piezoelectric layer 46B. The first piezoelectric layer 44B and the second piezoelectric layer 46B are made of the same material and have the same polarization direction. In the example of FIG. 6, the polarization direction B1 of the first piezoelectric layer 44B is the -z direction, and the polarization direction B2 of the second piezoelectric layer 46B is also the -z direction. The polarization directions B1 and B2 of the first piezoelectric layer 44B and the second piezoelectric layer 46B are not limited to those shown, and may be, for example, the +z direction.

[0070] The intermediate electrode 48 includes a plurality of electrodes 48a, 48b, 48c, 48d, 48e, 48f, 48g, 48h, 48i arranged at intervals in the optical axis direction (for example, the y direction). The plurality of electrodes 48a to 48i can have the same width w, interval d, and pitch p as the plurality of electrodes 36a to 36i of the back electrode 36 according to the above-described embodiment. The intermediate electrode 48 can be formed of the same material and thickness as the reflective surface electrode 34 and the back electrode 36 according to the above-described embodiment.

[0071] The intermediate electrode 48 can be formed, for example, by using a vapor deposition method or a sputtering method to form a first metal film on the bonding surface of the first piezoelectric layer 44B and a second metal film on the bonding surface of the second piezoelectric layer 46B, and then joining the first metal film and the second metal film. The joining method of the first metal film and the second metal film is not particularly limited, and any joining technique can be used. As an example, a solid-phase joining technique such as room-temperature joining or diffusion joining can be used. Alternatively, the first metal film and the second metal film may be electrically and mechanically joined using a binder material such as a conductive adhesive or metal nanoparticles. The first metal film and the second metal film may be mechanically joined by an insulating adhesive or adhesive layer. The intermediate electrode 48 may be composed of a metal film formed only on one bonding surface of the first piezoelectric layer 44B or the second piezoelectric layer 46B. In these cases, the joining method between the first piezoelectric layer 44B and the second piezoelectric layer 46B is not particularly limited, and an adhesive or adhesive layer of any material may be used, or a joining method without using an adhesive may be used.

[0072] Power supply 38B applies a DC voltage between the reflective surface electrode 34 and the intermediate electrode 48, and also applies a DC voltage between the intermediate electrode 48 and the back surface electrode 37. In the example of FIG. 6, the power supply 38B is connected such that the potentials of the reflective surface electrode 34 and the back surface electrode 37 are common. In a modified example, a second power supply that applies a DC voltage between the intermediate electrode 48 and the back surface electrode 37 may be used separately from the first power supply that applies a DC voltage between the reflective surface electrode 34 and the intermediate electrode 48. That is, the first applied voltage between the reflective surface electrode 34 and the intermediate electrode 48 and the second applied voltage between the intermediate electrode 48 and the back surface electrode 37 may be controllable individually.

[0073] In the example of FIG. 6, the direction of the electric field applied to the first piezoelectric layer 44B and the direction of the electric field applied to the second piezoelectric layer 46B are opposite up and down. Since the polarization directions of the first piezoelectric layer 44B and the second piezoelectric layer 46B are the same, they function like a bimorph-type piezoelectric element when voltages in opposite directions are applied to each other.

[0074] Also in this embodiment, the same effects as those of the above-described embodiment can be realized.

[0075] In a modified example of the configuration of FIG. 6, the reflective surface electrode 33 and the reflective film 35 shown in FIG. 5 may be provided on the reflective surface 40 of the first piezoelectric layer 44B. That is, a plurality of electrodes 33a to 33i may be provided on the reflective surface 40 of the first piezoelectric layer 44B. Further, the back surface electrode 36 according to the above-described embodiment may be provided on the back surface 42 of the second piezoelectric layer 46B. That is, a plurality of electrodes 36a to 36i may be provided on the back surface 42 of the second piezoelectric layer 46B. In this case, the intermediate electrode 48 may include a plurality of electrodes 48a to 48i, or may not include a plurality of electrodes 48a to 48i. In the latter case, the intermediate electrode 48 may function as a common electrode formed on the entire bonding surface of the first piezoelectric layer 44B and the second piezoelectric layer 46B. The power supply 38B may be configured to be able to apply different voltages to each of the plurality of electrodes 33a to 33i of the reflective surface electrode 33. The power supply 38B may be configured to be able to apply different voltages to each of the plurality of electrodes 36a to 36i of the back surface electrode 36.

[0076] (Fifth Embodiment) FIG. 7 is a bottom view schematically showing the configuration of the shape-variable mirror 30C according to the fifth embodiment. In the fifth embodiment, the back electrodes 36 are arranged in a two-dimensional array in the x-direction and the y-direction. In the fifth embodiment, by applying different voltages to each of the two-dimensional array of back electrodes 36, the shape of the reflecting surface 40 can be variably controlled two-dimensionally. In the example shown in FIG. 7, the outer shape of the piezoelectric substrate 32 is circular, but the outer shape of the substrate 32 is not particularly limited. The outer shape of the piezoelectric substrate 32 may be rectangular.

[0077] (Sixth Embodiment) FIG. 8 is a bottom view schematically showing the configuration of the shape-variable mirror 30D according to the sixth embodiment. In the sixth embodiment, the outer shape of the piezoelectric substrate 32 is circular, and the back electrodes 36 are arranged in a two-dimensional array in the radial direction and the circumferential direction. Also in the sixth embodiment, by applying different voltages to each of the two-dimensional array of back electrodes 36, the shape of the reflecting surface 40 can be variably controlled two-dimensionally.

[0078] (Seventh Embodiment) FIG. 9 is a cross-sectional view schematically showing the configuration of the shape-variable mirror 30E according to the seventh embodiment. The seventh embodiment is different from the above-described embodiments in that a multilayer mirror 58 is further provided on the reflecting surface electrode 34. For this embodiment, the description will be centered on the differences from the above-described embodiments, and the description of the common points will be omitted as appropriate.

[0079] The shape-variable mirror 30E includes a piezoelectric substrate 32, a reflective surface electrode 34, a back surface electrode 36, a power supply 38, and a multilayer mirror 58. The multilayer mirror 58 is configured to reflect the light beam 20E incident on the multilayer mirror 58 with a high reflectivity. When the light beam 20E is ultraviolet light, visible light, or infrared light, the multilayer mirror 58 may be a dielectric multilayer film, and may be configured such that the reflectivity of the light beam 20E is 99% or more, for example, 99.9% or more. The material of the dielectric multilayer film is not particularly limited, but oxide materials such as Al2O3, SiO2, HfO2, and fluoride materials such as LaF3, MgF2, AlF3 can be used. The thickness of the multilayer mirror 58 is not particularly limited, but is, for example, smaller than the thickness of the piezoelectric substrate 32. The thickness of the multilayer mirror 58 is, for example, 1 μm or more, 5 μm or more, or 10 μm or less, and is, for example, 50 μm or less, 20 μm or less, or 10 μm or less.

