Grating preparation equipment

Abstract

The utility model relates to the technical field of diffractive optical components, in particular to grating preparation equipment which is used for exposing a grating base material to form a grating and comprises a light source module, a bearing table and a movement mechanism. The light source module is used for emitting first coherent light and second coherent light; the bearing table is used for bearing a grating substrate, and the first coherent light and the second coherent light interfere with each other on the grating substrate to form an interference exposure field; the movement mechanism is connected to the bearing table and comprises a first direction movement mechanism, the first direction movement mechanism is used for driving the bearing table to reciprocate between a first position and a second position in the first direction, and the first direction is consistent with the normal direction of the bearing table. Through the arrangement, the reciprocating scanning motion of the motion mechanism in the normal direction of the bearing table is increased, the smoothing effect on the grating microstructure is achieved, the high-frequency error in the first coherent light and the second coherent light can be reduced, and therefore the low-stray-light diffraction holographic grating can be conveniently prepared.

Description

Technical Field

[0001] This application relates to the technical field of diffractive optical elements, and particularly to a grating preparation device. Background Art

[0002] Holographic gratings are important diffractive optical elements and can be applied in many fields such as AR diffractive optical waveguides, precision measurement, spectroscopic beam spectral measurement equipment, laser pulse compression, and space laser optics. Currently, existing methods for preparing diffractive gratings include electron beam direct writing lithography, Talbot lithography, nanoimprint lithography, and double-beam or multi-beam exposure methods. Among them, laser interference lithography is one of the most widely used tools. It can quickly fabricate periodic nano-grating patterns without using a mask. A laser double-beam interference exposure system can directly perform double-beam exposure of periodic grating structures of semiconductor materials such as photoresist on a standard substrate, featuring a simple optical path, high precision, high efficiency, and strong resistance to external environmental disturbances.

[0003] Stray light generally refers to the unexpected light in an optical system, also known as optical "noise". Stray light will cause extra light in the image, thereby reducing the imaging quality. As the detection requirements of optical systems become higher and higher, stray light will affect the performance of optical systems, reduce imaging contrast and picture quality, and even affect signals. Therefore, the requirements for analyzing and suppressing stray light have gradually received attention and have also become one of the necessary links in the image quality detection of optical systems.

[0004] Holographic gratings prepared by traditional exposure methods generally have surface defects. For example, various lens combinations used in the optical path system will increase unnecessary aberrations. In addition, the speckle characteristics of the laser itself will also lead to various defects in the prepared holographic gratings, such as groove type errors of the grating at the microscopic level, bending of the grating lines on the sidewalls of the grating, and surface roughness. These defects will cause the generation of stray light in the grating, thereby reducing the image resolution. For the interference exposure system, this system also has speckle caused by laser coherence and stray light caused by scattering of optical elements, which will all cause defects in the exposure interference field and are recorded on the photoresist through the exposure process, resulting in problems such as bending of grating lines and large surface roughness in the grating at the microscopic level. Therefore, low stray light of holographic gratings has always been an important technical performance pursued in the process of preparing holographic gratings. Summary of the Utility Model

[0005] The present application provides a grating preparation device for exposing a grating substrate to form a grating. The grating preparation device includes a light source module, a carrier table, and a motion mechanism; the light source module is used to emit a first coherent light and a second coherent light; the carrier table is used to carry the grating substrate, and the first coherent light and the second coherent light interfere on the grating substrate to form an interference exposure field; the motion mechanism is connected to the carrier table, and the motion mechanism includes a first-direction motion mechanism for driving the carrier table to reciprocate between a first position and a second position along a first direction, and the first direction is consistent with the normal direction of the carrier table.

[0006] Optionally, in some embodiments, the grating preparation device further includes a phase modulator electrically connected to the light source module and used to adjust the optical path difference between the first coherent light and the second coherent light.

[0007] Optionally, in some embodiments, the phase modulator includes a detection unit and a modulation unit. The detection unit is used to detect the interference fringe information generated after the combination of the first coherent light and the second coherent light, and the modulation unit is used to modulate the optical path difference between the first coherent light and the second coherent light according to the interference fringe information collected by the detection unit.

[0008] Optionally, in some embodiments, the detection unit includes a light combination unit and a detection unit. The light combination unit is disposed on the optical paths of the first coherent light and the second coherent light and is used to combine the first coherent light and the second coherent light to form interference fringe information, and the detection unit is used to detect the interference fringe information.

