Multilayer optical film and method of making the same

Abstract

This invention provides a multi-wavelength thin film and its fabrication method. The thin film includes an optical substrate and at least one first stacked structure or at least two second stacked structures on the optical substrate. The at least one first stacked structure includes multiple sets of alternately stacked layers with different refractive indices, each set having a different optical thickness. An intercalation layer is disposed between the at least two second stacked structures. Each of the at least two second stacked structures includes multiple sets of alternately stacked layers with different refractive indices. The optical thickness of each set of layers in each second stacked structure is the same, and the optical thickness of the intercalation layer is the average of the optical thicknesses of the corresponding layers in adjacent second stacked structures. The thin film has multiple discrete target wavelengths, where the target wavelength is the reflection wavelength when the reflectivity of the thin film is greater than a predetermined threshold.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and more specifically to a multi-wavelength thin film and its preparation method. Background Technology

[0002] High-reflectivity coatings are stacked structures formed by alternating deposition of layers with different refractive indices. Each layer must have a certain optical thickness based on the center wavelength to achieve a reflectivity of over 99.9% at the center wavelength. However, single-wavelength stacked structures with limited bandwidth, as well as multi-wavelength high-reflectivity coatings formed by gluing or splicing single-wavelength stacked structures, have certain performance bottlenecks. Summary of the Invention

[0003] In view of the above problems, embodiments of the present invention provide a multi-wavelength thin film and a method for preparing the same.

[0004] According to a first aspect of the present invention, a multi-wavelength thin film is provided. The thin film includes an optical substrate and at least one first stacked structure or at least two second stacked structures on the optical substrate. The at least one first stacked structure includes multiple sets of alternately stacked film layers with different refractive indices, each set having a different optical thickness. An intercalation layer is disposed between the at least two second stacked structures, each of the at least two second stacked structures including multiple sets of alternately stacked film layers with different refractive indices, each set of film layers in each second stacked structure having the same optical thickness, and the optical thickness of the intercalation layer being the average of the optical thicknesses of the corresponding film layers in adjacent second stacked structures. The thin film has multiple discrete target wavelengths, the target wavelengths being the reflection wavelengths when the reflectivity of the thin film is greater than a predetermined threshold.

[0005] According to an embodiment of the present invention, the sum of the optical thicknesses of each film layer in each group of films in at least one first stacked structure is a first preset thickness, and the multiple discrete target wavelengths are in a multiple relationship. The first preset thickness represents half of the target wavelength corresponding to each first stacked structure.

[0006] According to an embodiment of the present invention, the thin film has a first target wavelength and a second target wavelength that are multiples of each other, and when the first target wavelength is twice the second target wavelength, the target wavelength corresponding to the first preset thickness is the first target wavelength, or the target wavelengths corresponding to the first preset thickness are the first target wavelength and the second target wavelength respectively.

[0007] According to an embodiment of the present invention, the optical thickness of each film layer in each group of films in at least one first stacked structure is k times the first preset thickness, wherein the value of k includes 0.25 to 0.75.

[0008] According to an embodiment of the present invention, the optical thickness of each film layer in each group of films in at least two second stacked structures is a second preset thickness, and the multiple discrete target wavelengths of the film are in a non-multiple relationship, the second preset thickness representing one-quarter of the target wavelength corresponding to each second stacked structure.

[0009] According to an embodiment of the present invention, when the thin film has a third target wavelength and a fourth target wavelength that are not multiples of each other, the target wavelengths corresponding to the second preset thickness are the third target wavelength and the fourth target wavelength, respectively, or the target wavelengths corresponding to the second preset thickness are the average of the third target wavelength and the fourth target wavelength.

[0010] According to an embodiment of the present invention, when the second preset thickness is the average of the third target wavelength and the fourth target wavelength, the number of each film layer in at least two second stacked structures is the same.

[0011] According to an embodiment of the present invention, the number of groups of each film layer in at least one first stacked structure and / or at least two second stacked structures is determined based on the reflectivity of at least one first stacked structure and / or at least two second stacked structures and the refractive index of each film layer in each group.