[0080] The shape-variable mirror 30E does not include an additional dielectric layer between the reflective surface electrode 34 and the multilayer mirror 58. Therefore, the thickness of the dielectric material included between the reflective surface 40 of the piezoelectric substrate 32 and the upper surface 59 of the multilayer mirror 58 coincides with the thickness of the multilayer mirror 58. The shape-variable mirror 30E may include an additional dielectric layer between the reflective surface electrode 34 and the multilayer mirror 58. As the material of the additional dielectric layer, the same materials as those of the dielectric multilayer film can be used. The thickness of the additional dielectric layer is, for example, 1 μm or more, 5 μm or more, or 10 μm or less, and is, for example, 50 μm or less, 20 μm or less, or 10 μm or less. In these cases, the thickness from the reflective surface 40 of the piezoelectric substrate 32 to the upper surface 59 of the multilayer mirror 58 is 1 mm or less, and is, for example, 200 μm or less, 100 μm or less, or 50 μm or less.

[0081] (Eighth Embodiment) FIG. 10 is a top view schematically showing the configuration of the shape-variable mirror 30F according to the eighth embodiment. In the eighth embodiment, similar to the third embodiment shown in FIG. 5, a reflective surface electrode 33 and a reflective film 35 are provided on the reflective surface 40 of the piezoelectric substrate 32. The eighth embodiment is different from the third embodiment in that the outer peripheral shapes of the reflective surface electrode 33 and the reflective film 35 are rounded polygons. In this embodiment, the differences from the above-described embodiments will be mainly described, and the common points will be omitted as appropriate.

[0082] The outer peripheral shape of each of the plurality of electrodes 33a to 33h constituting the reflective surface electrode 33 is a polygon with rounded corners 33r, for example, a rectangle with rounded corners 33r. The radius of curvature of the corner 33r of each of the electrodes 33a to 33h is, for example, 1% or more, 5% or more, or 10% or more of the width w in the optical axis direction (for example, the y direction) of each of the electrodes 33a to 33h, and is 50% or less, 30% or less, or 20% or less of the width w. By rounding the corners 33r of each of the electrodes 33a to 33h constituting the reflective surface electrode 33, the electric field concentration at the corners 33r can be alleviated, and the discharge that may occur when a high voltage is applied can be suppressed.

[0083] The outer peripheral shape of the reflective film 35 is a polygon with rounded corners 35r, for example, a rectangle with rounded corners 35r. The radius of curvature of the corner 35r of the reflective film 35 is the same as or larger than the radius of curvature of the corner 33r of each of the electrodes 33a to 33h constituting the reflective surface electrode 33. The radius of curvature of the corner 35r of the reflective film 35 is, for example, 1% or more, 5% or more, or 10% or more of the width w in the optical axis direction (for example, the y direction) of each of the electrodes 33a to 33h, and is 100% or less, 50% or less, or 30% or less of the width w. By rounding the corners 35r of the reflective film 35, the electric field concentration at the corners 35r can be alleviated, and the discharge that may occur between the reflective surface electrode 33 and the reflective film 35 can be suppressed.

[0084] In addition, in the deformable mirrors 30, 30A, 30B, 30C, 30D, 30E according to other embodiments, at least one outer peripheral shape of the reflecting surface electrode (or the first electrode) 33, 34, the reflecting film 35, and the back surface electrode (or the second electrode) 36, 37 may be a polygon or a rectangle with rounded corners. For example, in the deformable mirrors 30C, 30E shown in FIGS. 7 and 8, the corners of the back surface electrode 36 may be rounded.

[0085] FIG. 11 is a graph showing an example of the deformation amount of the reflecting surface of the deformable mirror 30F. The curve G1 shown by the dashed line indicates the surface shape of the reflecting film 35 when no voltage is applied to the plurality of electrodes 33a to 33h of the deformable mirror 30F. The curve G2 shown by the solid line indicates the surface shape of the reflecting film 35 when a predetermined voltage is applied to the plurality of electrodes 33a to 33h of the deformable mirror 30F. The vertical axis of the graph indicates the error from the ideal shape of the surface of the reflecting film 35. The shape accuracy (PV) before voltage application shown by the curve G1 is about 140 nm. On the other hand, the shape accuracy (PV) after voltage application shown by the curve G2 is 3 nm, and it can be seen that a preferable shape accuracy as an X-ray mirror is achieved.

[0086] Note that the shape accuracy shown in FIG. 11 can be achieved not only in the deformable mirror 30F according to the present embodiment but also in the deformable mirrors 30, 30A, 30B, 30C, 30D, 30E according to other embodiments.

[0087] FIGS. 12(a) and (b) are diagrams schematically showing operation examples of the deformable mirror 30F. FIG. 12(a) shows a case where the reflecting surface 40 of the deformable mirror 30F is a concave curved surface and the X-rays 20 incident on the reflecting surface 40 are focused on a specific point 39a of the sample 39. FIG. 12(b) shows a case where the reflecting surface 40 of the deformable mirror 30F is a convex curved surface and the X-rays 20 incident on the reflecting surface 40 are diverged toward a wide range 39b of the sample 39.

[0088] The deformable mirror 30F according to this embodiment has a large amount of deformation of the reflecting surface 40 in response to changes in the voltage applied to the plurality of electrodes 33a to 33h. Therefore, by simply changing the voltage, the state shown in Fig. 12(a) and the state shown in Fig. 12(b) can be switched. In the state of Fig. 12(a), the beam width of the X-ray 20 at the specific point 39a can be focused to about 200 nm. On the other hand, in the state of Fig. 12(b), the size of the range 39b irradiated with the X-ray 20 can be diverged to 1 mm or more or 10 mm or more. For example, while the sample 39 is fixed, it is possible to switch between a focusing mode in which the X-ray 20 is irradiated only on the specific point 39a of the sample 39 and a diverging mode in which the X-ray 20 is irradiated on a wide range 39b of the sample 39. Thereby, the local measurement and the overall measurement of the sample 39 can be instantaneously switched, improving the convenience for the user.

[0089] Note that the operation examples shown in Figs. 12(a) and (b) can be realized not only in the deformable mirror 30F according to this embodiment but also in the deformable mirrors 30, 30A, 30B, 30C, 30D, 30E according to other embodiments.