[0009] Optionally, in some embodiments, the distance range of the first position and the second position along the first direction is greater than or equal to 90 nm and less than or equal to 110 nm.

[0010] Optionally, in some embodiments, the grating preparation device further includes a mask disposed on the light output optical path of the light source module, between the light source module and the carrier table. The distance range of the mask from the surface of the grating substrate facing away from the carrier table in the first direction is greater than or equal to 10 μm and less than or equal to 1000 μm.

[0011] Optionally, in some embodiments, the first-direction motion mechanism includes at least one of a piezoelectric inertial ceramic, an acousto-optic modulator, or an electro-optic modulator.

[0012] Optionally, in some embodiments, the carrier table has a central axis; the motion mechanism further includes a rotation mechanism connected to the carrier table and used to drive the carrier table to rotate around the central axis or reciprocally rotate between a third position and a fourth position around the central axis to change the angle between the first coherent light and the second coherent light and the central axis of the interference exposure field.

[0013] Optionally, in some embodiments, the motion mechanism further includes a second-direction translation mechanism, which is configured to drive the carrier stage to translate in the second direction to achieve stitching of multiple interference exposure fields in the second direction. The second direction is consistent with the extension direction of the plane where the grating substrate is located on the carrier stage.

[0014] Optionally, in some embodiments, the motion mechanism further includes a third-direction translation mechanism, which is configured to drive the carrier stage to translate in the third direction to achieve stitching of multiple interference exposure fields in the third direction. The third direction is consistent with the extension direction of the plane where the grating substrate is located on the carrier stage, and intersects or is perpendicular to the second direction.

[0015] In the grating preparation device provided by the present application, since a first-direction motion mechanism is provided, and the first-direction motion mechanism is configured to drive the carrier stage to reciprocate between a first position and a second position in the first direction, and the first direction is consistent with the normal direction on the carrier stage, therefore, during the grating preparation process, the motion mechanism can drive the grating substrate to perform a reciprocating scanning motion along the normal direction of the carrier stage, which can reduce the high-frequency errors in the first coherent light and the second coherent light, achieve a smoothing effect on the grating microstructure, thereby reducing stray light, so as to prepare a diffraction holographic grating with low stray light. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the present application, the drawings required for implementation will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 is a schematic structural diagram of a grating preparation device in some embodiments of the present application.

[0018] Figure 2 is used to illustrate Figure 1 the equivalent distribution diagram of the moving position of the exposure plane in the first direction in

[0019] Figure 3 is a schematic structural diagram of a grating preparation device in other some embodiments of the present application.

[0020] Figure 4 is Figure 1 a schematic topographic diagram of a straight grating fabricated by the grating preparation device shown in

[0021] Figure 5 is the equivalent light intensity distribution diagram in the second direction X.

[0022] Figure 6 is Figure 1Schematic diagram for calculating the micro-displacement of the middle exposure plane in the first direction.

[0023] Figure 7 is Figure 3 Schematic diagram of the topography of the blazed grating fabricated by the grating fabrication device shown.

[0024] Label description: 100, grating fabrication device; 10, first coherent light; 20, second coherent light; 30, carrier stage; 40, motion mechanism; 50, first-direction motion mechanism; 60, exposure plane; 70, mask; 80, second-direction translation mechanism; 90, third-direction translation mechanism; 91, grating substrate; 93, grating microstructure; 95, central axis; 96, blazed grating; 97, straight grating. Specific embodiments

[0025] In order to enable those skilled in the art of the present technology to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of this application.

[0026] In the description of this application, it should be understood that the orientation or state relationship indicated by terms such as "length", "width", "thickness", "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is the orientation or state relationship based on the orientation or state relationship shown in the accompanying drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation.

[0027] Moreover, in addition to being able to represent the orientation or state relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0028] In addition, terms such as "first", "second", etc. are mainly used to distinguish different devices, components or constituent parts (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, components or constituent parts. Thus, features defined with "first", "second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0029] In addition, unless otherwise clearly specified or limited, terms such as "installed", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection, or indirectly connected through an intermediate medium, or it may be the communication inside two components, or it may be only surface contact. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0030] As certain terms are used in the description and claims to refer to specific components, those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. The description and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As the term "comprising" mentioned throughout the description and claims is an open-ended term, it should be interpreted as "including but not limited to"; "substantially" means that those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0031] Please refer to Figure 1 , embodiments of the present application provide a grating preparation device 100, which is used to expose a grating substrate 91 to form a grating. The above grating substrate 91 is a substrate coated with a photosensitive material. Among them, the photosensitive material may be a photosensitive resin, U glue or photoresist and other materials, and the substrate may be a silicon wafer, glass or quartz material sheet. In some embodiments, the photosensitive material is a photoresist, and the thickness of the photoresist is 50 - 500 nm (including the endpoints). Preferably, in other embodiments, the thickness of the photoresist may also be 100 - 400 nm (including the endpoints). When two coherent light beams meet on its surface and interfere, an interference exposure field will be generated. The surface of the grating substrate 91 located in the interference exposure field will be exposed to form a grating microstructure 93 (the groove structure shown on the surface of the grating substrate 91), so as to be able to record the interference pattern formed by interference to make a grating.

