Single-stage diffraction grating structure and preparation method thereof

Abstract

The invention provides a single-stage diffraction grating structure and a preparation method thereof. The preparation method comprises the following steps: providing a substrate; the convolutional neural network based on a deep learning algorithm determines parameters of the periodically arranged hexagonal hole structure; and preparing a plurality of hexagonal hole structures which are periodically arranged on the surface of the substrate to form a single-stage diffraction grating structure, so that the single-stage diffraction grating structure has the diffraction characteristic of a sine diffraction grating. The preparation method of the single-stage diffraction grating structure can be compatible with a traditional semiconductor technology, the manufacturing technology is simple, the diffraction characteristic of a sine diffraction grating is achieved through etching of a grating unit structure composed of a periodic hexagonal hole structure, and the prepared single-stage diffraction grating structure has the characteristic of restraining high-order diffraction; clear positive and negative first-order diffraction images are obtained, reading errors are reduced, and spectral characteristics can be better analyzed.

Description

Technical Field

[0001] The present invention relates to the technical field of diffraction optical elements, and in particular to a single-stage diffraction grating structure and a preparation method thereof. Background Art

[0002] Light can deviate from a straight path. A typical example is when light passes through a small hole, and unexpected light appears in the shadow behind the hole, demonstrating the properties of light as an electromagnetic wave. This propagation around obstacles is called diffraction. Diffraction redistributes light intensity, creating alternating light and dark stripes. Light also appears where it shouldn't. This redistribution is particularly pronounced at edges, blurring the boundaries.

[0003] A diffraction grating is an optical element with a periodic structure that can split and demultiplex incident light waves through the interference and diffraction effects of light. In recent years, the rapid development of fields such as spectral analysis, optical communications, laser processing, and optical sensing has placed higher demands on efficient and precise diffractive optical elements. Against this backdrop, diffraction gratings, especially single-stage diffraction gratings due to their simple structure and ease of fabrication, have attracted widespread attention.

[0004] When the incident light is non-monochromatic, the high-order diffraction produced by traditional diffraction gratings is always superimposed on the useful low-order diffraction, which complicates the subsequent spectral decoding and affects the spectral purity and measurement accuracy of the system. In contrast, single-order diffraction gratings, through specific structural design and periodic control, retain only the positive and negative first-order diffraction required for the application, which can significantly suppress high-order diffraction, improve the utilization efficiency of light energy, and optimize beam quality. This high-order diffraction suppression property is very promising for applications in fields such as synchrotron radiation, astrophysics, and soft X-ray lasers.

[0005] Existing single-stage diffraction gratings suppress high-order diffraction by adjusting their structural dimensions. However, the relationship between structural dimensions and the diffraction pattern cannot be accurately explained using simple mathematical formulas. Furthermore, these design methods are overly complex and require continuous adjustment and optimization of structural parameters. Therefore, existing single-stage diffraction grating structures have not yet reached optimality, and there is an urgent need to explore better methods to achieve efficient single-stage diffraction gratings. Summary of the Invention

[0006] The first object of the present invention is to provide a method for preparing a single-order diffraction grating structure, so as to solve the problem in the prior art that the diffraction grating generates positive and negative first-order diffraction while also having interference from higher-order diffraction.

[0007] A second object of the present invention is to provide a single-stage diffraction grating structure.

[0008] The present invention provides a method for preparing a single-stage diffraction grating structure, comprising:

[0009] providing a substrate;

[0010] A convolutional neural network based on a deep learning algorithm determines the parameters of the periodically arranged hexagonal hole structure;

[0011] A plurality of periodically arranged hexagonal hole structures are prepared on the surface of the substrate to form a single-order diffraction grating structure, so that the single-order diffraction grating structure has the diffraction characteristics of a sinusoidal diffraction grating.

