Wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle constraint

Abstract

The application discloses a wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle restriction, and the method can solve the problem that some medium materials corresponding to the refractive index do not exist, so as to meet the needs of subsequent gradient refractive index matching, by selecting two medium materials with different refractive indexes and respectively controlling the thickness of the medium layers, and converting the medium layers into equivalent medium layers with different equivalent refractive indexes and equivalent thicknesses according to a transmission matrix. In addition, the change of the propagation phase is restricted by limiting the propagation angle of the incident light in the medium layer, so as to realize the insensitivity of the propagation phase to the angle change, meet the needs of wide-angle transmission enhancement, and determine the medium material corresponding to the refractive index according to the range of the propagation angle restriction. According to the above method, the medium material capable of realizing the wide-angle optical antireflection can be quickly selected, and the time cost required for selecting the medium material is greatly shortened.

Description

Technical Field

[0001] This invention belongs to the field of optical transparent devices, and more specifically, relates to a wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint. Background Technology

[0002] Optical substrates play a crucial role in imaging and detection systems. On one hand, they isolate the system from the external environment, protecting it; on the other hand, their transparency ensures the smooth transmission of light signals to the sensing elements, making them a key component for imaging and detection. With the development of imaging and detection technologies, the requirements for optical substrates are becoming increasingly stringent. They must not only possess excellent stability to withstand harsh environments but also have high optical transparency to ensure high transmission of incident light across a wide wavelength and angle range, meeting the needs of imaging and detection systems for full utilization of incident energy.

[0003] The transparency requirements of imaging systems are mainly concentrated in the visible 0.4-0.7 μm band, while those of detection systems are mainly concentrated in the 3-5 μm and 8-12 μm bands. Therefore, optical substrates need to have a wide transmission band. Chalcogenide glass, zinc sulfide, zinc selenide, or germanium are commonly chosen as optical substrates to meet the optical performance requirements of both imaging and detection systems. However, these optical substrates can achieve relatively low transmittance; for example, zinc sulfide has a transmittance of 86% in the 1-12 μm band, which is insufficient to fully utilize incident energy. Furthermore, the lack of a protective layer on the outside of the optical substrate exposes it to harsh environmental factors.

[0004] With the development of thin-film antireflection theory, depositing dielectric layers on optical substrates can not only serve as antireflective coatings to reduce reflection and enhance the transmission of the optical substrate, but also as protective films to isolate the optical substrate from the external environment and ensure the stability of its performance. Therefore, designing multilayer dielectric composite structures on optical substrates is one of the effective ways to ensure the stability of optical substrate performance and achieve enhanced transmission.

[0005] 1. Patent 201810009762.6 "An optical infrared antireflection film on a 3-12μm ZnS substrate and its preparation method" describes a method for preparing a three-layer infrared antireflection film sequentially deposited on an optical substrate ZnS, which increases the transmittance of the optical substrate in the 3-12μm range to 89% or higher.

[0006] 2. Patent 201210426609.6, “A Gradient Refractive Index Antireflective Film for Crystalline Silicon Solar Cells and Its Preparation Method,” describes a method for preparing three layers of gradient refractive index antireflective films sequentially deposited on a silicon substrate of a crystalline silicon solar cell, which can reduce the reflectivity of the silicon substrate in the 400-1200nm range to below 5%.

[0007] 3. Wang Daxing et al. from Changchun University of Science and Technology reported a method for preparing an infrared antireflection protective film deposited on a magnesium fluoride substrate. By repeatedly depositing H4-MgF2 periodic structures on the magnesium fluoride substrate and finally depositing a SiO2 dielectric layer on the outermost side of the film, the transmittance of the magnesium fluoride substrate at 3-5 μm can be increased to over 95%, and the composite structure can be isolated from the external environment, thus providing protection. (Wang Daxing et al., "Research and Preparation of 3-5 μm Infrared Antireflection Protective Film on Magnesium Fluoride Substrate").

[0008] 4. Huang Hongyu et al. from Changchun University of Science and Technology reported a method for preparing an infrared antireflection protective film deposited on a chalcogenide glass substrate. By depositing Ge, ZnS, and YbF3 thin films with matching refractive indices as high, medium, and low refractive index materials on the chalcogenide glass substrate, the transmittance of the chalcogenide glass substrate in the 8-12 μm range can be increased to 91.1%, and the film exhibits good moisture resistance, high hardness, and robust film reliability, meeting the expected performance requirements. (Huang Hongyu et al., "Development of High-Strength Moisture-Proof Infrared Antireflection and Protective Film for Chalcogenide Glass Substrate").