[0012] According to embodiments of the present invention, each group of film layers in at least one stacked structure includes a first film layer and a second film layer, and each group of film layers in at least two stacked structures includes a third film layer and a fourth film layer; the first film layer, the third film layer and the insertion layer include at least one of Ta2O5, TiO2, ZnS and HfO2; the second film layer and the fourth film layer include at least one of SiO2, Al2O3 and YbF3.

[0013] According to a second aspect of the present invention, a method for fabricating a multi-wavelength thin film is provided. The method includes: determining film layer parameters for at least one first stacked structure or at least two second stacked structures; the at least one first stacked structure comprising alternatingly stacked multiple sets of film layers with different refractive indices, each set of film layers having a different optical thickness; an insertion layer disposed between at least two second stacked structures, each of the at least two second stacked structures comprising alternatingly stacked multiple sets of film layers with different refractive indices, each set of film layers having the same optical thickness, the optical thickness of the insertion layer being the average of the optical thicknesses of the corresponding film layers of adjacent second stacked structures; the film layer parameters include the optical thickness of each film layer and the number of sets. At least one first stacked structure or at least two second stacked structures are formed on an optical substrate based on the film layer parameters; the thin film has multiple discrete target wavelengths, the target wavelength being the reflection wavelength when the reflectivity of the thin film is greater than a predetermined threshold.

[0014] According to embodiments of the present invention, a multi-wavelength thin film is provided. This thin film forms multiple discrete target wavelengths by depositing at least one first stacked structure or at least two second stacked structures on an optical substrate. The first and second stacked structures do not rely on conventional quarter-wavelength periodic stacking, and an intercalation layer is provided between the second stacked structures. This not only meets the application requirements for multiple target wavelengths but also avoids the additional interface losses, thermal deformation misalignment, and structural complexity problems caused by gluing or splicing single-wavelength stacked structures. Attached Figure Description

[0015] The above-described features, other objects, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0016] Figure 1 A schematic diagram of the structure of a multi-wavelength thin film according to an embodiment of the present invention is shown.

[0017] Figure 2 A schematic diagram of the structure of a multi-wavelength thin film according to another embodiment of the present invention is shown.

[0018] Figure 3 A schematic diagram of the structure of a multi-wavelength thin film according to another embodiment of the present invention is shown.

[0019] Figure 4 The reflectance spectrum of a multi-wavelength thin film according to an embodiment of the present invention is illustrated schematically.

[0020] Figure 5 The reflectance spectrum of a multi-wavelength thin film according to another embodiment of the present invention is illustrated schematically;

[0021] Figure 6 A flowchart illustrating a method for preparing a multi-wavelength thin film according to an embodiment of the present invention is shown schematically;

[0022] Figure 7 and Figure 8 The optimal film parameter distribution and transmission spectrum of the multi-wavelength thin films according to embodiments of the present invention are schematically shown respectively.

[0023] Figure 9 and Figure 10 The actual reflection spectrum and cross-sectional view of the multi-wavelength thin film according to an embodiment of the present invention are schematically shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0028] In the description of this invention, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the subsystem or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Similarly, to simplify the invention and aid in understanding one or more of the various disclosed aspects, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] High-reflectivity coatings in the visible infrared band typically employ a "quarter-wavelength cyclic stack" structure designed with the center wavelength λ0 as the baseline. The core construction logic of this structure involves alternating deposition of higher and lower refractive index layers onto an optical substrate, strictly controlling the optical thickness of each layer to satisfy n×d=λ0 / 4, where n is the refractive index of each layer and d is the physical thickness of each layer. By repeatedly depositing layers of different refractive indices for 8 to 50 cycles, a reflectivity of 99.9% to 99.9999% can be achieved at the center wavelength λ0. This characteristic makes it dominant in scenarios requiring high reflectivity at a single wavelength.

[0031] However, the aforementioned structure also suffers from insurmountable performance bottlenecks; the bandwidth of the target reflectivity (over 99.9% reflectivity) band is strictly limited by the refractive index difference between films with different refractive indices. The limiting bandwidth of the target reflectivity band must meet the following requirements.

[0032] (1)

[0033] In formula (1), Δω is the limiting bandwidth of the target reflectivity band, ω m The frequency of the center wavelength is n1, and n2 are the refractive indices of different refractive index films.

