Preparation method of zone plate, zone plate and optical lens

Abstract

The present disclosure provides a method for preparing a zone plate, a zone plate, and an optical lens. The method includes determining a preset radius of each annular zone at a preset position based on a compensation phase difference and an optical path formula, wherein the compensation phase difference is determined based on a preset phase, a wavelength of light, and the optical path corresponding to the annular zone; the compensation phase difference is used to ensure that the optical path lengths of light passing through the same annular zone to reach an imaging point are equal, while the optical path length difference of light passing through different annular zones to reach the imaging point is an integer multiple of the wavelength of light, and the optical path formula characterizes the relationship between the radius parameter of each annular zone and the optical path length; determining a preset thickness of each annular zone at a preset position based on the complex refractive index of the zone plate and the compensation phase difference; and preparing an annular zone of a preset radius and preset thickness at the preset position of the zone plate for each annular zone, wherein the preset thickness ensures that the phase of light passing through all positions of the zone plate is synchronized at the imaging point.

Description

Technical Field

[0001] The present disclosure relates to the field of X-ray technology, and more specifically, to a method for preparing a high-efficiency high-order diffraction zone plate, a zone plate, and an optical lens. Background Art

[0002] Traditional zone plates are specialized variable-pitch gratings composed of alternating concentric light and dark zones with radially increasing line density. The resolution of a zone plate is determined by the width of the outermost zone. Resolution is a crucial imaging metric. In full-field X-ray transmission microscopy, system resolution is limited only by the width of the zone plate's outermost zone and the diffraction order.

[0003] However, the maximum efficiency of zone plates for high-order diffraction imaging decreases as one-half the square of the diffraction order. Even second-order diffraction imaging is only one-quarter as efficient as first-order diffraction. To achieve high-performance imaging, conventional designs based on first-order zone plate diffraction cannot meet the requirements for efficient high-order diffraction imaging. Summary of the Invention

[0004] In view of this, the embodiments of the present disclosure provide a method for preparing a high-efficiency high-order diffraction zone plate, a zone plate, and an optical lens.

[0005] One aspect of an embodiment of the present disclosure provides a method for preparing a zone plate, wherein the zone plate includes a plurality of adjacent annular zones. The method includes:

[0006] The preset radius of each of the annular zones at a preset position is determined based on a compensating phase difference and an optical path formula, wherein the compensating phase difference is determined based on a preset phase, a wavelength of light, and an optical path corresponding to the annular zone; the compensating phase difference is used to ensure that the optical path lengths of light reaching an imaging point after passing through the same annular zone are the same, and that the optical path length differences after passing through different annular zones are integer multiples of the wavelength of light; and the optical path length formula characterizes the relationship between the radius parameter of each of the annular zones and the optical path length;

[0007] Determining a preset thickness of each of the annular zones at the preset position according to the complex refractive index of the zone plate and the compensating phase difference;

[0008] For each of the annular zones, an annular zone with the preset radius and the preset thickness is prepared at the preset position of the zone plate, wherein the preset thickness enables the light passing through all positions of the zone plate to be phase-synchronized at the imaging point.

[0009] According to an embodiment of the present disclosure, the above-mentioned optical path formula is determined based on the imaging formula of the above-mentioned wave zone plate. The parameters of the above-mentioned imaging formula include the m-order focal length of the wave zone plate, the object distance and the image distance. The above-mentioned object distance represents the distance between the above-mentioned wave zone plate and the light-emitting point, and the above-mentioned image distance represents the distance between the above-mentioned wave zone plate and the imaging point.

[0010] According to an embodiment of the present disclosure, the optical path formula is determined based on the imaging formula of the zone plate, including:

[0011] Determine the first-order focal length of the zone plate, the object distance, and the image distance according to the imaging formula;

[0012] The optical path formula is determined according to the m-th order focal length of the zone plate, the object distance, and the image distance.

[0013] According to an embodiment of the present disclosure, the above imaging formula is as follows:

[0014]

[0015] Where f1 represents the first-order focal length of the zone plate, p represents the object distance, and q represents the image distance;

[0016] The above optical path length formula is as follows:

[0017]

[0018] Wherein, LP represents the optical path of the zone plate during m-order imaging, A represents the luminous point, B represents the imaging point, C represents the intersection of the light emitted by the luminous point and the annular zone during imaging, and r represents the radius parameter of the annular zone.