[0032] The grating preparation apparatus 100 includes a light source module (not shown), a carrier platform 30, and a motion mechanism 40. The light source module is used to emit first coherent light 10 and second coherent light 20, which are incident on the grating substrate 91 to form the interference exposure field. The carrier platform 30 is used to support the grating substrate 91. The motion mechanism 40 is connected to the carrier platform 30 and includes a first-direction motion mechanism 50. The first-direction motion mechanism 50 is used to drive the carrier platform 30 to reciprocate along a first direction Z, which is consistent with the normal O of the carrier platform 30.

[0033] With the above arrangement, during the grating preparation process of the grating preparation apparatus 100, the first-direction motion mechanism 50 drives the carrier 30 and the grating substrate 91 to continuously perform reciprocating scanning motion along the first direction Z (i.e., the direction of the normal O of the carrier 30), so that the interference exposure field generated by the interference of the first coherent light 10 and the second coherent light 20 continuously exposes the grating substrate 91 along the first direction Z to produce a grating microstructure 93 with a smooth inner wall, thereby reducing high-frequency errors in the first coherent light 10 and the second coherent light 20, thereby reducing stray light and producing a low-stray-light diffraction holographic grating.

[0034] In some embodiments, the first direction motion mechanism 50 may include at least one of a piezoelectric inertial ceramic, an acousto-optic modulator, or an electro-optic modulator, or may be any other motion driving mechanism.

[0035] In some embodiments, the grating substrate 91 has an exposure plane 60 parallel to the carrier 30. The exposure plane 60 is located on the side of the grating substrate 91 facing away from the carrier 30 and toward the light source module. The light source module is configured to emit a first coherent light 10 and a second coherent light 20. The first coherent light 10 and the second coherent light 20 interfere with each other on the exposure plane 60 to generate an interference exposure field. The grating substrate 91 located within the interference exposure field is exposed to form the aforementioned groove structure (i.e., the grating microstructure 93), thereby completing the fabrication of the grating structure. During actual exposure, due to the instability of the light source, high-frequency errors exist in the first coherent light 10 and the second coherent light 20, which further leads to burrs on the vertical walls of the formed grating structure grooves. When the grating substrate 91 is located at different positions in the first direction Z, the different optical path differences of the two coherent light beams cause different intensities of the interference exposure field formed by interference. Therefore, by driving the supporting platform 30 and the grating substrate 91 to move back and forth continuously along the first direction Z by the first direction movement mechanism 50, the influence of high-frequency errors on the grating structure grooves can be smoothed, so that the inner wall of the groove of the grating microstructure 93 along the first direction Z is smoother, so as to achieve the effect of reducing high-frequency errors in the first coherent light 10 and the second coherent light 20 and reducing stray light.