[0009] In summary, the main shortcomings of existing technologies are:

[0010] 1. Failure to consider the need for wide-angle incident light transmission enhancement: The aforementioned optical substrates only consider achieving high transmission within a specific wide wavelength range, and the designed optical substrate anti-reflection composite structures only consider improving transmittance over a wide wavelength range. Neither approach has tested transmission results in the wide-angle range, thus failing to meet the requirement of fully utilizing incident energy. Therefore, there is an urgent need to find a design method for optical substrate anti-reflection composite structures that can improve transmittance over a wide angle range.

[0011] 2. Difficulty in Achieving Broad-Band Transmission Enhancement: Imaging and detection systems require optically transparent devices with high transparency in the visible band, 3-5μm, and 8-12μm. However, the aforementioned optical substrates and the designed anti-reflection composite structures can only achieve transmission enhancement in specific bands, which is insufficient to meet the need for broad-band transmission enhancement. Therefore, there is an urgent need to find a design method for anti-reflection composite structures of optical substrates that can improve broad-band transmittance.

[0012] 3. Lack of Design Principles and Methods for Optical Substrate Anti-reflection Composite Structures: Existing methods for enhancing the transmission of optical substrates mainly focus on fabrication processes. Depositing a dielectric layer structure with given parameters on the optical substrate can only achieve transmission enhancement for a specific optical substrate. Furthermore, the aforementioned fabrication processes only provide the relevant parameters of the dielectric layer without specific implementation principles and design methods, making it difficult to design corresponding optical substrate anti-reflection composite structures for arbitrary optical substrates. Therefore, there is an urgent need to find a design method for obtaining corresponding optical substrate anti-reflection composite structures based on a given optical substrate.

[0013] 4. Lack of materials with corresponding refractive indices to meet the requirements of gradient refractive index matching: The design of antireflective composite structures for optical substrates typically uses gradient refractive indices to meet matching conditions. However, due to practical limitations during the design and fabrication process, it is often difficult to find media materials with corresponding refractive indices, thus failing to meet the requirements of gradient refractive index matching and making it difficult to achieve transmission enhancement across a wide wavelength and wide angle domain for the optical substrate. Therefore, there is an urgent need to find an equivalent refractive index design method that can solve the problem of the lack of materials with corresponding actual refractive indices.

[0014] In view of this, the present invention is proposed. Summary of the Invention

[0015] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint, which solves the problems mentioned in the background art.

[0016] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0017] A wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint is proposed. To achieve wide-angle optical anti-reflection in the visible (0.4-0.7 μm) and infrared (1-12 μm) ranges from -45° to 45°, the method selects the appropriate dielectric layer material by limiting the propagation angle to constrain the change in propagation phase, thus satisfying the phase angle constraint condition for wide-angle optical anti-reflection. Then, by sequentially depositing dielectric layers with decreasing refractive indices on the optical substrate, the total equivalent admittance is brought close to 1, satisfying the gradient refractive index matching condition for wide-angle optical anti-reflection. For non-existent refractive indices, equivalent refractive indices are used as substitutes. By constructing a series of equivalent dielectric layers with decreasing equivalent refractive index gradients, the equivalent gradient refractive index matching condition for wide-angle optical anti-reflection is satisfied. The specific method is as follows, with the following steps:

[0018] I. Select two media materials with different refractive indices as media layer A and media layer B. The refractive indices of media layer A and media layer B are n1 and n2, respectively, and the thicknesses are d1 and d2, respectively.

[0019] II. Based on the refractive indices of dielectric layer A and dielectric layer B, through and Calculate the reflection and transmission coefficients of each interface, and construct the interface interaction matrix I from the reflection and transmission coefficients. k-1，k Its expression is: Where n k-1 and n k These are the refractive indices of two adjacent layers;

[0020] III. Based on the thickness determined in step I, through Calculate the propagation phase in each dielectric layer and construct the propagation matrix of the dielectric layer. Where, n k Let d be the refractive index of the dielectric layer. k Where λ is the thickness of the dielectric layer, and λ is the wavelength designed for anti-reflection.

