A broad spectrum coded array filter and method of making the same

Abstract

The application discloses a preparation method of a wide-spectrum coding array filter, comprising the following steps: obtaining, by using a nano-imprinting method, an imprinted array structure with different heights in a first dimension at one time; and obtaining, by using an ultraviolet lithography-pattern transfer method, a lithography array structure with different heights in a second dimension on the obtained imprinted array structure, so as to finally obtain a wide-spectrum coding array filter with different heights. The application also discloses the wide-spectrum coding array filter prepared by the above method. The preparation method combines a nano-imprinting method, an ultraviolet lithography method, a thin film deposition method and other processing methods, the number of times of ultraviolet lithography-pattern transfer required by the preparation method can be greatly reduced, and the number of times of ultraviolet lithography-pattern transfer does not increase with the increase of the number of filter blocks. The similar preparation method can be applied to miniature (imaging) spectral chip / modules, miniature (imaging) spectrometers and other products, and is expected to be widely applied in the fields of portable industrial detection, portable agricultural detection and consumer electronics.

Description

Technical Field

[0001] This invention relates to the fields of micro-nano optoelectronic device fabrication, spectral sensing, and spectral imaging, and specifically to a broadband coded array filter and its fabrication method. Background Technology

[0002] Spectrometers are used to test the emission / reflection / transmission / radiation characteristics of calibrated light sources or objects, and are widely used in scientific research and industrial production. Today, the application areas of spectral analysis are rapidly expanding, further increasing the demand for smaller physical sizes and lower costs for spectrometers. In recent years, thanks to advancements in micro-nano fabrication technology and artificial intelligence algorithms, computational reconstruction-based miniature spectrometers have emerged. This approach utilizes algorithms such as compressed sensing and deep neural networks to invert the incident spectrum from a set of spectral responses encoded by a broadband detector or broadband filter. Theoretically, any optical element whose structure can be adjusted to produce different broadband spectral responses can be used as an encoding element, such as quantum dots, nanowires, thin films, liquid crystals, photonic crystals, and metasurfaces. Array filters based on thin film structures have become a highly competitive technological route in the industrialization of miniature spectrometers due to their low cost, mass production capability, and stable manufacturing process.

[0003] Nanoimprint lithography is increasingly being used in the fabrication of optical devices, and its high efficiency and speed are expected to be widely applied in fields such as spectral sensing, spectral imaging, and augmented reality displays. Unlike traditional ultraviolet lithography, nanoimprint lithography can create arbitrary patterns of different heights and periods on the same large-size substrate in a single operation. Based on this unique property, the different thicknesses of dielectric layers required for each block of a broadband array filter can be rapidly obtained using nanoimprint lithography, thereby significantly simplifying the arraying process of broadband filters and reducing the cost of the arraying process.

[0004] Based on the fundamental principles of compressed sensing, the broadband spectral response non-correlation of the filter block is positively correlated with its encoding efficiency and spectral reconstruction accuracy. However, the thickness variation range of the dielectric layer obtained by a single nanoimprint is relatively small, making it difficult to obtain a spectral response with high non-correlation. Furthermore, nanoimprint technology offers low precision in controlling the thickness of the obtained dielectric layer.

[0005] Reference (CN 114910166 A) uses electron beam evaporation to process each filter block separately, and then uses splicing, micro-nano fabrication and other methods to combine them to obtain a multi-peak valley broadband filter array. When using this method, multiple electron beam evaporation processes are required, and the number of processes is consistent with the number of filter blocks, resulting in low efficiency. Moreover, the size of a single filter block is on the order of millimeters, making it difficult to further miniaturize the spectrometer.