[0019] The above-mentioned compensation phase difference φ is as follows:

[0020]

[0021] Wherein, l represents any positive integer, φ0 represents the preset phase, φ0∈(0, 2π], λ represents the optical wavelength, and mod(LP, λ) is the modulus of LP with respect to λ.

[0022] According to an embodiment of the present disclosure, the method of determining the preset radius of each of the annular zones at a preset position based on the compensation phase difference and the optical path formula includes:

[0023] Determining the preset position corresponding to the annular zone according to the compensated phase difference and the optical path formula;

[0024] According to the above preset position, the preset radius of the above annular zone is determined.

[0025] According to an embodiment of the present disclosure, the step of determining the preset thickness of each of the annular zones at the preset position based on the complex refractive index of the zone plate and the compensating phase difference includes:

[0026] determining a reduction in the real part of the refractive index of the zone plate according to the complex refractive index of the zone plate;

[0027] The preset thickness of the annular zone is determined according to the reduction in the real part of the refractive index and the compensating phase difference.

[0028] According to an embodiment of the present disclosure, the above-mentioned preset positions are as follows:

[0029]

[0030] Where f1 represents the first-order focal length of the zone plate, r represents the radius parameter of the zone, and kλ represents the integer multiple of the wavelength.

[0031] Preset radius of the ring The calculation is as follows:

[0032]

[0033] The calculation of the above preset thickness t is as follows:

[0034]

[0035] n=(1-δ)+iβ

[0036] Where n represents the complex refractive index of the zone plate, (1-δ) represents the real part of the complex refractive index, δ represents the reduction in the real part of the refractive index, iβ represents the imaginary part of the complex refractive index, i represents the imaginary unit, and β represents the parameter related to the absorption coefficient of the zone plate material to light.

[0037] Another aspect of the embodiments of the present disclosure provides a high-order diffraction zone plate, comprising:

[0038] A plurality of adjacent annular zones, wherein the optical path length of light emitted from the light-emitting point from the same annular zone to the imaging point is the same, and the optical path length difference from light emitted from the light-emitting point to the imaging point from light emitted from the same annular zone to the imaging point is an integer multiple of the wavelength of the light;

[0039] The preset radius of the annular zone is determined according to the compensation phase difference and optical path formula, and the compensation phase difference is determined according to the preset phase, the wavelength of light and the optical path corresponding to the annular zone;

[0040] The preset thickness of the annular zone is determined according to the complex refractive index of the zone plate and the compensating phase difference.

[0041] Another aspect of the present disclosure provides an optical lens, comprising:

[0042] A zone plate prepared according to the preparation method described above;

[0043] Or a zone plate as described above.

[0044] According to an embodiment of the present disclosure, the optical lens includes a Kinoform lens.

[0045] According to an embodiment of the present disclosure, in the process of preparing the wave zone plate, the preset radius and preset thickness of adjacent ring zones are compensated by compensating the phase difference, so that the optical path difference between the two adjacent ring zones is an integer multiple of the wavelength of light, so that the X-rays from the two adjacent ring zones reaching the imaging point will not produce phase cancellation, thereby improving the diffraction efficiency during high-order diffraction imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0047] Figure 1 Schematically shows a structural diagram of a phase-type zone plate according to an embodiment of the present disclosure;

[0048] Figure 2 The following schematically shows a flow chart of a method for preparing a zone plate according to an embodiment of the present disclosure;

[0049] Figure 3 The structure of the zone plate according to the embodiment of the present disclosure is schematically shown. Figure 1 ;

[0050] Figure 4 The structure of the zone plate according to the embodiment of the present disclosure is schematically shown. Figure 2 ;

[0051] Figure 5 The optical principle diagram of a zone plate according to an embodiment of the present disclosure is schematically shown;

[0052] Figure 6 Schematically shows the relationship between the imaging energy of a zone plate and the preset thickness according to an embodiment of the present disclosure;

[0053] Figure 7 A schematic diagram schematically illustrates an outline of a zone plate according to an embodiment of the present disclosure; and

[0054] Figure 8 The figure schematically shows the outline of a zone plate according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0055] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0056] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0057] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0058] When expressions such as "at least one of A, B and C, etc." are used, they should generally be interpreted in accordance with the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0059] Figure 1 The structural diagram of a phase-type zone plate according to an embodiment of the present disclosure is schematically shown.