[0090] (Ninth Embodiment) Fig. 13 is a cross-sectional view schematically showing the configuration of the X-ray mirror device 10A according to the ninth embodiment. In the ninth embodiment, it is different from the X-ray mirror device 10 in Fig. 1 in that the thickness of the inner mirror 14A is configured to change in a tapered shape in the optical axis direction. Hereinafter, this embodiment will be described centering on the differences from the above-described embodiments, and the description of the common points will be omitted as appropriate.

[0091] The X-ray mirror device 10A includes an outer mirror 12 and an inner mirror 14A. The outer mirror 12 is configured in the same manner as in the above-described embodiments. The inner mirror 14A includes an inner reflecting surface 24A and a back surface 26A. The inner reflecting surface 24A can be configured in the same manner as the inner reflecting surface 24 in the above-described embodiments.

[0092] The inner mirror 14A has a first end 25 located on the incident side of the X-ray 20 (the first focal point F1 side) and a second end 27 located on the exit side of the X-ray 20 (the second focal point F2 side). The inner mirror 14A extends along the optical axis 18 from the first end 25 toward the second end 27. The inner mirror 14A is configured such that the thickness ta of the first end 25 is different from the thickness tb of the second end 27, and the thickness changes in a tapered shape from the first end 25 toward the second end 27. The thickness of the inner mirror 14A is configured to increase or decrease monotonically in the optical axis direction. In the example of FIG. 13, the thickness ta of the first end 25 is smaller than the thickness tb of the second end 27, and the thickness is configured to increase monotonically from the first end 25 toward the second end 27. In an example different from FIG. 13, the thickness ta of the first end 25 may be larger than the thickness tb of the second end 27, and the thickness may be configured to decrease monotonically from the first end 25 toward the second end 27.

[0093] According to the present embodiment, by changing the thickness of the inner mirror 14A in a tapered shape, the thickness ta of the first end 25 or the thickness tb of the second end 27 can be made smaller than in the case where the thickness is constant. As a result, the angular range δ of the X-ray 20 that cannot be effectively used because it is shielded by the inner mirror 14A can be reduced, and the first angular range α1 can be made larger. The angular range δ that cannot be effectively used is, for example, the range between the first angular range α1 and the second angular range α2. Thereby, the numerical aperture of the X-ray mirror device 10A can be further improved, and the spatial resolution can be improved.

[0094] In the example of FIG. 13, since the distance from the X-ray mirror device 10A to the first focal point F1 is closer than the distance to the second focal point F2, the angular ranges α1 and α2 of the X-ray beams 20a and 20b incident on the X-ray mirror device 10A are relatively large, and the angular ranges β1 and β2 of the X-ray beams 20c and 20d emitted from the X-ray mirror device 10A are relatively small. In such a case, the space between the X-ray beam 20a incident on the outer mirror 12 and the X-ray beam 20b incident on the inner mirror 14A is particularly limited. On the other hand, there is a relatively large margin in the space between the X-ray beam 20c emitted from the outer mirror 12 and the X-ray beam 20d emitted from the inner mirror 14A. In the example of FIG. 13, by reducing the thickness ta of the first end portion 25, it is possible to prevent the X-ray beam 20a in the first angular range α1 from being blocked by the inner mirror 14A, contributing to an improvement in the numerical aperture of the X-ray mirror device 10A. Further, by increasing the thickness tb of the second end portion 27, the mechanical strength of the inner mirror 14A can be improved.

[0095] Conversely, in the case of a configuration where the distance from the X-ray mirror device 10A to the second focal point F2 is closer than the distance to the first focal point F1, contrary to the example of FIG. 13, the thickness ta of the first end portion 25 can be increased and the thickness tb of the second end portion 27 can be reduced. Thereby, it is possible to achieve both an improvement in the numerical aperture of the X-ray mirror device 10A and an improvement in the mechanical strength of the inner mirror 14A.

[0096] (Tenth Embodiment) FIG. 14 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 110 according to the tenth embodiment. The X-ray mirror device 110 includes an outer mirror (or first mirror) 112, an inner mirror (or second mirror) 114, and an intermediate mirror 116 (or third mirror). In the tenth embodiment, it is different from the first embodiment described above in that an intermediate mirror 116 is added between the outer mirror 112 and the inner mirror 114. Hereinafter, the tenth embodiment will be described centering on the differences from the above-described embodiments, and the description of the common points will be omitted as appropriate.

[0097] The outer mirror 112 has an outer reflecting surface (or first reflecting surface) 122 on which the X-rays 120 are obliquely incident. The outer reflecting surface 122 reflects an X-ray beam 120a within a first angular range α1 from the first focal point F1 toward the second focal point F2. The outer mirror 112 can be configured in the same manner as the outer mirror 12 according to the first embodiment described above.

[0098] The inner mirror 114 has an inner reflecting surface (or second reflecting surface) 124 on which the X-rays 120 are obliquely incident, and a surface (or back surface) 126 opposite to the inner reflecting surface 124. The inner reflecting surface 124 reflects an X-ray beam 120b within a second angular range α2 from the first focal point F1 toward the second focal point F2. The inner mirror 114 can be configured in the same manner as the inner mirror 14 according to the first embodiment described above.

[0099] The intermediate mirror 116 has an intermediate reflecting surface (or third reflecting surface) 128 on which the X-rays 120 are obliquely incident, and a surface (or back surface) 130 opposite to the intermediate reflecting surface 128. The intermediate reflecting surface 128 reflects an X-ray beam 120c within a third angular range α3 from the first focal point F1 toward the second focal point F2. The third angular range α3 is an angular range different from the first angular range α1 and the second angular range α2. The intermediate mirror 116 is disposed between the outer mirror 112 and the inner mirror 114. The intermediate reflecting surface 128 of the intermediate mirror 116 faces the inner mirror 114. The back surface 130 of the intermediate mirror 116 faces the outer mirror 112.

[0100] Similar to the inner mirror 114, due to restrictions on the arrangement space, the intermediate mirror 116 needs to have a reduced thickness. Similar to the inner mirror 114, it is preferable that the shape accuracy (PV) of the intermediate reflecting surface 128 of the intermediate mirror 116 be 10 nm or less, or 5 nm or less. By configuring the intermediate mirror 116 in the same manner as the inner mirror 114, it is possible to achieve both an extremely thin thickness and the shape accuracy of the intermediate reflecting surface 128. As the intermediate mirror 116, for example, the deformable mirrors 30, 30A, 30B shown in FIGS. 2, 5, or 6 can be used.