[0006] Reference (CN109932058A) employs multiple binary lithography separation processes to fabricate Fabry-Perot cavity filter arrays with metal / dielectric / metal structures. By adjusting the cavity path, it obtains single-narrow-peak transmission at different center wavelengths, but it cannot construct broadband multi-peak-valley spectra, thus affecting the effective encoding of the spectrum. In addition, the number of binary lithography separations required by this method is positively correlated with the number of filter blocks, resulting in relatively low processing efficiency. Summary of the Invention

[0007] This invention provides a broadband coded array filter and its fabrication method. This method utilizes micro / nano fabrication techniques such as nanoimprint lithography and ultraviolet lithography, along with thin film deposition techniques, to fabricate broadband coded array filters with a significantly increased range of dielectric layer thickness variations. The fabricated array filter has a single block size on the micrometer scale, which can greatly reduce the physical size of spectral chips, spectral modules, and spectrometers, enabling mass production of related products.

[0008] The array filter prepared by this invention overcomes the shortcomings of array filters obtained solely by nanoimprint technology, such as the small range of variation in the thickness of the spacer layer and the low non-correlation of the spectral response of each block. It enhances the encoding capability of the spectrum to be measured, thereby improving the accuracy of spectral reconstruction.

[0009] The array filter prepared by this invention overcomes the shortcomings of relying solely on ultraviolet lithography to prepare array filters, where the number of ultraviolet lithography steps required is positively correlated with the number of filter blocks. This simplifies the array filter processing flow and reduces the preparation cost.

[0010] This invention combines nanoimprinting with ultraviolet lithography-pattern transfer to prepare dielectric layer arrays with a wide range of thickness variations, thereby obtaining a highly uncorrelated spectral response and achieving efficient encoding of the spectrum to be measured.

[0011] This invention provides the following technical solution:

[0012] A method for fabricating a broadband coded array filter includes: obtaining an imprinted array structure with different heights in a first dimension in one step using a nanoimprinting method; obtaining a photolithographic array structure with different heights in a second dimension on the obtained imprinted array structure using an ultraviolet lithography-pattern transfer method, and finally obtaining a broadband coded array filter composed of multiple filter blocks with different heights; wherein the filter blocks are arranged in an array along two dimensions (the first dimension and the second dimension).

[0013] The coded array filter obtained by the above method consists of multiple filter blocks arranged in an array. Each filter block has a different structure and a different spectral response, but all of them are broadband responses covering the entire detection band.

[0014] Of course, the above structure can be further improved, for example, by adding a single layer or multiple layers of thin film on one or both sides of the structure. Preferably, a method for fabricating a broadband coded array filter includes: depositing a bottom single layer or multiple layers of thin film on a substrate using a thin film deposition method; obtaining an imprinted array structure with different heights in the first dimension on the surface of the bottom single layer or multiple layers of thin film using a nanoimprinting method; obtaining a photolithographic array structure with different heights in the second dimension on the obtained imprinted array structure using an ultraviolet lithography-pattern transfer method; and finally depositing a top single layer or multiple layers of thin film on the photolithographic array structure using a thin film deposition method to obtain the broadband coded array filter.

[0015] Preferably, the first and second dimensions are two dimensions that are perpendicular to each other. When converting to height data, the first and second dimensions can be converted into rows or columns.

[0016] Preferably, the height increases or decreases sequentially in the first or second dimension. More preferably, the height difference between two adjacent blocks in the first or second dimension is equal.

[0017] Before fabrication, this invention can determine the height difference between the first and second dimensions based on the height distribution of the filter blocks in the coded array filter; thereby determining the process parameters for the nanoimprinting and UV lithography-pattern transfer methods. The first and second dimensions are generally two mutually perpendicular dimensions. For example, during design, the array filter can adopt an array structure with filter blocks arranged in the x and y directions, with the height increasing layer by layer in the first dimension (e.g., the x-direction); the height also increases layer by layer in the second dimension (e.g., the y-direction), and all structures in the final array structure have different heights. The height difference in the first dimension is used to determine the template structure in the nanoimprinting process, and the height difference in the second dimension is used to determine the film deposition thickness in the UV lithography-pattern transfer process.