[0036] Please also refer to 1 and Figure 2, in some embodiments, the first-direction motion mechanism 50 is configured to drive the carrier stage 30 to reciprocate in the first direction Z. The stroke of the carrier stage 30 at the extreme positions of its motion in the first direction Z ( Figure 2 h1 in) ranges from: greater than or equal to 90 μm and less than or equal to 110 μm. Specifically, the carrier stage 30 has two extreme positions in its motion in the first direction Z, namely the first position and the second position. The exposure plane 60 (i.e., the illustrated reference position) is between the first position and the second position. It can be seen that each vibration of the carrier stage 30 in the first direction Z will cross the exposure plane to fully utilize the exposure opportunity and smooth the inner wall of the groove of the grating microstructure 93. As a specific example, the specific value of the stroke h1 of the carrier stage 30 at the extreme positions of its motion in the first direction Z can be: 90 μm, 92 μm, 94 μm, 96 μm, 98 μm, 100 μm, 102 μm, 104 μm, 106 μm, 108 μm, 110 μm, and any other value between 90 μm and 110 μm (including the endpoints). Through the above settings, since when the stroke h1 of the carrier stage 30 at the extreme positions of its motion in the first direction Z is less than 90 μm, the interference fringes generated by the first coherent light 10 and the second coherent light 20 cannot form a grating microstructure 93 with sufficient depth on the surface of the grating substrate 91, and when the stroke h1 of the carrier stage 30 at the extreme positions of its motion in the first direction Z is greater than 110 μm, the interference fringes generated by the first coherent light 10 and the second coherent light 20 cannot form a grating microstructure 93 with too deep a depth on the surface of the grating substrate 91. Therefore, in this embodiment, the stroke h1 of the carrier stage 30 in the first direction Z is limited between 90 μm and 110 μm (including the endpoints), which can ensure that a grating microstructure 93 with a reasonable depth is formed on the surface of the grating substrate 91 to meet the production and preparation requirements of a low stray light holographic grating.

[0037] Please refer to Figure 1 , in some embodiments, the grating preparation device 100 further includes a mask 70. The mask 70 is disposed on the light output path of the light source module, and the mask 70 is disposed between the light source module and the carrier stage 30. The mask 70 is used to block the non-exposed parts of the grating substrate 91 and allow the first coherent light 10 and the second coherent light 20 to pass through to perform interference exposure on the exposed parts of the grating substrate 91. The distance between the mask 70 and the surface of the grating substrate 91 facing away from the carrier stage 30 (i.e., the exposure plane 60) in the first direction Z ( Figure 1The range of h2) therein is: greater than or equal to 10 μm and less than or equal to 1000 μm. As a specific example, the specific value of the distance h2 in the first direction Z between the mask 70 and the surface of the grating substrate 91 facing away from the carrier stage 30 (i.e., the exposure plane 60) can be: 10 μm, 20 μm, 30 μm, 50 μm, 100 μm, 300 μm, 500 μm, 700 μm, 900 μm, 1000 μm, and any other value within 10 μm to 1000 μm (including the endpoints). Through the above settings, the mask 70 can ensure the uniformity of the target gratings in the effective area of the exposure system, which is beneficial to obtaining a high-quality topography of the holographic grating in the effective exposure area and achieving the design requirements of a low stray light holographic grating. Moreover, since when the distance h2 in the first direction Z between the mask 70 and the surface of the grating substrate 91 facing away from the carrier stage 30 (i.e., the exposure plane 60) is less than 10 μm or greater than 1000 μm, it will have a negative impact on the uniformity of the target gratings in the effective area of the exposure system. Therefore, in this embodiment, the distance h2 in the first direction Z between the mask 70 and the surface of the grating substrate 91 facing away from the carrier stage 30 (i.e., the exposure plane 60) is limited to between 10 μm and 1000 μm (including the endpoints), which can effectively ensure the uniformity of the target gratings in the effective area of the exposure system, and thus is beneficial to the preparation of a low stray light holographic grating.

[0038] Please refer to Figure 1, in some embodiments, the motion mechanism 40 further includes a second-direction translation mechanism 80. The second-direction translation mechanism 80 is configured to drive the carrier stage 30 to translate along the second direction X to achieve stitching of multiple interference exposure fields in the second direction X. The second direction X is consistent with the extension direction of the plane where the grating substrate 91 is located on the carrier stage 30. Through the above arrangement, during the process of preparing the grating by the grating preparation device 100, the second-direction translation mechanism 80 will drive the carrier stage 30 and the grating substrate 91 to translate along the second direction X, so that the interference fringes generated by the interference of the first coherent light 10 and the second coherent light 20 expose different regions of the grating substrate 91 along the second direction X. At the same time, combined with the reciprocating scanning movement of the first-direction motion mechanism 50 in the first direction Z, internal smooth grating microstructures 93 can be generated in different regions on the surface of the grating substrate 91. Therefore, the high-frequency errors in the first coherent light 10 and the second coherent light 20 can be reduced, thereby reducing stray light to fabricate a large-area diffraction grating with low stray light. In some embodiments, the second-direction translation mechanism 80 may include at least one of a piezoelectric inertial ceramic, an acousto-optic modulator, or an electro-optic modulator, and may also be any other motion driving mechanism. Since both the second-direction translation mechanism 80 and the first-direction motion mechanism 50 are connected to the carrier stage 30, when the second-direction translation mechanism 80 drives the carrier stage 30 to translate along the second direction X, the first-direction motion mechanism 50 can move synchronously with the carrier stage 30. Therefore, the movement of the carrier stage 30 and the grating substrate 91 along the first direction Z and the movement along the second direction X can be carried out synchronously or separately.