[0101] According to this embodiment, by forming the X-ray mirror device 110 into a nested structure combining three mirrors, the total of the angular ranges α1, α2, α3 of the X-rays 120 from the first focal point F1 at which the X-ray mirror device 110 can be focused (i.e., the numerical aperture) can be increased. As a result, the spatial resolution can be improved, and for example, a spatial resolution of 10 nm or less or 5 nm or less can be achieved.

[0102] In a modification, a plurality of intermediate mirrors may be arranged between the outer mirror 112 and the inner mirror 114. Further, shape-variable mirrors 30, 30A, 30B can be used as the plurality of intermediate mirrors arranged between the outer mirror 112 and the inner mirror 114. Thereby, for each of the plurality of intermediate mirrors, it is possible to achieve both an extremely thin thickness and high shape accuracy of the reflecting surface.

[0103] In a modification, similar to the inner mirror 14A shown in FIG. 13, the thickness of at least one of the inner mirror 114 and the intermediate mirror 116 may be changed in a tapered shape. Only the thickness of the inner mirror 114 may be changed in a tapered shape, only the thickness of the intermediate mirror 116 may be changed in a tapered shape, or the thicknesses of both the inner mirror 114 and the intermediate mirror 116 may be changed in a tapered shape. Further, the thicknesses of the plurality of intermediate mirrors arranged between the outer mirror 112 and the inner mirror 114 may be changed in a tapered shape.

[0104] (11th Embodiment) FIG. 15 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 210 according to the 11th embodiment. The X-ray mirror device 210 includes a first outer mirror (or first mirror) 212, a first inner mirror (or second mirror) 214, a second outer mirror (or fourth mirror) 232, and a second inner mirror (or fifth mirror) 234. The 3rd embodiment is different from the above-described embodiments in that outer mirrors and inner mirrors are arranged on both sides sandwiching the optical axis 218. Hereinafter, the 11th embodiment will be described centering on the differences from the above-described embodiments, and the description of the common points will be omitted as appropriate.

[0105] The first outer mirror 212 has a first outer reflecting surface (or first reflecting surface) 222 on which the X-rays 220 are obliquely incident. The first outer reflecting surface 222 reflects an X-ray beam 220a within a first angular range α1 from the first focal point F1 toward the second focal point F2. The first outer mirror 212 can be configured in the same manner as the outer mirror 12 according to the above-described first embodiment.

[0106] The first inner mirror 214 has a first inner reflecting surface (or second reflecting surface) 224 on which the X-rays 220 are obliquely incident, and a surface (or first back surface) 226 on the side opposite to the first inner reflecting surface 224. The first inner reflecting surface 224 reflects an X-ray beam 220b within a second angular range α2 from the first focal point F1 toward the second focal point F2. The first inner mirror 214 can be configured in the same manner as the inner mirror 14 according to the above-described first embodiment.

[0107] The second outer mirror 232 is disposed on the side opposite to the first outer mirror 212 with the optical axis 218 interposed therebetween. The second outer mirror 232 can be disposed at a position symmetric to the first outer mirror 212 with the optical axis 218 interposed therebetween. The second outer mirror 232 has a second outer reflecting surface 242 (or fourth reflecting surface) on which the X-rays 220 are obliquely incident. The second outer reflecting surface 242 reflects an X-ray beam 220c within a third angular range α3 from the first focal point F1 toward the second focal point F2. The second outer reflecting surface 242 may have a shape symmetric to the first outer reflecting surface 222 with the optical axis 218 interposed therebetween. In this case, the third angular range α3 is an angular range symmetric to the first angular range α1 with the optical axis 218 interposed therebetween. The second outer mirror 232 can be configured in the same manner as the outer mirror 12 according to the above-described first embodiment.

[0108] The second inner mirror 234 is disposed on the opposite side of the first inner mirror 214 across the optical axis 218. The second inner mirror 234 can be disposed at a position symmetric to the first inner mirror 214 across the optical axis 218. The second inner mirror 234 is disposed between the optical axis 218 and the second outer mirror 232. The second inner mirror 234 has a second inner reflection surface (or fifth reflection surface) 244 at which the X-ray 220 is obliquely incident, and a surface (or second back surface) 246 opposite to the second inner reflection surface 244. The second back surface 246 faces the second outer mirror 232. The second inner reflection surface 244 faces the first inner reflection surface 224. The second inner reflection surface 244 reflects the X-ray beam 220d within the fourth angular range α4 from the first focal point F1 toward the second focal point F2. The second inner reflection surface 244 may have a shape symmetric to the first inner reflection surface 224 across the optical axis 218. In this case, the fourth angular range α4 is an angular range symmetric to the second angular range α2 across the optical axis 218. The second inner mirror 234 can be configured in the same manner as the inner mirror 14 according to the above-described first embodiment.

[0109] According to this embodiment, by disposing an additional outer mirror and an additional inner mirror on the opposite sides across the optical axis, the total of the angular ranges α1, α2, α3, α4 of the X-rays 220 from the first focal point F1 that the X-ray mirror device 210 can focus (i.e., the numerical aperture) can be increased. Thereby, the spatial resolution can be improved, and for example, a spatial resolution of 10 nm or less or 5 nm or less can be achieved.

[0110] In a modified example, similar to the inner mirror 14A shown in FIG. 13, the thicknesses of the first inner mirror 214 and the second inner mirror 234 may be changed in a tapered shape.

[0111] In a modification, one or more first intermediate mirrors (or sixth mirrors) may be arranged between the first outer mirror 212 and the first inner mirror 214. Also, one or more second intermediate mirrors (or seventh mirrors) may be arranged between the second outer mirror 232 and the second inner mirror 234. One or more second intermediate mirrors may be arranged symmetrically with respect to one or more first intermediate mirrors across the optical axis 218. The first intermediate mirror and the second intermediate mirror can be configured in the same manner as the intermediate mirror 216 according to the tenth embodiment in FIG. 14. In the modification, similar to the inner mirror 14A shown in FIG. 13, the thicknesses of the first inner mirror 214 and the second inner mirror 234 may be tapered, and the thicknesses of the first intermediate mirror and the second intermediate mirror may be tapered.

