A trapezoidal multilayer film laue lens

Abstract

The application discloses a trapezoidal multilayer film Laue lens, characterized in that the trapezoidal multilayer film Laue lens comprises a plurality of functional film layers which are arranged in a stack, one end of each of the functional film layers is used as an incident surface along an optical axis direction, and the other end is used as an exit surface; the exit surface of each of the functional film layers has the same inclination angle with the optical axis direction, the exit surfaces of the functional film layers constitute a slope as an exit surface of the trapezoidal multilayer film Laue lens, and each of the functional film layers is parallel to the optical axis direction; and the thickness of the functional film layers in at least a continuous partial layer interval changes linearly along a gradient of a direction perpendicular to the optical axis. Compared with a rectangular multilayer film Laue lens, the trapezoidal multilayer film Laue lens has a certain degree of improvement in diffraction efficiency and a great improvement in focusing resolution.

Description

Technical Field

[0001] This invention relates to the field of hard X-ray focusing optical elements, and specifically to a trapezoidal multilayer Laue lens. Background Technology

[0002] X-ray microscopy can be used to characterize nanoscale density, elemental composition, elemental valence states, strain, morphology, magnetism, atomic and electronic structure, and dynamics in complex materials. This technique is of great significance in research fields such as biology, medicine, materials science, physics, and chemistry. The focusing size of X-rays directly affects the characterization capability of X-ray microscopes. Currently, multilayer Laue lenses (MLLs) are considered the most effective optical elements for focusing X-rays smaller than 10 nanometers.

[0003] Multilayer Laue lenses are typically rectangular in structure, meaning the incident and exit surfaces are parallel. This structure is advantageous for the fabrication of multilayer Laue lens slices, but the rectangular lens structure leads to uneven efficiency at the exit surface, thus reducing the effective aperture. Summary of the Invention

[0004] The purpose of this application is to provide a trapezoidal multilayer Laue lens, at least for improving the focusing performance of a multilayer Laue lens. Through practical research, this invention has found that if the exit surface is given a certain tilt angle instead of being parallel to the incident surface, the multilayer Laue lens will have superior focusing performance. Based on this, the trapezoidal multilayer Laue lens provided by this invention comprises multiple functional layers stacked together. The exit surface of each functional layer is tilted relative to the transmission axis of the multilayer Laue lens, and each functional layer is parallel to the transmission axis (i.e., the X-axis), with its exit surface having the same tilt angle as the optical axis X. The exit surfaces of each functional layer form an inclined surface as the exit surface of the trapezoidal multilayer Laue lens. Each functional layer includes a stacked absorption layer and a spacer layer, with the absorption layer and spacer layer of adjacent functional layers alternating (i.e., the absorption layer of the i-th functional layer is opposite to the spacer layer of the (i+1)-th functional layer). The thickness of the functional layers within at least a portion of the layer range varies linearly along the gradient perpendicular to the optical axis.

[0005] The functional film layer provides focusing; the combination of the absorption layer and the spacer layer provides a certain difference in optical constants, so that the interface between the absorption layer and the spacer layer reflects light incident along the optical axis.

[0006] As an alternative implementation, the absorber layer and the spacer layer in the same functional membrane layer have the same thickness.

[0007] As an implementation method, the absorber layer is made of at least one of WSi2 and Nb, and the spacer layer is made of at least one of Si and Al.

[0008] As an implementation method, the gradients of each of the functional membrane layers within at least a certain number of layers are obtained in the following manner:

[0009]

[0010] Where n is the number of functional layers in the multilayer Laue lens from thickest to thinnest, the nth functional layer is the functional layer within the at least continuous interval of the number of layers, and r n Let λ be the positional radius of the nth functional layer (i.e., the distance from the bottom of the nth functional layer to the bottom of the bottommost 1st functional layer), λ be the operating wavelength of the multilayer Laue lens, f be the focal length of the multilayer Laue lens, and D be the position radius of the nth functional layer (i.e., the distance from the bottom of the nth functional layer to the bottom of the bottommost 1st functional layer), f be the focal length of the multilayer Laue lens, and n The thickness of the nth functional film layer is such that the thickness of the functional layer decreases along the direction perpendicular to the optical axis and from thickest to thinnest, and the process changes polynomially.