[0060] In the optimization design of zone plates, only the first-order diffraction efficiency is typically considered. For example, a phase-type zone plate replaces the light-blocking ring of a conventional 1:1 duty cycle amplitude-type zone plate with a π phase shift, thereby increasing the diffraction efficiency by a factor of four. Furthermore, the concept of positive and negative phase shifts can be used to further improve the first-order diffraction efficiency of a zone plate.

[0061] like Figure 1 The widths of the n-1th and nth adjacent ring zones of the phase zone plate are w n-1 and w n ,in, Figure 1 Different grayscales represent differently modulated ring zones. The phase-type zone plate has a duty cycle of 1:1, the planar area of ​​each ring zone is equal, and the phase modulation is fixed. However, the optical field differences at different radial positions of the phase-type zone plate vary, so light passing through different positions of the same ring zone is not synchronized. Even if adjacent ring zones are phase-modulated, this only synchronizes their average phase, resulting in low diffraction efficiency.

[0062] Current research on the high-order diffraction efficiency of zone plates is based on amplitude-type zone plates. Theoretically, a zone plate with a duty ratio of 1:1 has the highest odd-order diffraction efficiency, while the even-order diffraction efficiency is 0. Only zone plates with a duty ratio other than 1:1 have even-order diffraction efficiency. For example, for second-order diffraction, the highest diffraction efficiency is achieved when the zone plate has a duty ratio of 1:3 or 3:1.

[0063] In order to obtain efficient high-order diffraction imaging, the embodiments of the present disclosure provide a method for preparing an efficient high-order diffraction zone plate, a zone plate, and an optical lens. The method includes determining a preset radius of each ring zone at a preset position based on a compensation phase difference and an optical path formula, wherein the compensation phase difference is determined based on a preset phase, a wavelength of light, and an optical path corresponding to the ring zone; the compensation phase difference is used to ensure that the optical path of light passing through the same ring zone to reach the imaging point is the same, and the optical path difference of light passing through different ring zones to reach the imaging point is an integer multiple of the wavelength of the light, and the optical path formula characterizes the relationship between the radius parameter of each ring zone and the optical path; determining a preset thickness of each ring zone at a preset position based on the complex refractive index of the zone plate and the compensation phase difference; for each ring zone, a ring zone of a preset radius and a preset thickness is prepared at the preset position of the zone plate, wherein the preset thickness ensures that the phase of light passing through all positions of the zone plate is synchronized at the imaging point.

[0064] Figure 2 The flowchart of the method for preparing a zone plate according to an embodiment of the present disclosure is schematically shown. Figure 3 The structure of the zone plate according to the embodiment of the present disclosure is schematically shown. Figure 1 . Figure 4 The structure of the zone plate according to the embodiment of the present disclosure is schematically shown. Figure 2 .

[0065] like Figure 2 As shown, an embodiment of the present disclosure provides a method for preparing a zone plate, where the zone plate includes a plurality of adjacent annular zones. The method includes operations S201 to S203.

[0066] In operation S201, the preset radius of each annular band at a preset position is determined according to the compensation phase difference and the optical path formula, where the compensation phase difference is determined according to the preset phase, the wavelength of light and the optical path corresponding to the annular band; the compensation phase difference is used to ensure that the optical path of light reaching the imaging point through the same annular band is the same, while the optical path difference reaching the imaging point through different annular bands is an integer multiple of the wavelength of light, and the optical path formula characterizes the relationship between the radius parameter of each annular band and the optical path.

[0067] In operation S202 , a preset thickness of each annular zone at a preset position is determined according to the complex refractive index and the compensated phase difference of the zone plate.