[0039] In some embodiments, the motion mechanism 40 further includes a third-direction translation mechanism 90. The third-direction translation mechanism 90 is configured to drive the carrier stage 30 to translate along the third direction Y to achieve stitching of multiple interference exposure fields in the third direction Y. The third direction Y is consistent with the extension direction of the plane where the grating substrate 91 is located on the carrier stage 30 and intersects or is perpendicular to the second direction. Through the above arrangement, during the process of fabricating the grating by the grating fabrication device 100, the third-direction translation mechanism 90 will drive the carrier stage 30 and the grating substrate 91 to translate along the third direction Y, so that the interference fringes generated by the interference of the first coherent light 10 and the second coherent light 20 expose different regions of the grating substrate 91 along the third direction Y. At the same time, combined with the reciprocating scanning movement of the first-direction motion mechanism 50 in the first direction Z and the translation movement of the second-direction translation mechanism 80 in the second direction X, more regions on the surface of the grating substrate 91 can generate grating microstructures 93 with smooth interiors. Therefore, the high-frequency errors in the first coherent light 10 and the second coherent light 20 can be reduced, thereby reducing stray light to fabricate a large-area diffraction grating with low stray light. In some embodiments, the third-direction translation mechanism 90 can be at least one of a piezoelectric inertial ceramic, an acousto-optic modulator, or an electro-optic modulator, and can also be any other motion driving mechanism. Since both the third-direction translation mechanism 90 and the first-direction motion mechanism 50 are connected to the carrier stage 30, when the third-direction translation mechanism 90 drives the carrier stage 30 to translate along the third direction Y, the first-direction motion mechanism 50 can move synchronously with the carrier stage 30. Therefore, the movement of the carrier stage 30 and the grating substrate 91 along the first direction Z and the movement along the third direction Y can be carried out synchronously or separately. Similarly, the movement of the carrier stage 30 and the grating substrate 91 along the second direction X and the movement along the third direction Y can be carried out synchronously or separately.

[0040] Please refer to Figure 1 , in some embodiments, the third direction Y (the direction perpendicular to the paper plane as shown in the figure) is perpendicular to the second direction X (the direction parallel to the paper plane as shown in the figure). In other embodiments, the third direction Y and the second direction X can also intersect but not be perpendicular.

[0041] Please refer to Figure 3 , in some embodiments, the carrier stage 30 has a central axis 95 (the direction perpendicular to the paper plane as shown in the figure). The motion mechanism 40 further includes a rotation mechanism (not shown in the figure). The rotation mechanism is connected to the carrier stage 30 and is configured to drive the carrier stage 30 to rotate around the central axis 95 or reciprocally rotate between a third position and a fourth position around the central axis 95 to change the angle between the first coherent light 10 and the second coherent light 20 and the central axis of the interference exposure field. Define the central axis of the interference exposure field as the line in the interference exposure field that is equidistant from the two coherent light beams, and the central axis of the interference exposure field is perpendicular to the grating substrate 91.