[0112] (Embodiment 12) FIG. 16 is a perspective view schematically showing the configuration of an X-ray apparatus 60 according to the twelfth embodiment. The X-ray apparatus 60 is an example of an optical apparatus that uses X-rays, and is an X-ray microscope having a so-called imaging-type microscope configuration. The X-ray apparatus 60 includes an illumination optical system 62, a sample holding unit 64, an imaging optical system 66, and an X-ray detection unit 68. The X-ray apparatus 60 is configured to irradiate a sample 88 with X-rays 92 generated by an X-ray source 90 and detect an enlarged image of the X-rays 96 transmitted through the sample 88 by the X-ray detection unit 68.

[0113] The X-ray source 90 generates X-rays 92 for observing the sample 88. The type of the X-ray source 90 is not particularly limited, and an X-ray tube, a large-scale synchrotron radiation facility such as SPring-8, an X-ray free electron laser, or the like can be used. When a small device such as an X-ray tube is used as the X-ray source, the X-ray apparatus 60 may include the X-ray source 90. On the other hand, when a large device such as a synchrotron radiation facility is used as the X-ray source 90, the X-ray apparatus 60 may not include the X-ray source 90. The X-ray source 90 is configured to output hard X-rays of 2 keV or more, for example. The X-ray source 90 may generate monochromatic X-rays that are monochromatized to a specific wavelength, or may generate continuous X-rays (white X-rays) including various wavelength components.

[0114] The illumination optical system 62 is disposed between the X-ray source 90 and the sample holding unit 64. The illumination optical system 62 is configured to condense the X-rays 92 from the X-ray source 90 onto the sample holding unit 64. The illumination optical system 62 is constituted by a so-called KB (Kirkpatrick-Baez) mirror and includes a horizontal concave mirror 70 and a vertical concave mirror 72. The horizontal concave mirror 70 and the vertical concave mirror 72 are arranged such that the normal directions of their respective reflecting surfaces are orthogonal. The reflecting surfaces of the horizontal concave mirror 70 and the vertical concave mirror 72 are constituted by, for example, a concave curved surface of an ellipse having a focus at the position of the sample holding unit 64. The illumination optical system 62 may be constituted by four curved mirrors, similar to the imaging optical system 66 described later.

[0115] The sample holding unit 64 holds the sample 88 irradiated with the X-rays 94 emitted from the illumination optical system 62. The sample holding unit 64 holds the sample 88 to be observed on the optical path of the X-rays 94. The configuration of the sample holding unit 64 is not particularly limited, and any configuration for fixing the position of the sample 88 can be used according to the characteristics of the sample 88. The sample holding unit 64 includes, for example, a stage device for adjusting the position of the sample 88 with respect to the optical path of the X-rays 94.

[0116] The imaging optical system 66 is disposed between the sample holding unit 64 and the X-ray detection unit 68. The imaging optical system 66 is configured to form an image of the X-rays 96 from the sample holding unit 64 on the X-ray detection unit 68. The imaging optical system 66 is a so-called AKB (Advanced Kirkpatrick-Baez) mirror optical system and includes four curved mirrors 74, 76, 78, 80. The imaging optical system 66 is configured to achieve an image magnification of about 100 to 1,000 times, for example.

[0117] The imaging optical system 66 can be configured, for example, as a Wolter type 1 mirror that combines a hyperbolic concave mirror and an elliptical concave mirror. In this case, the first curved surface mirror 74 is a horizontal hyperbolic concave mirror and has a reflecting surface configured by a concave surface of a hyperbola that has a focus at the position of the sample holding part 64, for example. The second curved surface mirror 76 is a vertical hyperbolic concave mirror and has a reflecting surface configured by a concave surface of a hyperbola that has a focus at the position of the sample holding part 64, for example. The third curved surface mirror 78 is a horizontal elliptical concave mirror and has a reflecting surface configured by a concave surface of an ellipse that has a first focus at the position of the X-ray detection part 68 and a second focus shared with the first curved surface mirror 74. The fourth curved surface mirror 80 is a vertical elliptical concave mirror and has a reflecting surface configured by a concave surface of an ellipse that has a first focus at the position of the X-ray detection part 68 and a second focus shared with the second curved surface mirror 76.

[0118] In the example of FIG. 16, four curved surface mirrors 74 to 80 are arranged in the order of a horizontal hyperbolic concave mirror, a vertical hyperbolic concave mirror, a horizontal elliptical concave mirror, and a vertical elliptical concave mirror from the sample holding part 64 toward the X-ray detection part 68, but the arrangement order is not limited to this. For example, a horizontal elliptical concave mirror may be arranged next to the horizontal hyperbolic concave mirror, or a vertical elliptical concave mirror may be arranged next to the vertical hyperbolic concave mirror. Also, the imaging optical system 66 can be configured as a Wolter type 3 mirror that combines an elliptical concave mirror and a hyperbolic convex mirror. In this case, the first curved surface mirror 74 can be a horizontal elliptical concave mirror, the second curved surface mirror 76 can be a vertical elliptical concave mirror, the third curved surface mirror 78 can be a horizontal hyperbolic convex mirror, and the fourth curved surface mirror 80 can be a vertical hyperbolic convex mirror.

[0119] The X-ray detection unit 68 detects the X-rays 98 emitted from the imaging optical system 66. The X-ray detection unit 68 is, for example, an X-ray camera that detects a two-dimensional image of the X-rays 98. The configuration of the X-ray detection unit 68 is not particularly limited, but for example, a direct conversion type or indirect conversion type image sensor (CCD or CMOS sensor) can be used. The X-ray detection unit 68 may include an optical element such as a lens for enlarging the visible light image converted by the scintillator and an image sensor for imaging the enlarged visible light image in order to further enhance the resolution.

[0120] At least one of the illumination optical system 62 and the imaging optical system 66 can include the X-ray mirror devices 10, 10A, 110, or 210 according to the above-described embodiments or modified examples.

[0121] At least one of the horizontal concave mirror 70 and the vertical concave mirror 72 constituting the illumination optical system 62 may be constituted by the X-ray mirror device 10, 10A, 110, or 210. The X-ray mirror device 10, 10A, 110, or 210 may be applied only to the horizontal concave mirror 70, only to the vertical concave mirror 72, or to both the horizontal concave mirror 70 and the vertical concave mirror 72.

[0122] At least one of the four curved mirrors 74 to 80 constituting the imaging optical system 66 may be constituted by the X-ray mirror device 10, 10A, 110, or 210. The X-ray mirror device 10, 10A, 110, or 210 may be applied to any one, two, or three of the four curved mirrors 74 to 80, or to all of them. By using the X-ray mirror device 10, 10A, 110, or 210 in at least one of the illumination optical system 62 and the imaging optical system 66, the characteristics of the X-ray optical system can be improved and the spatial resolution can be improved.