[0068] In operation S203 , for each annular zone, an annular zone with a preset radius and a preset thickness is prepared at a preset position of the zone plate, wherein the preset thickness enables the phase of light passing through all positions of the zone plate to be synchronized at the imaging point.

[0069] According to an embodiment of the present disclosure, the preset position may represent a connection between two adjacent annular zones. The purpose of the preset position is to reduce the processing thickness of the zone plate to achieve lightweighting of the zone plate.

[0070] According to an embodiment of the present disclosure, the complex refractive index is the most important optical constant of the medium, wherein the medium may be each annular zone of a zone plate.

[0071] According to the embodiments of the present disclosure, when preparing the wave zone plate, it is necessary to design the preset radius and preset thickness of each annular zone. When determining the preset radius, the absorption of X-rays by the wave zone plate material is not taken into account. In order to maximize the high-order diffraction efficiency of the wave zone plate, it is necessary to ensure that the optical path of the X-ray emitted from the light emitting point through the entire area of ​​the wave zone plate when reaching the imaging point is consistent or has a difference of an integer multiple of the wavelength, that is, phase synchronization. The phase difference can be compensated for for processing, thereby determining the preset radius of each annular zone.

[0072] According to the embodiment of the present disclosure, when determining the preset thickness of each annular zone, it is also necessary to consider the change of the material with the radial direction. In this process, the preset thickness can be calculated using the complex refractive index and the compensation phase difference of the wave zone plate, thereby determining the thickness of each annular zone. After determining the preset radius and preset thickness, the corresponding annular zone is prepared at the preset position, thereby completing the following steps: Figure 3 and Figure 4 Preparation of the zone plate shown.

[0073] It should be noted that in Figure 3 and Figure 4 Different grayscales represent different thicknesses of the annulus, where Figure 3 The gray scale on the middle right side indicates the different thicknesses corresponding to different gray levels. The darker the color, the thinner the annulus. The thickness increases from the inside to the outside within the same annulus, and the minimum and maximum thicknesses of different annulus zones are the same. Figure 4 The thickness profile diagram in the figure discloses the change of thickness from the center position of the zone plate to the outside direction, wherein the preset position of the present disclosure can be Figure 4 The thickness change discontinuity in the thickness profile, such as Figure 4 The "point" position in the .

[0074] According to an embodiment of the present disclosure, during the preparation of a zone plate, the preset radius and preset thickness of adjacent zones are compensated by compensating for the phase difference, so that the optical path difference between two adjacent zones is an integer multiple of the wavelength of the light, so that the X-rays from the two adjacent zones to the imaging point will not produce phase cancellation, thereby improving the diffraction efficiency during high-order diffraction imaging. The above method of determining the preset thickness and preset radius of each zone of the zone plate ensures that the phase of all light from the light-emitting (or object plane) point through the zone plate to the focusing (or imaging) point is synchronized, thereby achieving coherent phase expansion.

[0075] According to an embodiment of the present disclosure, the optical path formula is determined based on the imaging formula of the wave zone plate. The parameters of the imaging formula may include the m-order focal length of the wave zone plate, the object distance and the image distance. The object distance represents the distance between the wave zone plate and the light-emitting point, and the image distance represents the distance between the wave zone plate and the imaging point.

[0076] According to an embodiment of the present disclosure, the optical path formula is determined based on the imaging formula of the zone plate, and may include the following operations.

[0077] The m-th order focal length, object distance, and image distance of the zone plate are determined based on the imaging formula. The optical path length formula is determined based on the m-th order focal length, object distance, and image distance of the zone plate.

[0078] According to an embodiment of the present disclosure, the object distance may represent the straight-line distance between the light-emitting point or the object surface point and the plane where the annulus is located. The image distance may represent the straight-line distance between the imaging point and the plane where the annulus is located.

[0079] According to an embodiment of the present disclosure, the parameters included in the imaging formula include the m-th order focal length of the zone plate, the object distance and the image distance. The imaging formula between the object distance, the annular zone and the image distance can be determined based on the above parameters.

[0080] Figure 5 The optical principle diagram of one ring zone of the zone plate according to an embodiment of the present disclosure is schematically shown.