[0034] For high-reflectivity films prepared using conventional coating techniques such as ion beam sputtering, magnetron sputtering, and electron beam evaporation, the bandwidth of the target reflectivity can only reach 10% to 20% of the center wavelength λ0. More importantly, within this limited bandwidth, the spatial distribution of reflectivity is extremely uneven, often exhibiting orders of magnitude differences. For example, the transmittance at the center wavelength λ0 can be as low as below 1 ppm, while the reflectivity in regions deviating from the center wavelength λ0 decays rapidly, failing to meet the reflection requirements for wide-band or multi-wavelength applications.

[0035] With the rapid development of modern precision measurement technology, the application demand for multi-wavelength high-reflectivity films is experiencing explosive growth. In many application scenarios, such as quantum optics, multi-wavelength laser systems, and precision measurement, single-wavelength high-reflectivity films are no longer sufficient to meet the complex design requirements of optical systems, and the bandwidth limitations of traditional "quarter-wavelength circular stacking" structures are becoming increasingly apparent. Achieving multi-wavelength reflection by gluing or splicing single-wavelength stacked structures inevitably brings additional interface losses, thermal deformation mismatch, and structural complexity issues, becoming one of the key factors restricting technological progress in related fields.

[0036] In view of this, embodiments of the present invention provide a multi-wavelength thin film and its preparation method, which realizes the design of multi-wavelength optical thin films by breaking the traditional periodic structure, and solves the film thickness error problem in the preparation process by combining the reflection spectrum with the film thickness inversion method of scanning electron microscopy.

[0037] Figure 1 A schematic diagram of the structure of a multi-wavelength thin film according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of the structure of a multi-wavelength thin film according to another embodiment of the present invention is shown. Figure 3 A schematic diagram of the structure of a multi-wavelength thin film according to another embodiment of the present invention is shown.

[0038] like Figures 1-3 As shown, the multi-wavelength thin film of this embodiment may include an optical substrate 100 and a first stacked structure 110 or a second stacked structure 120 on the optical substrate 100. The optical substrate 100 may include Si, SiC, etc.

[0039] The first stacked structure 110 and the second stacked structure 120 may include multiple sets of alternating stacked film layers with different refractive indices. For example, the first stacked structure 110 may include multiple sets of first film layers 111 and second film layers 112 with different refractive indices; the second stacked structure 120 may include multiple sets of third film layers 121 and fourth film layers 122 with different refractive indices. The first film layer 111 and the third film layer 121 may include at least one of Ta2O5, TiO2, ZnS, and HfO2; the second film layer 112 and the fourth film layer 122 may include at least one of SiO2, Al2O3, and YbF3.

[0040] In some embodiments, such as Figure 1 and Figure 2 As shown, the optical substrate 100 of the thin film may include at least one first stacked structure 110. The optical thickness of each film layer in each group of the first stacked structure 110 may be different, that is, the optical thickness of the first film layer 111 and the second film layer 112 may be different. The optical thickness of the film layer is characterized as the product of the refractive index and the physical thickness of the film layer.

[0041] In other embodiments, such as Figure 3 As shown, the optical substrate 100 of the thin film may include at least two second stacked structures 120. An insertion layer 130 may be disposed between the second stacked structures 120. The optical thickness of each film layer in each group of films of each second stacked structure 120 may be the same, that is, the optical thickness of the third film layer 121 and the fourth film layer 122 may be the same. The optical thickness of the insertion layer 130 may be the average of the optical thicknesses of the corresponding films of adjacent second stacked structures 120, for example, the average of the optical thicknesses of the third film layer 121 or the fourth film layer 122 in two adjacent second stacked structures 120. The insertion layer 130 may include at least one of Ta2O5, TiO2, ZnS, and HfO2.

[0042] In some embodiments, the thin film may have multiple discrete target wavelengths. The target wavelength can be the reflection wavelength at which the reflectivity of the thin film exceeds a predetermined threshold. The predetermined threshold can be set to 99.9%.