[0123] The X-ray mirror devices 10, 10A, 110, or 210 according to the present disclosure are preferably applied to an imaging optical system 66 that requires a higher numerical aperture. In particular, it is preferable to apply the X-ray mirror devices 10, 10A, 110, or 210 to each of a horizontal curved mirror and a vertical curved mirror that are disposed near the sample holding unit 64 and serve as an objective lens of the imaging optical system 66. In the configuration of FIG. 16, it is preferable to apply to one or both of the first curved mirror 74 that is a horizontal hyperbolic concave mirror and the second curved mirror 76 that is a vertical hyperbolic concave mirror. This is because in order to increase the resolution of the imaging optical system 66, it is necessary to increase the numerical aperture of the imaging optical system 66. By applying the X-ray mirror devices 10, 10A, 110, or 210 to the curved mirror that serves as the objective lens of the X-ray optical system, the spatial resolution of the X-ray device 60 can be effectively improved.

[0124] Similar to the illumination optical system 62, the imaging optical system 66 may be configured by a KB mirror including a horizontal concave mirror and a vertical concave mirror. In this case, by using the X-ray mirror devices 10, 10A, 110, or 210 for at least one of the horizontal concave mirror and the vertical concave mirror, the characteristics of the imaging optical system 66 can be improved, and the spatial resolution of the X-ray device 60 can be improved.

[0125] The X-ray device 60 may further include an X-ray spectrometer (not shown) disposed between the X-ray source 90 and the illumination optical system 62. The X-ray spectrometer is configured to monochromatize the X-ray 92 from the X-ray source 90. The X-ray spectrometer may be a crystal spectrometer such as a two-crystal monochromator, or may be configured such that the X-ray wavelength is variable by changing the crystal angle. By making the X-ray wavelength variable, the X-ray device 60 can provide XAFS (X-ray Absorption Fine Structure) imaging. Since the X-ray device 60 is configured by an X-ray optical system with little chromatic aberration, it can provide a high-resolution (e.g., 10 nm or less or 5 nm or less) XAFS image simply by changing the X-ray wavelength.

[0126] The X-ray mirror devices 10, 10A, 110, or 210 according to the present disclosure can be applied to any X-ray device, and in particular, can be applied to X-ray optical systems such as a condenser optical system or an imaging optical system included in an X-ray device. As an example of an X-ray device, in addition to the imaging X-ray microscope illustrated in FIG. 16, a scanning X-ray microscope and an X-ray telescope can be mentioned.

[0127] The scanning X-ray microscope includes a condenser optical system that condenses X-rays onto a sample holding unit, and at least one of the X-ray mirrors constituting the condenser optical system may be the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure. In the case of a scanning X-ray microscope, the resolution is determined by the beam size of the X-rays condensed by the condenser optical system. By using the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure, the characteristics of the condenser optical system can be improved, and the resolution of the scanning X-ray microscope can be improved. As the condenser optical system of the scanning X-ray microscope, a horizontal concave mirror 70 and a vertical concave mirror 72 similar to the illumination optical system 62 in FIG. 16 can be used, and the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can be used for at least one of them. As the condenser optical system of the scanning X-ray microscope, an AKB mirror optical system including four curved mirrors can also be used, and the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can be used for at least one of the four curved mirrors.

[0128] The X-ray telescope includes an imaging optical system that forms an image of X-rays from a celestial object to be observed on an X-ray detector, and at least one of the X-ray mirrors constituting the imaging optical system may be the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure. As the imaging optical system of the X-ray telescope, for example, an AKB mirror optical system similar to the imaging optical system 66 in FIG. 16 can be used. When the sample 88 in FIG. 16 is regarded as a celestial object to be observed, a Wolter type 1 imaging optical system in which the first curved mirror 74 and the second curved mirror 76 are parabolic concave mirrors, and the third curved mirror 78 and the fourth curved mirror 80 are hyperbolic concave mirrors can be used. Alternatively, a Wolter type 3 imaging optical system in which the first curved mirror 74 and the second curved mirror 76 are parabolic convex mirrors, and the third curved mirror 78 and the fourth curved mirror 80 are elliptical concave mirrors can be used. When using the Wolter type 3, since it is easy to ensure the distance from the optical axis to the elliptical concave mirror, it becomes easy to arrange the inner mirror between the optical axis and the outer mirror. In these cases, the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can be used for at least one of the four curved mirrors.

[0129] The X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure may be used as a wavefront compensation optical element in any X-ray device. When used as a wavefront compensation optical element, the reflection surface, which is substantially flat, is slightly deformed, for example, by making it the shape opposite to the wavefront aberration of the obliquely incident X-rays, to compensate for the wavefront aberration of the incident X-rays. The X-rays whose wavefront aberration has been compensated by the X-ray mirror device 10, 10A, 110, or 210 may be further processed by X-ray optical elements such as lenses and mirrors, may be irradiated onto a sample held by a sample holding unit, or may be detected by an X-ray detector.

[0130] The X-ray mirror devices 10, 10A, 110, or 210 according to the present disclosure may be applied to a photolithography apparatus that uses X-rays. The photolithography apparatus includes, for example, an illumination optical system for irradiating X-rays from an X-ray source onto a pattern mask, and an imaging optical system for imaging the X-rays patterned by the pattern mask onto a sample such as a wafer. The X-ray mirror devices 10, 10A, 110, or 210 according to the present disclosure can be applied to at least one of the illumination optical system and the imaging optical system of the photolithography apparatus.

[0131] The deformable mirrors 30, 30A, 30B, 30C, 30D, or 30E according to the present disclosure can be used as a wavefront compensation optical element for compensating the wavefront aberration of a laser beam. For example, it can be used as a wavefront compensation optical element for an ultra-high intensity laser used in laser fusion.

[0132] (13th Embodiment) FIG. 17 is a diagram schematically showing the configuration of an optical apparatus 300 according to the 13th embodiment. The optical apparatus 300 includes a laser light source 302 and an irradiation optical system 304. The optical apparatus 300 is used to irradiate a fuel capsule 306 held by a sample holding unit 308 with laser light 332 provided from the laser light source 302 to cause nuclear fusion in the fuel capsule 306. The fuel capsule 306 contains, for example, deuterium and tritium as fuel. When deuterium and tritium undergo nuclear fusion, helium and high-speed neutrons (about 10.6 MeV) are generated, and power generation is performed using the thermal energy extracted from the high-speed neutrons.