[0081] Reference Figure 5 , the imaging formula is shown in formula (1):

[0082]

[0083] Where f1 represents the first-order focal length of the zone plate, p represents the object distance, and q represents the image distance.

[0084] The optical path formula is shown in formula (2):

[0085]

[0086] Among them, LP represents the optical path when the wave plate is imaged in the mth order, A represents the light-emitting point, B represents the imaging point, C represents the intersection of the light emitted by the light-emitting point and the annular zone during imaging, and r represents the radius parameter of the annular zone.

[0087] The compensation phase difference φ is shown in formula (3):

[0088]

[0089] Wherein, l represents any positive integer, φ0 represents the preset phase, φ0∈(0, 2π], λ represents the optical wavelength, and mod(LP, λ) is the modulus of LP with respect to λ.

[0090] According to the embodiment of the present disclosure, p+q is the optical path of light emitted from the light-emitting point directly reaching the imaging point, It is the difference between the optical path length of the light passing through the annular zone to reach the imaging point and the optical path length of the light directly reaching the imaging point, wherein the compensation phase difference φ is used to compensate for the above difference.

[0091] According to an embodiment of the present disclosure, determining the preset radius of each annular zone at a preset position according to the compensation phase difference and the optical path formula may include the following operations:

[0092] The preset position corresponding to the annular zone is determined based on the compensation phase difference and the optical path formula, and the preset radius of the annular zone is determined based on the preset position.

[0093] According to the embodiments of the present disclosure, considering the thickness of the zone plate during processing, combined with the compensation phase difference and optical path formula, it can be determined that the surface of the zone plate at the preset position of the annular zone is discontinuous, that is, the surface is uneven.

[0094] According to an embodiment of the present disclosure, after the preset position is determined, the radius of the annular zone can be determined according to the preset position.

[0095] According to an embodiment of the present disclosure, determining the preset thickness of each annular zone at a preset position based on the complex refractive index and the compensated phase difference of the zone plate may include the following operations:

[0096] The refractive index of the zone plate is determined based on the complex refractive index of the zone plate, and the preset thickness of the ring zone is determined based on the refractive index and the compensation phase difference.

[0097] According to an embodiment of the present disclosure, the complex refractive index is a complex number, the real part of the refractive index determines the propagation speed of the light wave in the absorptive medium, and the imaginary part determines the attenuation (absorption of light energy) of the light wave when propagating in the absorptive medium, which is a parameter quantity related to the absorption coefficient.

[0098] According to the embodiments of the present disclosure, the preset thickness of the zone can be determined by combining the compensation phase difference and the complex refractive index of the zone plate. When the preset radius and preset thickness of each zone are determined, the zone plate can be manufactured according to the preset radius and preset thickness.

[0099] According to an embodiment of the present disclosure, the preset position is as shown in formula (4):

[0100]

[0101] Where f1 represents the first-order focal length of the zone plate, r represents the radius parameter of the zone, and kλ represents the integer multiple of the wavelength.

[0102] Preset radius of the ring The calculation of is shown in formula (5):

[0103]

[0104] According to an embodiment of the present disclosure, when the order m=1, It can be seen that the ring zone of the preset radius determined by the present disclosure spans two ring zones of the conventional wave zone plate. When the order m=2, The preset radius of the zone determined by the present disclosure spans one zone of the conventional zone plate. When the order m=3, The preset radius of the zone determined in this disclosure spans two-thirds of the zone of a conventional zone plate, and similar designs can be obtained in a higher order. Without considering the concept of higher order, directly setting f = f1 / m, the above formula can be changed to

[0105] The calculation of the preset thickness t is shown in formulas (6) and (7):

[0106]

[0107] n=(1-δ)+iβ (7)

[0108] Wherein, n represents the complex refractive index of the zone plate, (1-δ) represents the real part of the complex refractive index, iβ represents the imaginary part of the complex refractive index, i represents the imaginary unit, and β represents the parameter related to the absorption coefficient of the zone plate material to light.

[0109] It should be noted that the phase modulation range within a ring band is 0 to 2π, so the maximum thickness within a ring band is

[0110] Figure 6 The figure schematically shows the relationship between the imaging energy of one zone of the zone plate and the preset thickness according to the embodiment of the present disclosure.