[0021] IV. Multiply the interface interaction matrix and the propagation matrix sequentially to obtain the total transfer matrix S of the entire multilayer dielectric structure, which is expressed as: S = I 01 L1I 12 L2I 23 ;

[0022] V. Based on the total transfer matrix calculated in step IV, let the total transfer matrix of dielectric layer A and dielectric layer B be equal to the transfer matrix S = I' of a single-layer dielectric. 01 L'1I' 12 Determine the equivalent refractive index n of the equivalent medium layer. i and equivalent thickness d i ;

[0023] VI. By adjusting the thicknesses d1 and d2 of the two initial media, a series of media layers with decreasing equivalent refractive index are generated, forming an equivalent media gradient layer that meets the gradient refractive index matching condition.

[0024] VII. The equivalent refractive index gradient layer generated in step VI is deposited sequentially on the optical substrate in order of decreasing refractive index, ultimately forming an optical antireflection composite structure with decreasing gradient refractive index.

[0025] Optionally, the optical substrate may include, but is not limited to, magnesium fluoride, zinc sulfide, zinc selenide, silicon, and germanium.

[0026] Optionally, the optical antireflection composite structure is composed of dielectric layer A and dielectric layer B, and the design of the equivalent dielectric layer is achieved by controlling the thickness of dielectric layer A and dielectric layer B.

[0027] Optionally, the materials of dielectric layer A and dielectric layer B include, but are not limited to, one of TiO2 and YbF3.

[0028] Optionally, the equivalent refractive index n obtained in step V i A value greater than or equal to 1.7 is used to achieve transmission enhancement over a wide angle range, and the equivalent refractive index n i ≥1.7 can constrain the propagation phase by limiting the propagation angle to within 25°, thereby achieving transmission enhancement of the optical substrate antireflection composite structure in a wide-angle domain.

[0029] Optionally, to reduce the equivalent admittance, the admittance of the optical substrate is set to α+iβ, where α is the real part of the optical substrate admittance and β is the imaginary part of the optical substrate admittance;

[0030] Combining optical substrate admittance α+iβ and dielectric layer admittance m i Calculate the total equivalent admittance x+iy of the optical substrate antireflection composite structure, which satisfies the following relationship in δ i Let x be the propagation phase in the medium, and y be the real and imaginary parts of the equivalent admittance, respectively; m i The admittance of the dielectric material;

[0031] By selecting a medium material with decreasing refractive index and adjusting the thickness of each layer, the total equivalent admittance x+iy is made close to 1, satisfying the following condition x+iy≈1, where the total admittance is matched with the air admittance to minimize reflection and enhance transmission.

[0032] Under the above conditions, the optical anti-reflection composite structure of optical substrate is finally realized to achieve optical anti-reflection effect in a wide-angle range.

[0033] Optionally, a multilayer film system for achieving equivalent gradient refractive index matching has a total number of layers between 2 and 20 and a period between 1 and 10.

[0034] Optionally, for a non-existent refractive index of a medium, an equivalent refractive index can be used to replace the actual non-existent refractive index of the medium. This involves the following steps:

[0035] Choose a dielectric layer with a refractive index of n1 and a dielectric layer with a refractive index of n2, where the refractive indices of n1 and n2 are both within the range of the refractive index of air and the refractive index of the optical substrate.

[0036] By adjusting the thicknesses d1 and d2 of the two dielectric layers within a range of 300 nm, the propagation phase of light in the two dielectric layers can be adjusted to achieve combinations of different equivalent refractive indices, thereby constructing an equivalent dielectric layer that meets the design requirements.

[0037] By adjusting the combination of refractive index and thickness of the two dielectric layers, a series of equivalent dielectric layers with progressively decreasing equivalent refractive index are generated, thereby satisfying the gradient refractive index matching condition and achieving admittance matching between the optical substrate and air.