[0018] Furthermore, a method for fabricating a broadband coded array filter includes:

[0019] S3: Deposit a single or multiple thin film on a clean substrate using a thin film deposition method;

[0020] S4: Using nanoimprinting, an imprinted array structure with different heights is obtained in one step on the structure described in S3;

[0021] S5: Obtain patterned photoresist on the structure described in S4 using ultraviolet lithography;

[0022] S6: Deposit a thin film on the structure described in S5 using physical vapor deposition (PVD) technology;

[0023] S7: Use organic solvents (acetone, resist remover, etc.) to strip the photoresist and the thin film above the photoresist from the array structure;

[0024] S8: Repeat S5-S7 on the structure obtained in S7. The number of repetitions does not need to be positively correlated with the number of array filter blocks.

[0025] S9: Deposit a top single-layer or multi-layer thin film on the structure described in S8 using thin film deposition technology.

[0026] Furthermore, prior to step S3:

[0027] S1: Determine the number of filter blocks required for the array filter; select the substrate material and film material of the filter blocks according to the working wavelength range;

[0028] S2: Wipe and clean the substrate using ethanol, acetone, etc.

[0029] In this invention, the detection band is the ultraviolet-visible-infrared band, and the specific band is selected as needed.

[0030] The "several" refers to two or more.

[0031] The substrate material is a transparent substrate material, and the ultraviolet-visible-near infrared band is selected from glass or plastic. Preferably, the substrate is K9 glass or PET plastic; the mid-far infrared band is selected from silicon, germanium, zinc sulfide, zinc selenide and fluorides such as calcium fluoride.

[0032] The printing adhesive can be a hot printing adhesive, such as polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC), etc., or a UV printing adhesive, a step printing adhesive, a rolling printing adhesive, etc.

[0033] The multilayer thin film is made of transparent or low-absorption materials within the operating wavelength range. Preferably, it is a multilayer all-dielectric film or a metal-dielectric structure film stack with high / low refractive index.

[0034] In the multilayer all-dielectric film, the high-refractive-index layer material is selected from one or a combination of at least two of titanium dioxide, hafnium dioxide, tantalum pentoxide, silicon nitride, or zinc sulfide in the ultraviolet-visible-near-infrared band; the far-infrared band of the high-refractive-index layer material is selected from one or a combination of at least two of silicon, germanium, zinc sulfide, or zinc selenide. In the low-refractive-index layer material, the ultraviolet-visible-near-infrared band is selected from one or a combination of at least two of silicon dioxide, aluminum oxide, or metal fluorides; the far-infrared band of the low-refractive-index layer material is selected from one or a combination of at least two of zinc sulfide, zinc selenide, or metal fluorides. The metal fluoride may be magnesium fluoride.

[0035] Preferably, the number of layers in the multilayer dielectric film is 1-50. More preferably, it has 3-20 layers, and even more preferably, it has 3-10 layers.

[0036] Preferably, the thickness of a single layer of the multilayer all-dielectric film is 5-3000 nm, and the thickness of each layer can be the same or different.

[0037] Preferably, the metal-dielectric structured film stack is a metal / dielectric / metal broadband filter film system from bottom to top.

[0038] The metal layer material in the metal / dielectric / metal broadband filter film system is selected from one or an alloy of at least two of gold, silver, aluminum, or copper; the dielectric layer material in the ultraviolet-visible-near-infrared band is selected from one or a combination of at least two of silicon dioxide, aluminum oxide, metal fluorides, titanium dioxide, hafnium dioxide, tantalum pentoxide, silicon nitride, or zinc sulfide; and the dielectric layer material in the infrared band is selected from one or a combination of at least two of silicon, germanium, zinc sulfide, zinc selenide, or metal fluorides. The metal fluoride may be magnesium fluoride.

[0039] Preferably, in the metal / dielectric / metal broadband filter film system, the metal layer thickness is 6nm-70nm and the dielectric layer thickness is 15nm-10μm. The metal layer thicknesses can be the same or different.

[0040] The specific structures of the aforementioned membranes can all be obtained by optimizing existing simulation or computer algorithms.