[0133] The laser light source 302 is, for example, 1 TW (10 12 W) or more, or 1 PW (10 15W) It is configured to output a high-intensity laser beam having the above peak output. The output wavelength of the laser light source 302 is not particularly limited. For example, it is configured to output near-infrared light such as 1053 nm or 1064 nm, or harmonics of near-infrared light (second harmonic, third harmonic, or fourth harmonic). The laser light source 302 is a pulsed laser and outputs a laser beam 332 having a pulse width of 10 ns or less, 1 ns or less, 100 ps or less, or 10 ps or less. The pulse energy of the laser beam 332 is, for example, 100 J or more, 1 kJ or more, 10 kJ or more, 100 kJ or more, or 1 MJ or more. The beam diameter of the laser beam 332 provided from the laser light source 302 to the irradiation optical system 304 is, for example, 10 cm or more, 30 cm or more, 50 cm or more, 80 cm or more, or 100 cm or more.

[0134] The irradiation optical system 304 includes a first folding mirror 310, a second folding mirror 312, a steering mirror 314, and a condenser mirror 316. The laser beam 332 from the laser light source 302 is reflected by the first folding mirror 310 and the second folding mirror 312 and then enters the steering mirror 314. The steering mirror 314 condenses the laser beam toward an intermediate focus 318 located between the steering mirror 314 and the condenser mirror 316. The condenser mirror 316 reflects the laser beam from the intermediate focus 318 and condenses it onto the fuel capsule 306. The steering mirror 314 is, for example, a parabolic mirror, and the condenser mirror 316 is, for example, an elliptical mirror. The steering mirror 314 and the condenser mirror 316 are an example of a condensing optical element that condenses the laser beam 332. The condensing optical element is not limited to a reflection type and may be a transmission type optical element such as a lens.

[0135] The optical elements (the first folding mirror 310, the second folding mirror 312, the steering mirror 314, and the condenser mirror 316) included in the irradiation optical system 304 have a size corresponding to the beam diameter of the laser beam 332. The size of the optical elements included in the irradiation optical system 304 is equal to or larger than the beam diameter of the laser beam 332, for example, 20% or more larger than the beam diameter. The size of the optical elements included in the irradiation optical system 304 is, for example, 10 cm or more, 15 cm or more, 30 cm or more, 40 cm or more, 50 cm or more, 60 cm or more, 80 cm or more, or 100 cm or more.

[0136] The irradiation optical system 304 is disposed inside a housing 320 for shielding fast neutrons flying from the fuel capsule 306. The irradiation optical system 304 may include the housing 320. Inside the housing 320, a folding optical path for the laser beam 332 to pass through is provided. In the vicinity of the intermediate focus 318, a narrow path 328 having a narrower optical path width than other locations is formed. The narrow path 328 functions as a neutron filter for shielding fast neutrons. By forming the narrow path 328, it is possible to prevent the steering mirror 314, the second folding mirror 312, and the first folding mirror 310 located upstream of the narrow path 328 from being directly irradiated with fast neutrons.

[0137] On the other hand, it is difficult to prevent the condenser mirror 316 located downstream of the narrow path 328 from being directly irradiated with fast neutrons. Therefore, the surface of the condenser mirror 316 is likely to be damaged by the irradiation of fast neutrons, and the surface shape accuracy for accurately condensing the laser beam 334 onto the fuel capsule 306 cannot be maintained. In other words, the damage to the surface of the condenser mirror 316 causes the wavefront of the laser beam 334 to be disturbed, and the condensing accuracy of the laser beam 334 decreases. In order to compensate for such a disturbance of the wavefront of the laser beam 334, at least one of the first folding mirror 310 and the second folding mirror 312 can be used as a wavefront compensation optical element. That is, the shape-variable mirrors 30, 30A, 30B, 30C, 30D, 30E, or 30F according to the above-described embodiments can be used for at least one of the first folding mirror 310 and the second folding mirror 312.

[0138] The irradiation optical system 304 can further include a beam splitter 322 disposed between the second turning mirror 312 and the steering mirror 314, and a detector 324 that detects the light reflected by the beam splitter 322. The beam splitter 322 is arranged to guide the return light from the fuel capsule 306 to the detector 324. The detector 324 measures the damage to the surface of the condenser mirror 316 by detecting the light that has passed through the condenser mirror 316 and the steering mirror 314 from the fuel capsule 306. The measurement result of the detector 324 can be used for controlling the wavefront compensation in at least one of the first turning mirror 310 and the second turning mirror 312.

[0139] The irradiation optical system 304 includes a deformable mirror (at least one of the first turning mirror 310 and the second turning mirror 312) that reflects the laser light 332 provided from the laser light source 302, and a condenser mirror 316 that condenses the laser light reflected by the deformable mirror toward the fuel capsule 306 held by the sample holding unit 308. At least one of the first turning mirror 310 and the second turning mirror 312 can be configured in the same manner as the deformable mirrors 30, 30A, 30B, 30C, 30D, 30E, or 30F according to the above-described embodiment. By using a piezoelectric single crystal material such as LN or LT as the deformable mirror, the occurrence of hysteresis and drift can be suppressed, and the shape of the reflecting surface can be uniquely determined according to the applied voltage. Therefore, the disturbance of the wavefront of the laser light 334 irradiated on the fuel capsule 306 can be compensated with high precision, and the influence of the damage to the surface of the condenser mirror 316 can be mitigated. As a result, the maintenance period of the condenser mirror 316 can be extended, contributing to the realization of a laser fusion reactor capable of stable operation over a long period.

[0140] (14th Embodiment) FIG. 18 is a diagram schematically showing the configuration of a laser fusion reactor 400 according to the 14th embodiment. The laser fusion reactor 400 includes a laser light source 402, an irradiation optical system 404, a fuel supply device 408, a reaction vessel 410, a blanket 412, a containment vessel 414, a laser inlet 416, and a fuel inlet 418.

[0141] The laser light source 402 and the irradiation optical system 404 can be configured in the same manner as the laser light source 302 and the irradiation optical system 304 described above. The laser light 424 output from the irradiation optical system 404 is introduced into the internal space 420 of the reaction vessel 410 through the laser inlet 416. The laser light 424 is irradiated onto the fuel capsule 406 introduced into the internal space 420 of the reaction vessel 410. In the example shown in FIG. 18, the fuel capsule 306 is irradiated with the laser light 424 from four directions using four laser light sources 402 and irradiation optical systems 404, but the number of irradiations of the laser light 424 is not particularly limited and may be 3 or less, or 5 or more. The number of irradiations of the laser light 424 may be 10 or more, or 20 or more. As the laser light for irradiating the fuel capsule 306, a compression laser light for compressing the fuel and an ignition laser light for igniting the fuel may be combined.