[0012] According to the method for preparing a single-stage diffraction grating structure provided by the present invention, a convolutional neural network based on a deep learning algorithm determines a periodic hexagonal hole structure, specifically comprising:

[0013] providing a periodically arranged hexagonal diffraction grating pattern and a target axial diffraction intensity distribution diagram on an observation plane;

[0014] Dividing the hexagonal diffraction grating pattern into a plurality of rectangular areas, each of the rectangular areas having a hexagonal structure;

[0015] The target axial diffraction intensity distribution map on the observation plane is input into the deep learning model of the convolutional neural network architecture to calculate the parameters corresponding to the hexagonal hole structure, thereby forming a design layout.

[0016] The axial diffraction intensity distribution diagram on the observation plane includes:

[0017] Clear zero-order diffraction and positive and negative first-order diffraction intensities;

[0018] Diffraction of the third and higher orders is suppressed to the background noise level.

[0019] Among them, the side lengths of each rectangular area are P x and P y , P x and P y Both are 20μm.

[0020] According to the method for preparing a single-order diffraction grating structure provided by the present invention, the hexagons in each of the rectangular regions are regarded as a combination of a rectangle and two identical triangles, wherein:

[0021] The base of the triangle is the long side of the rectangle, and the base of the triangle and the long side of the rectangle are equal to the length of the side of the rectangular area;

[0022] The height of the triangle is a, and the width of the rectangle is 2b;

[0023] Based on the trained convolutional neural network, by inputting the target axial diffraction intensity distribution map on the observation plane, the parameters a and b of the periodically arranged hexagonal hole structure that can suppress high-order diffraction can be obtained.

[0024] The parameter a has a generation range of 0 to 2.5 μm, and the parameter b has a generation range of 3.75 to 6.25 μm.

[0025] According to the method for preparing a single-stage diffraction grating structure provided by the present invention, according to the parameters of each hexagonal hole structure in the design layout, the periodically arranged hexagonal hole structure is etched correspondingly on the substrate to form the single-stage diffraction grating structure.

[0026] According to the method for preparing a single-stage diffraction grating structure provided by the present invention, etching a periodically arranged hexagonal hole structure on the substrate to form the single-stage diffraction grating structure specifically includes:

[0027] preparing a chrome plating layer on the surface of the substrate;

[0028] Spin-coating a photoresist layer on the surface of the chrome-plated layer and baking it on a hot plate;

[0029] Transferring the grating pattern on the design layout to the photoresist by laser direct writing lithography;

[0030] etching the hexagonal hole structure on the chrome plating layer by wet etching to form the grating pattern;

[0031] The remaining photoresist layer is removed.

[0032] When baking on a hot plate, the baking temperature is 150° C. and the baking time is 2 minutes.

[0033] The present invention also provides a single-stage diffraction grating structure, which is prepared using the above-mentioned single-stage diffraction grating structure preparation method. The single-stage diffraction grating structure includes a quartz substrate and a chrome-plated layer arranged on the quartz substrate. A plurality of periodically arranged hexagonal hole structures are provided on the chrome-plated layer to form a plurality of equally spaced grating unit structures.

[0034] The single-order diffraction grating structure preparation method provided by the present invention is compatible with traditional semiconductor processes and has a simple manufacturing process. The diffraction characteristics of the sinusoidal diffraction grating are achieved by etching a grating unit structure composed of a periodic hexagonal hole structure. The prepared single-order diffraction grating structure has the characteristic of suppressing high-order diffraction, obtaining clear positive and negative first-order diffraction images, reducing reading errors, and enabling better analysis of spectral characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 Flowchart of a method for preparing a single-stage diffraction grating structure in the first embodiment of the present invention;

[0037] Figure 2 is a schematic diagram of a hexagonal diffraction grating in the first embodiment of the present invention;

[0038] Figure 3 Schematic diagram of dividing the hexagonal diffraction grating pattern in the first embodiment of the present invention;

[0039] Figure 4 Schematic diagram of parameters of the hexagonal structure in the first embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the hierarchy after step S351 in the first embodiment of the present invention;