[0038] Furthermore, this invention obtains an interaction matrix by selecting a dielectric layer with refractive index n1 and a dielectric layer with refractive index n2, calculating the reflection and transmission coefficients of the corresponding interfaces, and obtaining the propagation matrix based on the thicknesses of dielectric layers A and B. Multiplying the interaction matrix and the propagation matrix yields the total transfer matrix. Setting the total transfer matrix equal to the transfer matrix of a single-layer dielectric layer yields the equivalent refractive index and equivalent thickness of the equivalent dielectric layer. A series of equivalent dielectric layers are obtained by changing the thicknesses of dielectric layers A and B. The range of equivalent refractive indices is limited to restrict changes in the propagation phase, thereby satisfying the phase angle constraint condition for wide-angle optical anti-reflection. The equivalent dielectric layers are superimposed on the optical substrate in a gradient decreasing from large to small equivalent refractive index, satisfying the equivalent gradient refractive index matching condition for wide-angle optical anti-reflection. This wide-angle optical anti-reflection method can design corresponding optical substrate anti-reflection composite structures based on a given optical substrate to achieve wide-angle optical anti-reflection in the visible 0.4-0.7μm and infrared 1-12μm ranges from -45° to 45°. Furthermore, by using an equivalent refractive index to replace a non-existent refractive index, the refractive index gradient can be made smoother, thereby further improving the wide-angle transmittance of the optical substrate.

[0039] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all of the following advantages at the same time:

[0040] 1. This invention proposes a method for selecting dielectric materials for wide-angle optical transmission enhancement based on phase angle constraints. By limiting the propagation angle of incident light in the dielectric layer to constrain the change in propagation phase, the propagation phase becomes insensitive to angle changes, meeting the requirements for wide-angle transmission enhancement. Furthermore, the range of the propagation angle constraint allows for the determination of the dielectric material with the corresponding refractive index. This method enables the rapid selection of dielectric materials capable of achieving wide-angle optical transmission enhancement, significantly reducing the time cost required for material selection.

[0041] 2. This invention proposes a method for designing the equivalent refractive index and equivalent thickness of an equivalent dielectric layer. By selecting two dielectric materials with different refractive indices and controlling the thickness of the dielectric layer separately, it is possible to transform them into equivalent dielectric layers with different equivalent refractive indices and equivalent thicknesses according to the transfer matrix. This solves the problem that some dielectric materials corresponding to certain refractive indices are currently unavailable, thus meeting the requirements for subsequent gradient refractive index matching.

[0042] 3. This invention proposes a design method for an optical substrate anti-reflection composite structure based on equivalent gradient refractive index matching. By depositing a series of equivalent dielectric layers satisfying equivalent gradient refractive index matching on the optical substrate, the equivalent admittance of the optical substrate anti-reflection composite structure is reduced to 1, satisfying the condition of matching with air admittance, thereby achieving transmission enhancement in a wide-band, wide-angle domain. Based on the above method, the relevant parameters of the required equivalent dielectric layers can be obtained, thus yielding the corresponding optical substrate anti-reflection composite structure to achieve wide-angle optical transmission enhancement.

[0043] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0044] The accompanying drawings described below are merely some embodiments. Those skilled in the art can obtain other drawings based on these drawings without any creative effort. In the drawings:

[0045] Figure 1 This is a schematic diagram illustrating the wide-angle domain anti-reflection achieved by controlling the equivalent refractive index to constrain the propagation angle, as described in this invention.

[0046] Figure 2 This is a schematic diagram illustrating the reduction of optical substrate admittance achieved by employing gradient refractive index matching as described in this invention.

[0047] Figure 3 This is one of the schematic diagrams illustrating the equivalent dielectric layer design achieved by controlling the thickness of dielectric layer A and dielectric layer B according to the present invention.

[0048] Figure 4 This is a schematic diagram of the optical substrate antireflection composite structure designed in the visible 0.4-0.7μm and infrared 1-12μm bands as described in this invention.

[0049] Figure 5 This is a schematic diagram of the admittance of the optical substrate antireflection composite structure designed in the visible 0.4-0.7μm and infrared 1-12μm bands as described in this invention.

[0050] Figure 6 This is a schematic diagram of the transmittance of the optical substrate antireflection composite structure designed in the visible 0.4-0.7μm and infrared 1-12μm bands as described in this invention.

[0051] Figure 7 This is the second schematic diagram of the wide-angle domain anti-reflection achieved by controlling the equivalent refractive index to constrain the propagation angle as described in this invention.

[0052] The attached diagram lists the components represented by each number as follows:

[0053] 1. Dielectric layer A; 2. Dielectric layer B; 3. Equivalent dielectric layer; 4. TiO2 dielectric layer; 5. YbF3 dielectric layer; 6. ZnS optical substrate.