[0011] As an implementation method, the maximum number N of the functional films of the multilayer Laue lens is determined according to the following relationship;

[0012] D N =2*d rout ;

[0013] Among them, D N d is the thickness of the Nth functional film layer; rout d represents the thickness of the outermost absorber layer or the spacer layer. rout Set the desired focus resolution yourself (required resolution = d). rout ), D is obtained from drout N Then, it's equivalent to using a table lookup method (D) N The value in D n (Look up the corresponding value in the data) to obtain the value of N.

[0014] Based on the wavelength λ of the incident light, the focal length f of the -1st order diffracted light from the lens, and the number of film layers, the curve η-1(Z) of the -1st order diffraction efficiency as a function of the cross-sectional depth Z is calculated, thus obtaining the optimal cross-sectional depth Z of the rectangular multilayer Laue lens. opt .

[0015] Select Z opt Using the center height as the cross-sectional depth and the center height as the origin, the slope of the exit surface is optimized to obtain the highest diffraction efficiency and focusing resolution. The tilt angle corresponding to the highest diffraction efficiency and focusing resolution is taken as the tilt angle between the exit surface of the functional film and the optical axis.

[0016] The incident surfaces of each functional film layer are aligned to form the incident surface of the trapezoidal multilayer Laue lens, and the exit surfaces of each functional film layer form an inclined plane to form the exit surface of the trapezoidal multilayer Laue lens.

[0017] The advantages of this invention are as follows:

[0018] This invention changes the shape of the multilayer Laue lens from the default rectangle to a trapezoid. The optimal penetration depth of the rectangular multilayer Laue lens is selected as the center thickness, and the exit surface slope is optimized with the center height vertex as the origin. This change in shape leads to a change in focusing performance; the penetration depth varies from the top film to the bottom film, corresponding to the optimal penetration depth for each layer, thereby increasing the overall focusing performance and actual focusing resolution of the original rectangular lens.

[0019] By comparison, the trapezoidal multilayer Laue lens has a diffraction efficiency of 10% and a focusing resolution of 10.66 nm, while the rectangular multilayer Laue lens has a diffraction efficiency of 8.9% and a focusing resolution of 13.78 nm. Therefore, it not only has a certain degree of improvement in diffraction efficiency, but also a significant improvement in focusing resolution. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a trapezoidal multilayer Laue lens provided in an embodiment of the present invention.

[0021] Figure 2 A comparison diagram of the intensity distribution near the focal point when focusing is achieved between a gradient multilayer Laue lens (the functional film layer of the present invention) and a rectangular multilayer Laue lens.

[0022] (a) First shape, (b) Second shape, (c) Third shape, (d) Fourth shape, (e) Fifth shape, (f) Sixth shape, (g) Seventh shape.

[0023] Figure 3 This is a 1D focusing comparison image of a gradient multilayer Laue lens (the functional film layer of the present invention) and a rectangular multilayer Laue lens. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Assuming the incident light energy E = 20 keV, the required focusing resolution is 8 nm, and the selected focal length is 4 mm, the total film thickness should be 41.2 μm. Based on the coating capability and resolution requirements, the outermost layer thickness is selected as 3 nm. According to the calculation, the total number of film layers is 6865.

[0026] The initial structure of the multilayer Laue lens was calculated based on lens structure formulas 1 and 2, including 6865 functional film layers stacked together. One end of each functional film layer along the optical axis serves as the incident surface, and the other end serves as the exit surface. The exit surface of each functional film layer has the same tilt angle as the optical axis, and each functional film layer is parallel to the optical axis. The thickness of the functional film layers within at least a continuous range of layers varies linearly along the gradient perpendicular to the optical axis.

[0027] Each functional film layer includes an absorption layer and a spacer layer stacked together. The interface between the absorption layer and the spacer layer provides reflection for light incident along the optical axis. The absorption layer and spacer layer of adjacent functional film layers are alternately arranged, and the absorption layer and spacer layer in the same functional film layer have the same thickness.