[0042] In a specific embodiment, the extending direction of the central axis 95 is consistent with the third direction Y. It should be noted that the third position and the fourth position are not shown in the accompanying drawings of the specification, and the third position and the fourth position represent two extreme positions where the moving mechanism 40 rotates around the central axis 95. Through the above arrangement, during the process of preparing the grating by the grating preparation device 100, the rotating mechanism can drive the carrier table 30 and the grating substrate 91 to rotate around the central axis 95, so as to realize the pose adjustment of the first coherent light 10 and the second coherent light 20 in the exposure plane 60, that is, to realize the adjustment of the angle θ1 between the first coherent light 10 and the central axis of the interference exposure field and the angle θ2 between the second coherent light 20 and the central axis of the interference exposure field. The angles between the two coherent lights and the central axis of the interference exposure field will affect the moving distance of the carrier table 30 in the first direction Z. When the angle between the first coherent light 10 and the central axis of the interference exposure field is 30 degrees and the angle between the second coherent light 20 and the central axis of the interference exposure field is 20 degrees, the carrier table 30 needs to move 578 nm in the first direction Z to achieve a smooth effect. When the angle between the first coherent light 10 and the central axis of the interference exposure field is 60 degrees and the angle between the second coherent light 20 and the central axis of the interference exposure field is 30 degrees, the carrier table 30 only needs to move 84 nm in the first direction Z to achieve a smooth effect. At the same time, during the actual operation process, due to the interference of environmental factors, it is very difficult to maintain the angles between the two coherent lights and the central axis of the interference exposure field at a fixed value. By making the carrier table 30 rotate reciprocally between the third position and the fourth position around the central axis 95 through rotation, the average value of the angles between the two coherent lights and the central axis of the interference exposure field can be kept almost unchanged within a period of time, which is beneficial to realizing the adjustment of the light intensity distribution of the light field. At the same time, it also enables the stroke of the extreme position of the carrier table 30 moving in the first direction Z ( Figure 2 h1 in) to be in the range of 90 μm to 110 μm (including the endpoints). When the rotating mechanism drives the carrier table 30 to rotate, the first-direction moving mechanism 50, the second-direction translation mechanism 80, and the third-direction translation mechanism 90 can all rotate synchronously with the carrier table 30 to ensure that the carrier table 30 and the grating substrate 91 can still move in the first direction Z, the second direction X, and the third direction Y during the rotation process; in other embodiments, they can also be carried out separately.

[0043] In some embodiments, the grating preparation device 100 further includes a phase modulator (not shown in the figure). The phase modulator is electrically connected to the light source module and is used to adjust the optical path difference between the first coherent light 10 and the second coherent light 20. The phase modulator includes a detection unit and a modulation unit. The detection unit is used to detect the interference fringe information generated after the combination of the first coherent light 10 and the second coherent light 20. The modulation unit is used to modulate the optical path difference between the first coherent light 10 and the second coherent light 20 according to the interference fringe information collected by the detection unit. The detection unit includes a light combining unit and a collection unit. The light combining unit is disposed on the optical paths of the first coherent light 10 and the second coherent light 20 and is used to combine the first coherent light 10 and the second coherent light 20 to form interference fringe information. The collection unit is used to detect the interference fringe information.

[0044] The above phase modulator can adopt existing phase modulation devices and be applied to this solution. For the sake of saving space, it will not be elaborated here. Through the above settings, the phase modulator can collect the interference fringes generated by the interference of the first coherent light 10 and the second coherent light 20 and feedback them to one of the light beams in real time (it can be the first coherent light 10 or the second coherent light 20). By modulating the optical path difference between the first coherent light 10 and the second coherent light 20 with the phase modulator, it can be ensured that the interference fringes can maintain their inherent phase under the disturbance in the exposure environment, preventing the interference fringes from having a large drift, so as to achieve the effect of reducing stray light.

[0045] The following describes the detailed process of preparing a grating by the above grating preparation device 100:

[0046] First, a grating substrate 91 is placed on the exposure plane 60 of the carrier stage 30. The grating substrate 91 is a substrate coated with a photosensitive material. Among them, the photosensitive material can be photosensitive resin, U glue or photoresist and other materials, and the substrate can be a silicon wafer, a glass or a quartz material sheet. The first coherent light 10 and the second coherent light 20 meet on the exposure plane 60 and produce an interference effect, thereby generating interference fringes. The phase and light intensity of the interference fringes are recorded by the photosensitive material. At the same time, the interference fringes are also collected by the phase modulator and feedback to one of the light beams in real time (it can be the first coherent light 10 or the second coherent light 20). By modulating the optical path difference between the first coherent light 10 and the second coherent light 20 with the phase modulator, it can be ensured that the interference fringes can maintain their inherent phase under the disturbance in the exposure environment, preventing the interference fringes from having a large drift. After exposure for a period of time t, and then through processes such as development and cleaning, a holographic grating in the exposure plane 60 can be obtained.

[0047] In addition to carrying the carrier stage 30 and the grating substrate 91, the motion mechanism 40 can also move along Figure 1Translation: Translational motion in the first direction Z, the second direction X, and the third direction Y as shown. Generally, the translational motions in the second direction X and the third direction Y are only for exposing different regions within the grating substrate 91 to achieve in-plane splicing of the holographic grating, but the exposure can only be performed after the movement ends. Through the above translations and phase locking, and the photosensitive material of the grating substrate 91 at any position is only irradiated within the exposure time t. Although a certain quality of grating lines and grating periods can be obtained as a whole, the high-frequency error after the combination of the first coherent light 10 and the second coherent light 20 is not effectively modulated. This high-frequency error stems from various lens combinations used in the optical path system that will increase unnecessary aberrations, as well as the speckle characteristics of the laser beam. This will lead to various defects in the prepared holographic grating, such as groove type errors of the grating at the microscopic level, bending of the grating lines on the sidewalls of the grating, and surface roughness, etc. These defects will cause the generation of stray light in the grating, thereby reducing the image resolution.