[0041] Figure 6 Schematic diagram of the hierarchy after step S352 in the first embodiment of the present invention;

[0042] Figure 7 Schematic diagram of the hierarchy after step S353 in the first embodiment of the present invention;

[0043] Figure 8 Schematic diagram of the hierarchy after step S354 in the first embodiment of the present invention;

[0044] Figure 9 is a schematic diagram of a single-stage diffraction grating structure in the second embodiment of the present invention;

[0045] Figure 10 Schematic diagram comparing the axial diffraction intensity distribution of the single-stage diffraction grating structure and the traditional diffraction grating in the second embodiment of the present invention.

[0046] Description of reference numerals:

[0047] 1: Substrate;

[0048] 2: Chrome plating;

[0049] 3: Photoresist layer. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention.

[0052] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0053] Due to their unique optical properties, such as phase matching, dispersion, polarization, and beam splitting, gratings have been widely used in optical communications, augmented reality / virtual reality (AR / VR) displays, synchrotron radiation, inertial confinement fusion, astrophysics, and extreme ultraviolet interferometry lithography. However, according to the grating equation, when the incident light is non-monochromatic, the diffraction spectrum does not correspond one-to-one with the wavelength. Higher-order diffraction spectra are always superimposed on the positive and negative first-order diffraction spectra, which hinders the subsequent decoding of the spectrum.

[0054] Sinusoidal diffraction gratings can suppress high-order diffraction and retain only the 0th order and positive and negative 1st order diffraction. However, sinusoidal diffraction gratings are usually three-dimensional structures. Due to the limitations of standard planar semiconductor processes and processing, it is difficult to manufacture sinusoidal diffraction gratings. The transmittance of the currently proposed single-order diffraction grating is close to the sinusoidal distribution, which can achieve a single-order diffraction effect. These diffraction optical elements suppress high-order diffraction by adjusting the structural size, but the relationship between the structural size and the diffraction pattern cannot be accurately explained by a simple mathematical formula. In addition, these design methods are too complex and require continuous adjustment and optimization of structural parameters. The currently used structure has not yet reached the optimal level, and better methods need to be explored to achieve efficient single-order diffraction gratings.

[0055] Therefore, in order to solve the above problems, the first embodiment of the present invention provides a method for preparing a single-stage diffraction grating structure, which utilizes the preparation of a single-stage diffraction grating structure composed of a periodic hexagonal structure to make it exhibit the characteristics of a sinusoidal diffraction grating, meet the requirements for positive and negative first-order diffraction, reduce the difficulty and error of reading, and better analyze the spectral characteristics.

[0056] Figure 1 The flowchart of the method for preparing a single-stage diffraction grating structure in this embodiment is shown. The method for preparing a single-stage diffraction grating structure includes at least the following steps:

[0057] S10, providing a substrate.

[0058] The substrate in this embodiment is a quartz substrate, that is, a glass substrate. A hexagonal diffraction grating structure is formed by etching a periodically arranged hexagonal hole structure on the surface of the substrate. The thickness of the substrate only needs to meet the etching requirements.

[0059] S20, determining structural parameters of the hexagonal pore structure to be prepared according to the target axial diffraction intensity distribution diagram on the observation plane.

[0060] The structural parameters of the single-stage diffraction grating determine the final far-field diffraction image. By inputting the target axial diffraction intensity distribution map on the observation plane into the trained convolutional neural network, the structural parameters a and b of the grating unit structure of the single-stage diffraction grating that can suppress high-order diffraction can be obtained. This is because: deep learning constructs complex models through multi-layer neural networks and has powerful data fitting capabilities, which enables deep learning to capture nonlinear relationships in data and improve the accuracy of model predictions; deep learning can automatically extract key features from data without manual design. This embodiment mainly adjusts the target axial diffraction intensity distribution map on the observation plane, and the corresponding results of the trained convolutional neural network will also change accordingly.