[0028] Using the Takagi-Taupin theory, the curve η-1(z) of the negative 1st order diffraction efficiency as a function of depth z was calculated.

[0029] The optimal depth Z with the highest efficiency is selected based on the diffraction curve η-1(z). opt =5.60μm.

[0030] Based on the optimal cross-sectional depth Z opt We selected 5.6 μm as the thickness of the multilayer Laue lens height center, and began to optimize the exit surface slope based on the overall diffraction efficiency and focusing resolution. The optimization range was -45 degrees to 45 degrees, and the optimization step size was 2.5 degrees.

[0031] During the optimization process, the electric field distribution on the outgoing surface needs to be calculated. The light intensity distribution on the image surface is obtained by using Kirchhoff-Fresnel diffraction integral. The final optimization result is that the focusing resolution of the trapezoidal multilayer Laue lens is 8nm, which is a significant improvement compared to the rectangular 13nm. The diffraction efficiency of the trapezoidal multilayer Laue lens is 10%, which is also a certain improvement compared to the 8.9% of the rectangular multilayer Laue lens.

[0032] Although specific embodiments of the invention have been disclosed for illustrative purposes to aid in understanding and implementing the invention, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the content disclosed in the preferred embodiments, and the scope of protection claimed by the invention is defined by the claims.

Claims

1. A trapezoidal multilayer Laue lens, characterized in that, It includes multiple functional film layers stacked together, with one end of each functional film layer serving as an incident surface and the other end serving as an exit surface along the optical axis; the exit surface of each functional film layer has the same tilt angle as the optical axis, and each functional film layer is parallel to the optical axis; The thickness of the functional film layer within at least a continuous range of layers varies linearly along the gradient direction perpendicular to the optical axis; wherein, according to the operating wavelength of the trapezoidal multilayer Laue lens... The focal length of the first-order diffracted light from the lens and the total number N of the functional films are calculated. The first-order diffraction efficiency varies with the cross-sectional depth. Z The changing curve η-1 ( Z To obtain the optimal cross-sectional depth of a rectangular multilayer Laue lens. Z opt Then select Z opt The center height is the cross-sectional depth. Taking the center height as the origin, the slope of the exit surface is optimized to obtain the tilt angle corresponding to the highest diffraction efficiency and focusing resolution. This tilt angle is taken as the tilt angle between the exit surface of the functional film and the optical axis.

2. The trapezoidal multilayer Laue lens according to claim 1, characterized in that, Each of the functional film layers includes an absorption layer and a spacer layer stacked together, and the interface between the absorption layer and the spacer layer provides a reflective effect for light incident along the optical axis; the absorption layer and spacer layer of adjacent functional film layers are alternately arranged.

3. The trapezoidal multilayer Laue lens according to claim 2, characterized in that, The absorber layer and the spacer layer in the same functional membrane layer have the same thickness.

4. The trapezoidal multilayer Laue lens according to claim 2 or 3, characterized in that, The absorber layer is made of at least one of WSi2 and Nb, and the spacer layer is made of at least one of Si and Al.

5. The trapezoidal multilayer Laue lens according to claim 1, 2, or 3, characterized in that, Let the nth functional film layer be the functional film layer within the at least continuous interval of the number of layers, and let the thickness of the nth functional film layer be... ; For the first The distance from the bottom of the first functional membrane layer to the bottom of the second functional membrane layer. The focal length is the trapezoidal multilayer Laue lens.

6. The trapezoidal multilayer Laue lens according to claim 5, characterized in that, 。 7. The trapezoidal multilayer Laue lens according to claim 1, characterized in that, according to Determine the total film thickness of the trapezoidal multilayer Laue lens Then according to Determine the total number N of functional membrane layers; among which, The thickness of the outermost absorption layer or spacer layer is set according to the target focusing resolution.

8. The trapezoidal multilayer Laue lens according to claim 1, characterized in that, The incident surfaces of each functional film layer are aligned to form the incident surface of the trapezoidal multilayer Laue lens, and the exit surfaces of each functional film layer form an inclined plane to form the exit surface of the trapezoidal multilayer Laue lens.

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