[0043] In some embodiments, the number of film layers in the first stacked structure and / or the second stacked structure can be determined based on the reflectivity of the first stacked structure and / or the second stacked structure and the refractive index of each film layer in each group. The greater the difference in refractive index between the film layers, the higher the reflectivity of each film layer group, and the fewer groups are required. A larger number of groups will increase the complexity of the fabrication and stress accumulation. The number of groups can generally be set to 8 to 50.

[0044] According to embodiments of the present invention, a multi-wavelength thin film is provided. This thin film achieves multiple discrete target wavelengths by forming at least one first stacked structure or at least two second stacked structures on an optical substrate. The first and second stacked structures do not rely on conventional quarter-wavelength periodic stacking, and an intercalation layer is provided between the second stacked structures. This not only satisfies the requirement for multiple target wavelengths but also avoids the additional interface losses, thermal deformation misalignment, and structural complexity problems caused by gluing or splicing single-wavelength stacked structures.

[0045] like Figure 1 and Figure 2 As shown, the optical thicknesses of the first film layer 111 and the second film layer 112 in the first stacked structure 110 are different, and the sum of the optical thicknesses of the first film layer 111 and the second film layer 112 is a first preset thickness. The multiple discrete target wavelengths of this film can be in a multiple relationship. The first preset thickness can characterize half of the target wavelength corresponding to the first stacked structure 110.

[0046] Continue to refer to Figure 1 A first stacked structure 110 can be disposed on the optical substrate 100 of the thin film, such that the thin film can have a first target wavelength λ1 and a second target wavelength λ2 that are multiples of each other, and the first target wavelength λ1 is twice the second target wavelength λ2, i.e., λ2 = λ1 / 2. The target wavelength corresponding to the first preset thickness is the first target wavelength λ1, i.e., the first preset thickness is half of the first target wavelength λ1.

[0047] For example, if the first target wavelength λ1 and the second target wavelength λ2 of the thin film are 1560nm and 780nm respectively, then the sum of the optical thicknesses of the first film layer and the second film layer in the first stacked structure is 780nm.

[0048] Continue to refer to Figure 2Two first stacked structures 110 can be disposed on the optical substrate 100 of the thin film, such that the thin film can have a first target wavelength λ1 and a second target wavelength λ2 that are multiples of each other, and the first target wavelength λ1 is twice the second target wavelength λ2, i.e., λ2 = λ1 / 2. The target wavelengths corresponding to the first preset thicknesses of the two first stacked structures 110 are the first target wavelength λ1 and the second target wavelength λ2, respectively, i.e., the first preset thicknesses are half of the first target wavelength λ1 and half of the second target wavelength λ2, respectively.

[0049] For example, if the first target wavelength λ1 and the second target wavelength λ2 of the thin film are 1560nm and 780nm respectively, then the sum of the optical thicknesses of the first and second films in the first first stacked structure is 780nm, and the sum of the optical thicknesses of the first and second films in the second first stacked structure is 390nm.

[0050] In some embodiments, when the first target wavelength λ1 is twice the second target wavelength λ2, the sum of the optical thicknesses of the first film layer and the second film layer in the first stacked structure is half of the target wavelength, and the optical thicknesses of the two are different. The optical thickness of each film layer can be k times the first preset thickness, where the value of k can include 0.25~0.75, such as 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, etc.

[0051] Figure 4 The reflection spectrum of a multi-wavelength thin film according to an embodiment of the present invention is illustrated schematically.

[0052] like Figure 4 As shown, the thin film comprises two first stacked structures, with a first target wavelength λ1 and a second target wavelength λ2 of 1560 nm and 780 nm, respectively. The first stacked structure has an optical thickness of 0.15λ1 for the first film layer and 0.35λ1 for the second film layer, with 15 layers in total. The second stacked structure has an optical thickness of 0.15λ2 for the first film layer and 0.35λ2 for the second film layer, with 6 layers in total. It can be observed that the thin film exhibits a reflectivity exceeding 99.9% at both the first target wavelength λ1 and the second target wavelength λ2.