[0061] S30, preparing a plurality of periodically arranged hexagonal hole structures on the surface of the substrate to form a single-order diffraction grating structure, so that the single-order diffraction grating structure has the characteristics of a sinusoidal diffraction grating.

[0062] Due to the three-dimensional structural limitations of sinusoidal diffraction gratings, their fabrication is subject to process and machining precision, resulting in significant manufacturing complexity. The grating unit structure of the single-stage diffraction grating of this embodiment consists of periodically arranged hexagonal structures, which are periodically distributed across the substrate surface. This allows the resulting single-stage diffraction grating structure to exhibit the same properties as a sinusoidal diffraction grating, eliminating high-order diffraction. Furthermore, conventional planar semiconductor fabrication processes can be directly used to fabricate the aperture structure, making integration and manufacturing easy and simple. Compared to conventional sinusoidal diffraction gratings, this fabrication process offers significantly improved precision.

[0063] In the actual implementation process, this embodiment designs and prepares the hexagonal hole structure according to the axial diffraction intensity distribution diagram on the observation plane. The specific preparation process is as follows:

[0064] S31, provides a hexagonal diffraction grating pattern and a target axial diffraction intensity distribution on an observation plane. Figure 2 A schematic diagram of a hexagonal diffraction grating layout is shown.

[0065] S32, divide the hexagonal diffraction grating pattern into multiple rectangular areas, and the side lengths of each rectangular area are P x and P y . Figure 3 A schematic diagram of the division of the hexagonal diffraction grating pattern is shown, where the red ellipse indicates that there is a hexagonal hole structure in each rectangular area.

[0066] Specifically, each hexagon in a rectangular area is considered to be composed of a rectangle and two identical triangles, symmetrically placed on the left and right sides of the rectangle. The parameters are as follows: the base of the triangle is the length of the rectangle, and the values of these two parameters are equal to the side lengths of the rectangular area; the height of the triangle is set to a, the width of the rectangle is set to 2b, and the length of the rectangle (i.e., the length of the base of the triangle) is set to c. Figure 4 Schematic diagram of the parameters of the hexagonal structure.

[0067] S33, based on the trained convolutional neural network, by inputting the target axial diffraction intensity distribution map on the observation plane, the parameters a and b of the hexagonal hole structure that can suppress high-order diffraction can be obtained.

[0068] Numerical simulations were performed for hexagonal aperture structures with different a and b values. The far-field diffraction intensity distribution is related to the structural parameters a and b within the periodic hexagonal aperture structure, and its distribution can be altered by adjusting these parameters. Selecting appropriate structural parameters can transform the transmittance function of a single-order diffraction grating structure into a sinusoidal function, resulting in a far-field diffraction intensity distribution consisting of only zero-order and first-order diffraction, thus achieving single-order diffraction characteristics for the single-order diffraction grating structure.

[0069] Specifically, in the simulation, P x and P y Both are 20μm. The generation ranges of a and b are 0-2.5μm and 3.75-6.25μm, respectively, and the adjacent intervals are all 0.025μm. 90% of the data is used to train the deep learning model, and the remaining 10% of the data is used to test the performance after training. The target axial diffraction intensity distribution map on the observation plane is input into the trained convolutional neural network, and a set of parameters (a=2.1μm, b=4.7μm) is obtained from the trained convolutional neural network to form a design layout and obtain the corresponding far-field diffraction intensity.

[0070] S35, preparing a hexagonal hole structure on the substrate according to the structural parameters of each hexagon in the design layout.

[0071] After obtaining the design layout, the corresponding hexagonal hole structure can be prepared on the substrate according to the structural parameters of the hexagon in the design layout, so that the single-order diffraction grating structure formed after all the hexagonal hole structures are prepared has the same characteristics as the sinusoidal diffraction grating to eliminate high-order diffraction.