[0048] Translation: Therefore, to solve the above problems, the grating preparation device 100 of this embodiment is further provided with a first-direction motion mechanism 50. The first-direction motion mechanism 50 can vibrate the grating substrate 91 at a certain frequency in the first direction Z, so that the exposure plane 60 performs up and down micro-displacement motion in the first direction Z. As Figure 2 Translation: shown in the three positions of the exposure plane 60, where the first displacement position is the downward displacement of the first-direction motion mechanism 50 along the first direction Z, and then it returns to the reference position (which can be based on the exposure plane 60), and then performs the upward micro-displacement of the second displacement position, and then returns to the reference position again. Therefore, within the exposure time t, when the frequency of the first-direction motion mechanism 50 is m, the number of its motion scans is t / m times. It is equivalent to the photosensitive material within the exposure plane 60 being irradiated t / m times. The phase and light intensity within the light field at a certain position under one irradiation are fixed, but due to the scanning motion of the first-direction motion mechanism 50, the photosensitive material within the exposure plane 60 can be exposed to the light field multiple times along the second direction X.

[0049] Translation: As Figure 5 Translation: shown in the equivalent light intensity distribution diagram of the second direction X, this will cause the grating in this direction to be photosensitively homogenized. In this way, after exposure and development, the topography error of the grating groove (i.e., the grating microstructure 93 mentioned above) will be reduced. At the same time, due to the photosensitive homogenization in the sidewall direction, its roughness can also be significantly reduced. Furthermore, through this micro-displacement scanning motion method in the first direction Z, a low stray light grating with small grating groove type error and low roughness can be fabricated.

[0050] Translation: Taking Figure 1Taking the interference exposure system at a certain position shown in the embodiment as an example, where θ1 is the angle formed by the first coherent light 10 and the central axis of the converging exposure light field, and the central axis can be defined as the line in the exposure field with equal distances from the first coherent light 10 and the second coherent light 20, and θ2 is the angle formed by the second coherent light 20 and the central axis of the converging exposure light field. As a specific example, in this embodiment, θ1 = 30°, θ2 = 20°. According to the optical path difference between the first coherent light 10 and the second coherent light 20 at the exposure center position, the micro-displacement d of the moving mechanism 40 along the first direction Z can be calculated as 578 nm. Please refer to Figure 6 , through the optical path difference a - b = λ / 10 between the first coherent light 10 and the first coherent light 10, where λ is the wavelength of the coherent light, the displacement can be calculated as follows:

[0051]

[0052] Please refer to Figure 2 , from which the distances between the moving mechanism 40 at the reference position and the first displacement position and the second displacement position can be determined to be 578 nm respectively. Setting its scanning frequency to 1 / 10 and assuming the exposure time is 100 s, it is required that the micro-displacement motion device needs to achieve 1000 scanning motions within 100 s, which is equivalent to a certain position of the photosensitive material undergoing 1000 fixed-phase modulations within 100 s. Its grating line error and roughness can be greatly reduced through these 1000 homogenization motions, thereby achieving the homogenization of the grating. As Figure 4 shown in the schematic diagram of the morphology of the straight grating 97, after the incident light is incident, only the diffraction lights of levels T0 and T1 will be generated, and no additional stray light will be generated. Therefore, the above-mentioned straight grating 97 meets the standard requirements of a low-stray-light holographic grating.