[0111] In an illustrative embodiment, taking gold as an example, Figure 6 The maximum thickness is shown to be And from the energy variation curve of imaging energy from 0.2KeV to 10KeV, it can be seen that the thickness of gold varies within a ring band in the micrometer range.

[0112] According to formula (3), formula (5) and formula (6), the thickness of each annular zone filling material as a function of radial position can be calculated as shown in formula (8).

[0113]

[0114] Assume the incident light amplitude is A0, consider the area relationship and use variable substitution x=r 2 According to the thin grating approximation formula, the amplitude of light passing through a ring zone can be calculated. The amplitude of the light A u As shown in formula (9), its diffraction efficiency η is shown in formula (10).

[0115]

[0116]

[0117] From the above formula, it can be determined that the diffraction efficiency of each ring zone is the same.

[0118] According to the embodiment of the present disclosure, based on the calculation method of the diffraction efficiency of formula (9), the zone plate material can be selected according to actual needs. It is best to select a material with a larger δ / β ratio to obtain a higher diffraction efficiency.

[0119] According to the embodiments of the present disclosure, the above method for determining the preset thickness and preset radius of each ring zone of the wave zone plate is suitable for the design of wave zone plates of any order. Formulas (5)(8)(10) all take the diffraction order m into consideration, and corresponding high-efficiency diffraction wave zone plates can be designed according to different orders.

[0120] Figure 7 The figure schematically shows the outline of a zone plate according to an embodiment of the present disclosure. Figure 8 The figure schematically shows the outline of a zone plate according to another embodiment of the present disclosure.

[0121] In an exemplary embodiment, taking the second-order diffraction imaging at an imaging energy of 2 KeV as an example, the real part of the refractive index of gold decreases by δ = 0.000511, and the imaginary part is β = 0.000106. Substituting the above parameter values ​​into formula (10), the second-order efficiency of the zone plate can be calculated to be 31.2%. When the focal length f1 = 10 mm, Figure 7 and Figure 8 The possible outline designs of the five radial zones of the zone plate are given respectively. Considering that the gradual change of the metal thickness is difficult to control in the actual processing, the zone plate can be designed with local steps of equal thickness.

[0122] According to an embodiment of the present disclosure, taking a ring zone with five step thicknesses as an example, the five thicknesses are 122 nanometers, 366 nanometers, 610 nanometers, 854 nanometers and 1098 nanometers respectively.

[0123] Another aspect of the disclosed embodiments provides a high-order diffraction zone plate, which may include multiple adjacent annular zones. The optical path length of light emitted from a light source through the same annular zone to the imaging point is the same, while the optical path length difference between light emitted from different annular zones to the imaging point is an integer multiple of the wavelength of the light. The preset radius of the annular zone is determined based on the compensation phase difference and optical path length formula, and the compensation phase difference is determined based on the preset phase, the wavelength of light, and the optical path length corresponding to the annular zone. The preset thickness of the annular zone is determined based on the complex refractive index of the zone plate and the compensation phase difference.

[0124] According to an embodiment of the present disclosure, in the process of preparing the wave zone plate, the preset radius and preset thickness of adjacent ring zones are compensated by compensating the phase difference, so that the optical path difference between the two adjacent ring zones is an integer multiple of the wavelength of light, so that the X-rays from the two adjacent ring zones reaching the imaging point will not produce phase cancellation, thereby improving the diffraction efficiency during high-order diffraction imaging.

[0125] Another aspect of the embodiments of the present disclosure provides an optical lens, which may include a zone plate prepared according to the preparation method described above, or the zone plate described above.

[0126] According to embodiments of the present disclosure, during the preparation of the zone plate, the preset radius and thickness of adjacent zones are compensated for by compensating for phase differences, so that the optical path difference between two adjacent zones is an integer multiple of the wavelength of light. This prevents X-rays from the two adjacent zones from experiencing phase cancellation when reaching the imaging point, thereby improving the diffraction efficiency during high-order diffraction imaging. By using such a zone plate, the optical lens disclosed herein can produce images with excellent imaging effects.