[0054] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0055] The invention will now be described in further detail with reference to the accompanying drawings.

[0056] Please see Figures 1-7 As shown, this embodiment provides a wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint. To achieve wide-angle optical anti-reflection in the visible light band (0.4-0.7 μm) and the infrared band (1-12 μm) within the range of -45° to 45°, the method includes the following steps:

[0057] I. Select two dielectric materials with different refractive indices as dielectric layer A1 and dielectric layer B2. The refractive indices of dielectric layer A1 and dielectric layer B2 are n1 and n2, respectively, and the thicknesses are d1 and d2, respectively.

[0058] II. Based on the refractive indices of dielectric layer A1 and dielectric layer B2, through and Calculate the reflection and transmission coefficients of each interface, and construct the interface interaction matrix I from the reflection and transmission coefficients. k-1，k Its expression is: Where n k-1 and n k These are the refractive indices of two adjacent layers;

[0059] III. Based on the thickness determined in step I, through Calculate the propagation phase in each dielectric layer and construct the propagation matrix of the dielectric layer. Where, n k Let d be the refractive index of the dielectric layer. k Where λ is the thickness of the dielectric layer, and λ is the wavelength designed for anti-reflection.

[0060] IV. Multiply the interface interaction matrix and the propagation matrix sequentially to obtain the total transfer matrix S of the entire multilayer dielectric structure, which is expressed as: S = I 01 L1I 12 L2I 23 ;

[0061] V. Based on the total transfer matrix calculated in step IV, let the total transfer matrix of dielectric layer A1 and dielectric layer B2 be equal to the transfer matrix S = I' of a single-layer dielectric. 01 L'1I'12 Determine the equivalent refractive index n of the equivalent dielectric layer 3. i and equivalent thickness d i ;

[0062] VI. By adjusting the thicknesses d1 and d2 of the two initial media, a series of media layers with decreasing equivalent refractive index are generated, forming an equivalent media gradient layer that meets the gradient refractive index matching condition.

[0063] VII. The equivalent refractive index gradient layer generated in step VI is deposited sequentially on the optical substrate in order of decreasing refractive index, ultimately forming an optical antireflection composite structure with decreasing gradient refractive index.

[0064] In this embodiment, the optical substrate includes, but is not limited to, magnesium fluoride, zinc sulfide, zinc selenide, silicon, and germanium.

[0065] In this embodiment, the optical antireflection composite structure is composed of dielectric layer A1 and dielectric layer B2, and the design of the equivalent dielectric layer 3 is achieved by controlling the thickness of dielectric layer A1 and dielectric layer B2.

[0066] In this embodiment, the materials of dielectric layer A1 and dielectric layer B2 include, but are not limited to, one of TiO2 and YbF3.

[0067] In this embodiment, the equivalent refractive index n obtained in step V is... i A value greater than or equal to 1.7 is used to achieve transmission enhancement over a wide angle range, and the equivalent refractive index n i ≥1.7 can constrain the propagation phase by limiting the propagation angle to within 25°, thereby achieving transmission enhancement of the optical substrate antireflection composite structure in a wide-angle domain.

[0068] In this embodiment, to reduce the equivalent admittance, the admittance of the optical substrate is set to α+iβ, where α is the real part of the optical substrate admittance and β is the imaginary part of the optical substrate admittance.

[0069] Combining optical substrate admittance α+iβ and dielectric layer admittance m i Calculate the total equivalent admittance x+iy of the optical substrate antireflection composite structure, which satisfies the following relationship in δ i Let x be the propagation phase in the medium, and y be the real and imaginary parts of the equivalent admittance, respectively; m i Let be the admittance of the dielectric material. According to the above formula, by using a series of dielectric materials with a decreasing refractive index in the range of optical substrate and air refractive index, the equivalent admittance of the optical substrate antireflection composite structure can be reduced to 1 to meet the condition of matching the air admittance, thereby realizing optical antireflection in the wide-angle domain.

[0070] By selecting a medium material with decreasing refractive index and adjusting the thickness of each layer, the total equivalent admittance x + iy is made close to 1, satisfying the condition x + iy ≈ 1. Here, the total admittance is matched with the air admittance to minimize reflection and enhance transmission. Air admittance is a quantification of the characteristics of electromagnetic wave transmission in free space or air, typically normalized to 1, and used as a benchmark for admittance matching in optical systems. In anti-reflection design, enhancing light transmission can be achieved by gradually approaching the air admittance through adjusting the material's admittance.