[0142] The fuel supply device 408 introduces the fuel capsule 406 into the internal space 420 of the reaction vessel 410 through the fuel inlet 418. The reaction vessel 410 has an internal space 420 into which the fuel capsule 406 and the laser light 424 are introduced. A blanket 412 is provided inside the reaction vessel 410. The blanket 412 absorbs fast neutrons generated in the nuclear fusion reaction in the fuel capsule 406 and converts them into heat. The blanket 412 contains a material capable of fuel reproduction. The blanket 412 includes, for example, a solid material (e.g., lithium titanate) or a liquid material (e.g., lead titanate, lithium fluoride-beryllium) containing lithium (Li), and is configured to reproduce tritium by neutron capture. The containment vessel 414 is disposed outside the reaction vessel 410. A neutron shielding material 422 such as water is accommodated inside the containment vessel 414.

[0143] The heat generated in the blanket 412 is transferred to the fluid flowing inside the pipe 428 introduced into the reaction vessel 410 and sent to the steam generator 430. The fluid flowing inside the pipe 428 circulates by means of a pump (not shown). The steam generator 430 generates steam using the heat from the fluid flowing inside the pipe 428. The steam generated in the steam generator 430 is sent to the steam turbine 432 to drive the steam turbine 432. The generator 434 generates electricity using the driving force generated in the steam turbine 432.

[0144] As described above, the present disclosure has been described based on the embodiments. It is understood by those skilled in the art that the present disclosure is not limited to the above embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present disclosure.

Industrial Applicability

[0145] According to an aspect of the present disclosure, the numerical aperture of an optical system with less chromatic aberration can be improved.

Explanation of Signs

[0146] 10, 10A... X-ray mirror device, 12... outer mirror, 14, 14A... inner mirror, 18... optical axis, 20... X-ray, 22... outer reflecting surface, 24... inner reflecting surface, 26, 26A... back surface, 30, 30A, 30B, 30C, 30D, 30E, 30F... shape-variable mirror, 32, 32B... piezoelectric substrate, 33, 34... reflecting surface electrode, 36, 37... back surface electrode, 38... power supply, 40... reflecting surface, 42... back surface, 44, 44B... first piezoelectric layer, 46, 46B... second piezoelectric layer, 48... intermediate electrode, 60... X-ray microscope, 62... illumination optical system, 64... sample holding section, 66... imaging optical system, 68... X-ray detection section, 110... X-ray mirror device, 112... outer mirror, 114... inner mirror, 116... intermediate mirror, 120... X-ray, 122... outer reflecting surface, 124... inner reflecting surface, 126... back surface, 128... intermediate reflecting surface, 130... back surface, 210... X-ray mirror device, 212... first outer mirror, 214... first inner mirror, 218... optical axis, 220... X-ray, 222... first outer reflecting surface, 224... first inner reflecting surface, 226... first back surface, 232... second outer mirror, 234... second inner mirror, 242... second outer reflecting surface, 244... second inner reflecting surface.

Claims

1. A piezoelectric substrate having a reflecting surface on which light is incident and a surface opposite to the reflecting surface, a first electrode located on the reflecting surface, a second electrode located on the opposite surface, and a power source for applying a voltage between the first electrode and the second electrode, wherein at least one of the first electrode and the second electrode includes a plurality of electrodes, the power source is capable of applying different voltages to the plurality of electrodes, the piezoelectric substrate is composed of a single piezoelectric single crystal substrate in which a first piezoelectric layer having the reflecting surface and a second piezoelectric layer having the opposite surface are integrated, and the polarization direction of the second piezoelectric layer is opposite to that of the first piezoelectric layer, a mirror device.

2. The second electrode includes a plurality of electrodes arranged in a two-dimensional array on the opposite surface, The mirror device according to Claim 1.

3. Further comprising a dielectric multilayer mirror located on the first electrode, The mirror device according to Claim 1.

4. Further comprising a reflective film located on the reflecting surface, the first electrode is located at a position different from the reflective film on the reflecting surface, The mirror device according to Claim 1.

5. The first electrode includes a plurality of electrodes arranged around the reflective film, The mirror device according to Claim 4.

6. Preparing a piezoelectric substrate having a first surface and a second surface opposite to the first surface, the polarization direction being constant from the first surface to the second surface, and composed of a single piezoelectric single crystal substrate, heating the piezoelectric substrate to form a polarization inversion layer over the entire piezoelectric substrate such that the polarization direction on the first surface side and the polarization direction on the second surface side are opposite, forming a first electrode on the first surface, forming a second electrode on the second surface, wherein at least one of the first electrode and the second electrode includes a plurality of electrodes, a method for manufacturing a mirror device.

7. The piezoelectric substrate is made of lithium niobate, forming the polarization inversion layer includes heating the piezoelectric substrate at a temperature of 1100 °C or higher and 1150 °C or lower, The manufacturing method according to Claim 6.

8. The piezoelectric substrate is made of lithium tantalate, forming the polarization inversion layer includes immersing the piezoelectric substrate in an acid for proton exchange and heating the proton-exchanged piezoelectric substrate at a temperature of 550 °C or higher and 600 °C or lower, The manufacturing method according to Claim 6.

9. A laser light source that outputs laser light having a peak output of 1 TW or more, A deformable mirror that compensates for the wavefront of the laser light, A condensing optical element that condenses the laser light reflected by the deformable mirror, and comprising: The deformable mirror, An incident surface on which the laser light is incident, and a surface opposite to the incident surface, and a piezoelectric substrate made of a piezoelectric single crystal material, A first electrode located on the incident surface, A second electrode located on the opposite surface, A dielectric multilayer film mirror located on the first electrode and reflecting the laser light, An optical device comprising a power supply that applies a voltage between the first electrode and the second electrode.

10. An optical device comprising a laser light source that outputs laser light, a deformable mirror that compensates for the wavefront of the laser light, and a condensing optical element that condenses the laser light reflected by the deformable mirror, A reaction vessel having an internal space into which the laser light output from the optical device is introduced and containing a fuel in which nuclear fusion occurs by irradiation with the laser light, The deformable mirror, An incident surface on which the laser light is incident, and a surface opposite to the incident surface, and a piezoelectric substrate made of a piezoelectric single crystal material, A first electrode located on the incident surface, A second electrode located on the opposite surface, A dielectric multilayer film mirror located on the first electrode and reflecting the laser light, A laser fusion reactor comprising a power supply that applies a voltage between the first electrode and the second electrode.

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