[0053] According to an embodiment of the present invention, by breaking the structural symmetry of a quarter wavelength, the higher refractive index film layer and the lower refractive index film layer are regarded as a whole functional unit, and the overall optical thickness is controlled. The interference behavior of the thin film will no longer be limited to the superposition of interface reflections of a single wavelength, but will be transformed into an overall interference effect, thereby forming reflections of multiple target wavelengths and providing the reflection requirements at multiple harmonic wavelengths.

[0054] Continue to refer to Figure 3In the second stacked structure 120, the third film layer 121 and the fourth film layer 122 have the same optical thickness and are both of the second preset thickness. The multiple discrete target wavelengths of this film can be in a non-multiple relationship. The second preset thickness can represent one-quarter of the target wavelength corresponding to each second stacked structure 120.

[0055] In some embodiments, two second stacked structures 120 may be provided on the optical substrate 100 of the thin film, such that the thin film may have a discrete third target wavelength λ3 and a fourth target wavelength λ4 that are not multiples of each other.

[0056] The target wavelengths corresponding to the second preset thickness in the two second stacked structures can be the third target wavelength λ3 and the fourth target wavelength λ4, respectively. That is, the second preset thickness can be one-quarter of the third target wavelength λ3 and one-quarter of the fourth target wavelength λ4, respectively. For example, if the third target wavelength λ3 and the fourth target wavelength λ4 of the thin film are 1397 nm and 1580 nm, respectively, then the optical thickness of the third and fourth films in the first second stacked structure can be 349 nm, the optical thickness of the third and fourth films in the second second stacked structure can be 395 nm, and the optical thickness of the insertion layer can be 372 nm.

[0057] Alternatively, the target wavelengths corresponding to the second preset thicknesses in both second stacked structures can be the average of the third target wavelength λ3 and the fourth target wavelength λ4, i.e., the second preset thickness can be one-quarter of the average of the third target wavelength λ3 and the fourth target wavelength λ4. For example, if the third target wavelength λ3 and the fourth target wavelength λ4 of the thin film are 1397 nm and 1580 nm, respectively, then the optical thicknesses of the third and fourth films in both second stacked structures, as well as the intercalation layer between the two second stacked structures, are all 372 nm.

[0058] In some embodiments, when the second preset thickness is the average of the third target wavelength λ3 and the fourth target wavelength λ4, the number of film layers in the two second stacked structures can be the same.

[0059] Figure 5 The reflection spectrum of a multi-wavelength thin film according to another embodiment of the present invention is illustrated schematically.

[0060] like Figure 5As shown, the thin film comprises two second stacked structures and an insertion layer. The third target wavelength λ3 and the fourth target wavelength λ4 are 1395 nm and 1580 nm, respectively. The thickness of the third layer, the fourth layer, and the insertion layer in the two second stacked structures is 372 nm, and there are 11 groups in each group. It can be found that the reflectivity of the thin film at the third target wavelength λ3 and the fourth target wavelength λ4 are 99.9963% and 99.9978%, respectively. Verification of the above thin film shows that when the thickness of each layer deviates by ±10 nm, its reflectivity is within an acceptable range, demonstrating excellent robustness and process feasibility.

[0061] According to an embodiment of the present invention, by introducing an insert layer between the second stacked structures, a Fabry-Perot cavity that transmits to the target wavelength can be formed with the optical substrate, separating the high reflectivity peak from the middle to form a double peak, breaking the bandwidth limitation of the single peak, thereby forming a higher reflectivity for multiple target wavelengths.

[0062] According to embodiments of the present invention, the aforementioned non-periodic structure breaks the symmetry constraints of traditional periodic films, effectively smoothing the group delay oscillations at the edges of the reflection band. This provides crucial support for low-dispersion applications such as ultrafast lasers, avoiding insertion loss, thermal management, and volume issues associated with gluing or splicing. Furthermore, the quasi-periodic design of the built-in Fabry-Perot cavity broadens the reflection bandwidth and enhances the robustness of the design while ensuring multi-band performance.

[0063] Figure 6 A flowchart illustrating a method for preparing a multi-wavelength thin film according to an embodiment of the present invention is shown.

[0064] like Figure 6 As shown, the preparation method of this embodiment may include operations S610 to S620.

[0065] In operation S610, the film parameters of at least one first stacked structure or at least two second stacked structures are determined.