[0071] Under the above conditions, the optical anti-reflection composite structure of optical substrate is finally realized to achieve optical anti-reflection effect in a wide-angle range.

[0072] In this embodiment, the multilayer film system used to achieve equivalent gradient refractive index matching has a total number of layers between 2 and 20 and a period between 1 and 10.

[0073] In this embodiment, for a non-existent medium refractive index, an equivalent refractive index can be used to replace the actual non-existent medium refractive index. Specifically, this includes the following steps:

[0074] Choose a dielectric layer with a refractive index of n1 and a dielectric layer with a refractive index of n2, where the refractive indices of n1 and n2 are both within the range of the refractive index of air and the refractive index of the optical substrate.

[0075] By adjusting the thicknesses d1 and d2 of the two dielectric layers within a range of 300 nm, the propagation phase of light in the two dielectric layers can be adjusted to achieve combinations of different equivalent refractive indices, thereby constructing an equivalent dielectric layer 3 that meets the design requirements.

[0076] By adjusting the combination of refractive index and thickness of the two dielectric layers, a series of equivalent dielectric layers 3 with gradually decreasing equivalent refractive index are generated, thereby satisfying the gradient refractive index matching condition and realizing admittance matching between the optical substrate and air.

[0077] Depend on Figure 1 As shown, by controlling the equivalent refractive index to be greater than or equal to 1.7, the propagation angle of the incident light in the equivalent medium layer 3 can be constrained within the range of 25°, thereby limiting the change of the propagation phase with the incident angle, so as to meet the phase angle constraint condition of wide-angle optical transmission enhancement and realize wide-angle transmission enhancement.

[0078] Depend on Figure 2 As shown, by depositing dielectric layers with successively decreasing refractive indices on an optical substrate and controlling the thickness of the dielectric layers, the equivalent admittance of the optical substrate can be reduced to around 1, thereby satisfying the condition of matching the air admittance and realizing the anti-reflection and anti-reflection of the optical substrate.

[0079] Depend on Figure 3As shown, a dielectric layer A1 with a refractive index of n1 and a dielectric layer B2 with a refractive index of n2 are selected. The thicknesses d1 and d2 of the two dielectric layers are controlled. By calculating the transfer matrix, they can be transformed into a new equivalent dielectric layer 3, thereby obtaining a new equivalent refractive index ni and equivalent thickness di.

[0080] Experimental example: A five-period TiO2 / YbF3 composite structure was used to achieve optical substrate antireflection in the visible 0.4-0.7μm and infrared 1-12μm bands. Here, 4 represents the dielectric TiO2, 5 represents the dielectric YbF3, and 6 represents the optical substrate, which is ZnS. The thicknesses of the deposited layers from top to bottom are as follows: the first TiO2 layer is 15-25 nm thick; the second YbF3 layer is 175-185 nm thick; the third TiO2 layer is 90-100 nm thick; the fourth YbF3 layer is 165-175 nm thick; the fifth TiO2 layer is 75-85 nm thick; the sixth YbF3 layer is 140-150 nm thick; the seventh TiO2 layer is 85-95 nm thick; the eighth YbF3 layer is 140-150 nm thick; the ninth TiO2 layer is 80-90 nm thick; and the tenth YbF3 layer is 145-155 nm thick. Figure 4 ).

[0081] Simulation experiments were conducted on a five-period TiO2 / YbF3 composite structure. Figure 5 As shown in the simulation results, this optical substrate antireflection composite structure can reduce the admittance of the optical substrate from around 2.4 to around 1.49, significantly reducing the equivalent admittance of the optical substrate. This satisfies the condition of matching the air admittance, thus achieving antireflection and antireflection of the optical substrate. Furthermore, from the simulation results ( Figure 6 From the perspective of optical substrate antireflection composite structure, in the 0.4-0.7μm wavelength range, the original average transmittance of the optical substrate can be increased from 83% to 84.5%; in the 1-12μm wavelength range, the original average transmittance of the optical substrate can be increased from 86% to 93.5%. Furthermore, it maintains a stable and high transmittance over a wide angle range, thus achieving wide-angle transmission enhancement of the optical substrate.