[0072] Specifically, according to the structural parameters of each hexagon in the design layout, the steps for preparing the hexagonal hole structure on the substrate are as follows:

[0073] S351 , preparing a chrome plating layer 2 on the surface of the substrate 1 .

[0074] The chromium plating layer 2 prepared in this embodiment is mainly used to protect the substrate during the subsequent etching process. Figure 5 It should be noted that the thickness of the chrome plating layer 2 is usually about 150 nanometers, to prevent the chrome plating layer from being too thin, which may not provide adequate protection, and from being too thick, which may result in material waste.

[0075] S352 , spin-coating a photoresist layer 3 on the surface of the chrome-plated layer 2 , and transferring the grating pattern to the photoresist layer 3 .

[0076] When the photoresist layer 3 is spin-coated on the surface of the chrome-plated layer 2, it is necessary to bake it on a hot plate at 150°C for 2 minutes and then use a laser direct writing photolithography process to transfer the grating pattern to the photoresist layer 3 through steps such as exposure and development. Figure 6 shown.

[0077] S353 , transferring the grating pattern to the chrome layer 2 by wet etching.

[0078] After the photolithography process is completed, the chrome plating layer 2 can be etched by wet etching. The portion covered by the photoresist will not be etched because it will not be exposed to the etching solvent, while the exposed portion of the chrome plating layer 2 will be removed by the etching solvent to form a grating pattern. Figure 7 shown.

[0079] S354, removing the remaining photoresist layer 3.

[0080] After the etching of the substrate is completed, the remaining photoresist layer 3 is removed to obtain a single-stage diffraction grating structure with a periodically arranged hexagonal structure, such as Figure 8 It should be noted that the remaining layers can be removed by wet stripping, which corresponds to photoresist removal. The solutions used in wet stripping are acetone, anhydrous ethanol, and deionized water, respectively, and finally dried by nitrogen.

[0081] The method for preparing the single-stage diffraction grating structure of this embodiment is compatible with traditional semiconductor processes and has a simple manufacturing process. The characteristics of the sinusoidal diffraction grating are realized by etching the single-stage diffraction grating structure, so that the prepared single-stage diffraction grating structure has the characteristic of suppressing high-order diffraction. At the same time, by training a convolutional neural network and inputting the target axial diffraction intensity distribution on the observation surface, the periodic hexagonal structure parameters that can suppress high-order diffraction and retain clear positive and negative first-order diffraction images are obtained, thereby reducing reading errors and better analyzing spectral characteristics.

[0082] Based on the same inventive concept, the second embodiment of the present invention provides a single-stage diffraction grating structure, which is prepared using the single-stage diffraction grating structure preparation method of the above embodiment. It has a simple structure and can eliminate high-order diffraction to obtain clear positive and negative first-order diffraction images, reduce reading errors, and better analyze spectral characteristics. Figure 9 A physical picture of a single-stage diffraction grating structure is shown, where the value in the lower left corner is the range.

[0083] like Figure 9 As shown, the dark area corresponds to the chrome-plated layer area with a transmittance of 0, and the light area corresponds to the quartz substrate area with a transmittance of 1. That is, the single-stage diffraction grating structure includes a quartz substrate and a chrome-plated layer disposed on the quartz substrate. The chrome-plated layer is provided with a plurality of periodically arranged hexagonal hole structures to form a plurality of equally spaced grating unit structures.

[0084] In fact, Figure 9 The dimensions of each hexagon in should correspond to Figure 3The size of the hexagon in the middle ellipse is usually determined according to the equipment precision of the semiconductor process, for example, a = 2.1 μm, b = 4.7 μm, that is, the length of the upper and lower sides of the hexagon is 9.4 μm, and the distance between the two middle points is 13.6 μm. Figure 3 The hexagonal structure is only for illustration, and its size is obviously larger than Figure 8 The structural parameters of the medium hexagonal structure should not be used as the basis for the design of hexagonal structural parameters.