[0066] In some embodiments, film parameters may include the optical thickness of each film layer and the number of groups. At least one first stacked structure may include multiple groups of film layers with different refractive indices stacked alternately, and the optical thickness of each film layer in each group may be different. An intercalation layer may be disposed between at least two second stacked structures. Each of the at least two second stacked structures may include multiple groups of film layers with different refractive indices stacked alternately, and the optical thickness of each film layer in each group may be the same. The optical thickness of the intercalation layer may be the average of the optical thicknesses of the corresponding film layers of each adjacent second stacked structure.

[0067] Figure 7 and Figure 8The optimal film parameter distribution and transmission spectrum of the multi-wavelength thin films according to embodiments of the present invention are schematically illustrated. It should be noted that... Figure 7 The red film shown is a tantalum oxide layer, and the blue film is a silicon oxide layer.

[0068] In this embodiment, film parameters are set within a preset range to meet the reflection requirements of multiple discrete target wavelengths. The preset range can include 20nm~400nm, such as 20nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, etc. Multiple target wavelengths and corresponding performance indicators are defined, such as reflectivity greater than 99.9% or transmittance less than 0.1%. A hybrid genetic algorithm is used to search for the optimal film parameters globally. After the genetic algorithm converges, local optimization algorithms such as sequential quadratic programming are used for optimization. Integrating parallel computing and result caching mechanisms can improve optimization efficiency and obtain the desired result. Figure 7 The optimal film parameter distribution results are shown. Further verification of the performance indicators of the optimized film parameters is needed to ensure they meet the set performance targets, such as... Figure 8 As shown, the target wavelength of this thin film can be 1064nm and 1550nm.

[0069] Current film thickness control methods based on setting deposition time require calibration of the deposition rate. Calibration methods based on reflectance spectra or scanning electron microscope sections have errors of 3nm to 5nm, which are difficult to meet the deposition requirements of multi-wavelength thin films. The following will present a film thickness calibration method based on reflectance spectra combined with scanning electron microscopy.

[0070] First, a stacked structure with five or more pairs of alternately stacked films of different refractive indices is prepared, with each layer of the same refractive index material having the same deposition time. Each pair of stacked structures includes a sample capable of measuring the reflection spectrum and a sample whose cross-section can be observed using a scanning electron microscope. Subsequently, an optical model is established, and the simulated reflection spectrum is obtained by scanning the optical thickness deviation parameters of the films with different refractive indices.

[0071] Figure 9 and Figure 10 The actual reflection spectrum and cross-sectional view of the multi-wavelength thin film according to an embodiment of the present invention are schematically shown.

[0072] like Figure 9 As shown, the height and position of the characteristic reflection peaks are extracted by testing the actual reflection spectrum of the sample. With the objective of minimizing the reflectance similarity function between the simulated and actual reflection spectra near the characteristic peaks, two sets of symmetric candidate solutions are obtained, corresponding to the cases of thicker higher refractive index films and thicker lower refractive index films, respectively. Figure 10As shown, a clear cross-sectional image of the film was taken using a scanning electron microscope, and the actual physical thickness of each film layer was measured. The actual physical thickness was then compared with two sets of symmetrical candidate solutions one by one, and the film layer parameters with the highest matching degree were the calibrated film layer parameters.

[0073] In operation S620, at least one first stacked structure or at least two second stacked structures are formed on the optical substrate based on the film parameters.

[0074] In some embodiments, the actual coating rate of each film layer can be obtained based on the actual physical thickness and the actual coating time, and the subsequent coating parameters can be corrected using the calibrated film layer parameters to achieve precise control of the film layer parameters.

[0075] In some embodiments, the thin film has multiple discrete target wavelengths. The target wavelength is the reflection wavelength when the reflectivity of the thin film is greater than a predetermined threshold.

[0076] According to embodiments of the present invention, the hybrid optimization algorithm, combined with parallel computing, can complete the design of complex films within hundreds of seconds. This not only significantly shortens the design cycle but also proactively predicts process risks, improving process feasibility. The aforementioned inversion method improves the accuracy of film parameters to the nanometer level, enhances the stability of the coating rate, and improves product yield.