[0053] Please also refer to Figure 1 and Figure 3 , Figure 3 The difference between the embodiment shown in Figure 1 and the embodiment shown in Figure 3 is that in the embodiment shown in Figure 3 , in addition to being able to move along the first direction Z, the second direction X, and the third direction Y, the carrier table 30 and the grating substrate 91 can also rotate around the central axis 95 following the moving mechanism 40 to achieve the pose adjustment of the exposure plane 60. Through Figure 7The shown blazed grating 96 has the following specific process: θ1 is the angle formed by the first coherent light 10 and the central axis of the exposure light field (i.e., the normal line O of the carrier 30) converging at the center position. The central axis (i.e., the normal line O of the carrier 30) can be defined as the line in the exposure field that is equidistant from the first coherent light 10 and the second coherent light 20. θ2 is the angle formed by the second coherent light 20 and the central axis of the exposure light field (i.e., the normal line O of the carrier 30) converging at the center position. Among them, θ1 = 60° and θ2 = 30°. According to the optical path difference between the first coherent light 10 and the second coherent light 20 at the exposure center position, the micro-displacement of the moving mechanism 40 along the first direction Z can be calculated to be 87 nm. Thus, it can be determined that the sum of the distances between the moving mechanism 40 at the reference position (see Figure 2 ) and the first displacement position and the second displacement position is 87 nm. Set its scanning frequency to 1 / 10. Assuming the exposure time is 100 s, it is required that the moving mechanism 50 in the first direction needs to achieve 1000 scanning movements within 100 s, which is equivalent to a certain position of the photosensitive material undergoing 1000 fixed phase modulations within 100 s. Its grating line error and roughness can be greatly reduced through these 1000 homogenization movements, thereby achieving the homogenization of the grating. As shown in Figure 7 the schematic diagram of the morphology of the blazed grating 96. After the incident light is incident, only the diffracted light of levels T0 and T1 will be generated, and no additional stray light will be generated. Therefore, the above blazed grating 96 meets the standard requirements of a low stray light holographic grating.

[0054] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. And these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A grating preparation device, characterized in that, The grating preparation device is used to expose a grating substrate to form a grating, and the grating preparation device includes: A light source module, configured to emit a first coherent light and a second coherent light; a carrying platform for carrying the grating substrate, wherein the first coherent light and the second coherent light interfere with each other on the grating substrate to form an interference exposure field, so as to expose the grating substrate; and A motion mechanism is connected to the supporting platform, and the motion mechanism includes a first direction motion mechanism, which is used to drive the supporting platform to reciprocate between a first position and a second position along a first direction, and the first direction is consistent with the normal direction of the supporting platform.

2. The grating preparation device according to claim 1, wherein The grating preparation device further includes a phase modulator, which is electrically connected to the light source module and is used to adjust the optical path difference between the first coherent light and the second coherent light.

3. The grating manufacturing apparatus according to claim 2, wherein The phase modulator includes a detection unit and a modulation unit. The detection unit is used to detect the interference fringe information generated after the first coherent light and the second coherent light are combined. The modulation unit is used to modulate the optical path difference between the first coherent light and the second coherent light according to the interference fringe information collected by the detection unit.

4. The grating preparation device according to claim 3, wherein The detection unit includes a light combining unit and a detection unit. The light combining unit is arranged on the optical path of the first coherent light and the second coherent light, and is used to combine the first coherent light and the second coherent light to form the interference fringe information. The detection unit is used to detect the interference fringe information.

5. The grating preparation device according to claim 1, characterized in that, The distance between the first position and the second position along the first direction is greater than or equal to 90 nm and less than or equal to 110 nm.

6. The grating preparation device according to claim 1, characterized in that, The grating preparation equipment also includes a mask, which is arranged on the light output path of the light source module, and the mask is arranged between the light source module and the supporting platform. The distance range between the mask and the surface of the grating substrate facing away from the supporting platform in the first direction is: greater than or equal to 10μm and less than or equal to 1000μm.

7. The grating preparation device according to claim 1, characterized in that, The first direction motion mechanism includes at least one of a piezoelectric inertial ceramic, an acousto-optic modulator or an electro-optic modulator.

8. The grating preparation device according to claim 1, wherein, The carrier platform has a central axis; the motion mechanism also includes a rotating mechanism, which is connected to the carrier platform and is used to drive the carrier platform to rotate around the central axis or reciprocate around the central axis between a third position and a fourth position to change the angle between the first coherent light and the second coherent light and the central axis of the interference exposure field.

9. The grating preparation device according to claim 1, characterized in that, The motion mechanism also includes a second direction translation mechanism, which is used to drive the carrier to translate along the second direction to achieve splicing of multiple interference exposure fields in the second direction. The second direction is consistent with the extension direction of the plane where the grating substrate is located when it is on the carrier.

10. The grating preparation device according to claim 9, characterized in that, The motion mechanism further includes a third-direction translation mechanism, which is used to drive the carrier table to translate in the third direction so as to realize the splicing of a plurality of the interference exposure fields in the third direction. The third direction is consistent with the extension direction of the plane where the grating substrate is located on the carrier table, and intersects or is perpendicular to the second direction.

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