[0085] Figure 10 A schematic diagram comparing the light intensity on the observation surface of the single-stage diffraction grating structure in this embodiment and the traditional diffraction grating structure is shown; based on the schematic diagram, it can be seen that the single-stage diffraction grating structure in this embodiment effectively eliminates high-order diffraction and has good performance in positive and negative first-order diffraction.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a single-stage diffraction grating structure, characterized in that: include: providing a substrate; A convolutional neural network based on a deep learning algorithm determines the parameters of the periodically arranged hexagonal hole structure; A plurality of periodically arranged hexagonal hole structures are prepared on the surface of the substrate to form a single-order diffraction grating structure, so that the single-order diffraction grating structure has the diffraction characteristics of a sinusoidal diffraction grating.

2. The method for preparing a single-stage diffraction grating structure according to claim 1, wherein: The convolutional neural network based on deep learning algorithm determines the periodic hexagonal hole structure, specifically including: providing a periodically arranged hexagonal diffraction grating pattern and a target axial diffraction intensity distribution diagram on an observation plane; Dividing the hexagonal diffraction grating pattern into a plurality of rectangular areas, each of the rectangular areas having a hexagonal structure; The target axial diffraction intensity distribution map on the observation plane is input into the deep learning model of the convolutional neural network architecture to calculate the parameters corresponding to the hexagonal hole structure, thereby forming a design layout.

3. The method for preparing a single-stage diffraction grating structure according to claim 2, wherein: The axial diffraction intensity distribution diagram on the observation plane includes: Clear zero-order diffraction and positive and negative first-order diffraction intensities; Diffraction of the third and higher orders is suppressed to the background noise level.

4. The method for preparing a single-stage diffraction grating structure according to claim 2, wherein: The side lengths of each rectangular area are P x and P y , P x and P y Both are 20μm.

5. The method for preparing a single-stage diffraction grating structure according to claim 2, wherein: Each hexagon in the rectangular area is considered to be composed of a rectangle and two identical triangles, where: The base of the triangle is the long side of the rectangle, and the base of the triangle and the long side of the rectangle are equal to the length of the side of the rectangular area; The height of the triangle is a, and the width of the rectangle is 2b; Based on the trained convolutional neural network, by inputting the target axial diffraction intensity distribution map on the observation plane, the parameters a and b of the periodically arranged hexagonal hole structure that can suppress high-order diffraction can be obtained.

6. The method for preparing a single-stage diffraction grating structure according to claim 5, wherein: The generation range of the parameter a is 0 to 2.5 μm, and the generation range of the parameter b is 3.75 to 6.25 μm.

7. The method for preparing a single-stage diffraction grating structure according to claim 2, wherein: According to the parameters of each hexagonal hole structure in the design layout, etching of the corresponding periodically arranged hexagonal hole structures is performed on the substrate to form the single-order diffraction grating structure.

8. The method for preparing a single-stage diffraction grating structure according to claim 7, wherein: Etching a periodically arranged hexagonal hole structure on the substrate to form the single-stage diffraction grating structure includes: preparing a chrome plating layer on the surface of the substrate; Spin-coating a photoresist layer on the surface of the chrome-plated layer and baking it on a hot plate; Transferring the grating pattern on the design layout to the photoresist by laser direct writing lithography; etching the hexagonal hole structure on the chrome plating layer by wet etching to form the grating pattern; The remaining photoresist layer is removed.

9. The method for preparing a single-stage diffraction grating structure according to claim 8, wherein: When baking on a hot plate, the baking temperature is 150° C. and the baking time is 2 minutes.

10. A single-stage diffraction grating structure, characterized in that: The single-stage diffraction grating structure is prepared using the method for preparing a single-stage diffraction grating structure according to any one of claims 1 to 9, wherein the single-stage diffraction grating structure includes a quartz substrate and a chrome-plated layer arranged on the quartz substrate, and a plurality of periodically arranged hexagonal hole structures are provided on the chrome-plated layer to form a plurality of equally spaced grating unit structures.

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