[0077] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0078] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A multi-wavelength thin film, characterized in that, include: Optical substrate; as well as At least one first stacked structure on the optical substrate, wherein the at least one first stacked structure comprises multiple sets of alternately stacked film layers with different refractive indices; the optical thickness of each film layer in each set is different; or At least two second stacked structures on the optical substrate; wherein an insertion layer is disposed between the at least two second stacked structures, each of the at least two second stacked structures includes multiple sets of film layers with different refractive indices stacked alternately, the optical thickness between each film layer in each set of film layers of each second stacked structure is the same, and the optical thickness of the insertion layer is the average of the optical thicknesses of each film layer corresponding to each adjacent second stacked structure. The thin film has multiple discrete target wavelengths, and the target wavelength is the reflection wavelength when the reflectivity of the thin film is greater than a predetermined threshold.

2. The thin film according to claim 1, characterized in that, The sum of the optical thicknesses of each film layer in each group of films in at least one first stacked structure is a first preset thickness. The plurality of discrete target wavelengths are in a multiple relationship. The first preset thickness represents half of the target wavelength corresponding to each first stacked structure.

3. The thin film according to claim 2, characterized in that, When the thin film has a first target wavelength and a second target wavelength that are multiples of each other, and the first target wavelength is twice the second target wavelength, the target wavelength corresponding to the first preset thickness is the first target wavelength, or the target wavelength corresponding to the first preset thickness is the first target wavelength and the second target wavelength respectively.

4. The thin film according to claim 2, characterized in that, The optical thickness of each film layer in each group of films in the at least one first stacked structure is k times the first preset thickness, wherein the value of k includes 0.25 to 0.

75.

5. The thin film according to claim 1, characterized in that, The optical thickness of each film layer in each group of films in the at least two second stacked structures is a second preset thickness, and the plurality of discrete target wavelengths of the thin film are in a non-multiple relationship. The second preset thickness represents one-quarter of the target wavelength corresponding to each second stacked structure.

6. The thin film according to claim 5, characterized in that, When the thin film has a third target wavelength and a fourth target wavelength that are not multiples of each other, the target wavelengths corresponding to the second preset thickness are the third target wavelength and the fourth target wavelength, respectively, or the target wavelengths corresponding to the second preset thickness are the average of the third target wavelength and the fourth target wavelength.

7. The thin film according to claim 6, characterized in that, When the second preset thickness is the average of the third target wavelength and the fourth target wavelength, the number of each film layer in the at least two second stacked structures is the same.

8. The film according to any one of claims 1 to 7, characterized in that, The number of film layers in the at least one first stacked structure and / or the at least two second stacked structures is determined based on the reflectivity of the at least one first stacked structure and / or the at least two second stacked structures and the refractive index of each film layer in each group.

9. The thin film according to any one of claims 1 to 7, characterized in that, In the at least one stacked structure, each group of film layers includes a first film layer and a second film layer, and in the at least two stacked structures, each group of film layers includes a third film layer and a fourth film layer; The first film layer, the third film layer, and the insertion layer include at least one of Ta2O5, TiO2, ZnS, and HfO2; The second and fourth films include at least one of SiO2, Al2O3, and YbF3.

10. A method for preparing a multi-wavelength thin film, characterized in that, include: Determine the film layer parameters of at least one first stacked structure or at least two second stacked structures; wherein, the at least one first stacked structure comprises multiple sets of film layers with different refractive indices stacked alternately, and the optical thickness between each film layer in each set is different; an insertion layer is disposed between the at least two second stacked structures, each of the at least two second stacked structures comprises multiple sets of film layers with different refractive indices stacked alternately, and the optical thickness between each film layer in each set is the same, and the optical thickness of the insertion layer is the average of the optical thicknesses of the corresponding film layers of each adjacent second stacked structure; the film layer parameters include the optical thickness of each film layer and the number of sets; Based on the film parameters, at least one first stacked structure or at least two second stacked structures are formed on an optical substrate; wherein the thin film has multiple discrete target wavelengths, the target wavelengths being the reflection wavelengths when the reflectivity of the thin film is greater than a predetermined threshold.

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