[0127] According to an embodiment of the present disclosure, the optical lens includes a Kinoform lens.

[0128] It should be noted that the zone plate provided by the present disclosure can also be applied to other devices, including but not limited to X-ray nano-microscopes and focusing elements.

[0129] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for preparing a zone plate, the zone plate comprising a plurality of adjacent annular zones, the method comprising: Determining a preset position corresponding to the annular zone according to a compensation phase difference and an optical path formula; Determining a preset radius of the annular zone according to the preset position, wherein the compensating phase difference is determined according to a preset phase, a wavelength of light, and an optical path corresponding to the annular zone; The compensating phase difference is used to ensure that the optical path length of light reaching the imaging point through the same annular zone is the same, while the optical path length difference reaching the imaging point through different annular zones is an integer multiple of the wavelength of the light, and the optical path length formula represents the relationship between the radius parameter of each annular zone and the optical path length; determining a reduction in the real part of the refractive index of the zone plate according to the complex refractive index of the zone plate; Determining a preset thickness of the annular zone according to the reduction amount of the real part of the refractive index and the compensating phase difference; For each of the annular zones, an annular zone with the preset radius and the preset thickness is prepared at the preset position of the zone plate, wherein the preset thickness enables the light passing through all positions of the zone plate to be phase-synchronized at the imaging point.

2. The method according to claim 1, wherein The optical path formula is determined based on the imaging formula of the zone plate, and the parameters of the imaging formula include the zone plate The object distance represents the distance between the zone plate and the light emitting point, and the image distance represents the distance between the zone plate and the imaging point.

3. The method according to claim 2, wherein: The optical path formula is determined based on the imaging formula of the zone plate, including: Determine the zone plate according to the imaging formula step focal length, the object distance and the image distance; According to the zone plate The optical path formula is determined by the step focal length, the object distance and the image distance.

4. The method according to claim 2 or 3, wherein: The imaging formula is shown in formula (1): （1） in, Characterizing Zone Plates Step focal length, Represents object distance, Characterize image distance; The optical path formula is shown in formula (2): （2） in, Characterizing Zone Plates The optical path length during the first-order imaging is Characterize the luminous point, Characterize the imaging point, Characterizes the intersection of the light emitted by the luminous point and the ring band during imaging, The radius parameter that characterizes the annulus; The compensation phase difference As shown in formula (3): （3） in, Represents any positive integer, Characterize the preset phase, , Characterizes the wavelength of light, for right Find the remainder.

5. The method according to claim 1, wherein The preset position is shown in formula (4): （4） in, Characterizing Zone Plates Step focal length, The radius parameter that characterizes the annulus; Characterizes integer multiples of wavelength; Preset radius of the ring The calculation of is shown in formula (5): （5） The preset thickness The calculation of is shown in formulas (6) and (7): （6） （7） in, Characterize the complex refractive index of the zone plate, Characterizing the real part of the complex refractive index, Characterizes the decrease in the real part of the refractive index, Characterizing the imaginary part of the complex refractive index, Represents the imaginary unit, Parameters that characterize the absorption coefficient of zone plate materials to light.

6. A high-order diffraction zone plate comprising: A plurality of adjacent annular zones, wherein the optical path length of light emitted from a light-emitting point from the same annular zone to the imaging point is the same, and the optical path length difference from light emitted from different annular zones to the imaging point is an integer multiple of the wavelength of the light; The preset radius of the annular zone is determined based on a preset position corresponding to the annular zone according to a formula for compensating phase difference and optical path, and is determined based on the preset position, and the compensating phase difference is determined based on a preset phase, light wavelength, and the optical path corresponding to the annular zone; The preset thickness of the annular zone is determined by determining a reduction in the real part of the refractive index of the zone plate according to the complex refractive index of the zone plate, and is determined according to the reduction in the real part of the refractive index and the compensating phase difference.

7. An optical lens comprising: A zone plate prepared by the preparation method according to any one of claims 1 to 5; Or the zone plate as claimed in claim 6.

8. The lens according to claim 7, wherein: The optical lens includes a Kinoform lens.

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