[0082] This invention is not limited to the embodiments described above. Anyone should understand that structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention. Technical aspects, shapes, and structures not described in detail in this invention are all publicly known technologies.

Claims

1. A wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle constraint, for realizing wide-angle optical antireflection in the range of -45° to 45° in the visible light band 0.4-0.7 μm and the infrared band 1-12 μm, characterized in that, For a non-existent refractive index of a medium, an equivalent refractive index can be used to replace the actual non-existent refractive index. This involves the following steps: I. Select two medium materials with different refractive indexes as medium layer A (1) and medium layer B (2), the refractive indexes of medium layer A (1) and medium layer B (2) are and , and the thicknesses are and ; II. Based on the refractive indexes of the medium layer A (1) and the medium layer B (2), the reflection coefficient and the transmission coefficient of each interface are calculated, and the action matrix of the interface is constructed from the reflection coefficient and the transmission coefficient and The reflection coefficient and the transmission coefficient of each interface are calculated, and the action matrix of the interface is constructed from the reflection coefficient and the transmission coefficient The expression is: Where n k-1 and n k are the refractive indexes of the adjacent two layers respectively III. Based on the thickness determined in step I, the propagation phase in each medium layer is calculated and a propagation matrix of the medium layers is constructed wherein, is the refractive index of the medium layer, is the thickness of the medium layer, and λ is the wavelength for which the antireflection is designed;​ IV、The interface matrix and the propagation matrix are multiplied in sequence to obtain the total transfer matrix of the whole multilayer medium structure The expression is: ; V. calculating a total transfer matrix based on step IV, letting the total transfer matrix of the dielectric layer A (1) and the dielectric layer B (2) be equal to the transfer matrix of a single layer of dielectric , determining an equivalent refractive index and an equivalent thickness of the equivalent dielectric layer (3) VI、By adjusting the thickness of the medium layer A (1) and the medium layer B (2) and , a series of medium layers with decreasing equivalent refractive index are generated to form an equivalent medium gradient layer that meets the gradient refractive index matching condition; VII. The equivalent refractive index gradient layer generated in step VI is deposited sequentially on the optical substrate in order of decreasing refractive index, ultimately forming an optical anti-reflection composite structure with decreasing gradient refractive index. The equivalent refractive index obtained in the step V greater than or equal to 1.7 to achieve the transmission enhancement in a wide angle domain, and the equivalent refractive index ni≥1.7 can limit the propagation angle within 25° to constrain the propagation phase, so as to achieve the transmission enhancement of the optical substrate antireflection composite structure in a wide angle domain. To reduce the equivalent admittance, the admittance of the optical substrate is set to wherein is the real part of the optical substrate admittance, is the imaginary part of the optical substrate admittance; Combined optical substrate admittance and medium layer admittance , the total equivalent admittance of the optical substrate antireflection composite is calculated which satisfies the following relation where , is the propagation phase in the medium, and are the real and imaginary parts of the equivalent admittance, respectively; is the admittance of the medium material; By choosing dielectric materials of decreasing refractive index and adjusting the thickness of each layer, the total equivalent admittance Approaching 1, the following conditions are met where the total admittance matches the admittance of air to minimize reflection and enhance transmission.

2. The wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that, Optical substrates include one of magnesium fluoride, zinc sulfide, zinc selenide, silicon, and germanium.

3. The wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that, The materials of dielectric layer A (1) and dielectric layer B (2) are TiO2 and YbF3.

4. The wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that, Multilayer film systems used to achieve equivalent gradient refractive index matching have a total number of layers between 2 and 20 and a period between 1 and 10.

5. The wide-angle optical antireflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that, Includes the following steps: A medium layer having a refractive index of and a medium layer having a refractive index of are selected, wherein and the refractive indices of both are in the range between the refractive index of air and the refractive index of the optical substrate. By adjusting the thickness of the two dielectric layers and In the range of 300 nm, the phase of light propagation in the two layers of dielectric is adjusted to achieve the combination of different equivalent refractive indices, and the equivalent dielectric layer (3) that meets the design requirements is constructed; By adjusting the combination of refractive index and thickness of the two dielectric layers, a series of equivalent dielectric layers with gradually decreasing equivalent refractive index are generated (3), thereby satisfying the gradient refractive index matching condition and realizing admittance matching between the optical substrate and the air.

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