[0041] Each filter block in the broadband coded array filter is composed of several (one or more groups) high and low refractive index films stacked alternately. One of the films (such as a low refractive index layer) is fabricated using the nanoimprinting method to obtain the imprinted array structure, and the adjacent film layer above it is obtained using the ultraviolet lithography-pattern transfer method to obtain the lithographic array structure.

[0042] Preferably, before fabrication, the filter blocks of the target array filter are arranged in a height distribution array, and the height increases or decreases sequentially in the row or column direction. Based on the height distribution in the two directions, the template structure in the nanoimprint method and the coating thickness in the ultraviolet lithography-pattern transfer method are determined.

[0043] Preferably, the height difference between two adjacent blocks in the first dimension (or row) is 10–40 nm, and the height difference between two adjacent blocks in the second dimension (or column) is 100–500 nm.

[0044] The filter film array is prepared using a variety of processing methods, including nanoimprinting, ultraviolet lithography-pattern transfer, and thin film deposition.

[0045] The nanoimprinting includes methods such as thermal imprinting, ultraviolet imprinting, and microcontact printing. Preferably, thermal imprinting is used.

[0046] The thin film deposition includes physical vapor deposition methods such as electron beam evaporation, ion beam sputtering, and magnetron sputtering; chemical vapor deposition methods such as surface plasmon chemical vapor deposition and low-pressure chemical vapor deposition may also be used; and methods such as ion plating, electroplating, and arc plating may also be employed. Preferably, electron beam evaporation is used.

[0047] In the filter array, film layers of varying thicknesses in different blocks are fabricated using a combination of nanoimprinting and ultraviolet lithography-pattern transfer methods. Preferably, the nanoimprinting and ultraviolet lithography-deposition pattern transfer method is used, which includes steps such as ultraviolet lithography, thin film deposition, and solution stripping.

[0048] A broadband coded array filter includes a substrate and a filter film system on the substrate. The broadband coded array filter contains several blocks with different structures, and different spectral responses (often containing different numbers of peaks and valleys) are achieved in each block through a combination of nanoimprinting, ultraviolet lithography-pattern transfer, and thin film deposition. However, all spectral responses are broadband responses covering the entire detection band.

[0049] The present invention also provides a broadband coded array filter, which is prepared by the preparation method described in any of the above technical solutions.

[0050] This invention combines nanoimprinting with ultraviolet lithography-pattern transfer to prepare dielectric layers with a wide thickness range, thereby obtaining highly uncorrelated spectral responses and achieving efficient encoding of the measured spectra. Furthermore, the combination of nanoimprinting and thin film deposition compensates for the lower precision of nanoimprinting in controlling dielectric layer thickness, thus improving the accuracy of the obtained dielectric layer thickness gradient.

[0051] The broadband coded array filter and its fabrication method of the present invention have the following advantages compared with other array filters and their fabrication methods used for micro-spectral sensing:

[0052] (1) By using micro-nano processing methods such as nanoimprinting and ultraviolet lithography-pattern transfer, the physical size of the spectrometer can be further reduced to the micrometer and submicrometer scale.

[0053] (2) By employing micro-nano fabrication methods such as nanoimprinting and ultraviolet lithography-pattern transfer, compared with array filters prepared by single nanoimprinting, the thickness of the spacer layer is increased, thereby improving the complexity of the array filter structure and the spectral response of each block and increasing the spectral coding efficiency. In addition, combining nanoimprinting with thin film deposition can compensate for the low precision of nanoimprinting in controlling the thickness of the spacer layer, thus improving the accuracy of the obtained spacer layer thickness gradient.

[0054] (3) Using micro-nano processing methods such as nanoimprinting and ultraviolet lithography-pattern transfer, compared with the method of multiple binary lithography separation (Chinese patent document with publication number CN109932058A), the number of ultraviolet lithography-pattern transfers does not need to be changed due to the increase in the number of array filter blocks, simplifying the processing flow of array filters and reducing processing costs;

[0055] (4) Using broadband filters as filter blocks increases the encoding capability of filter blocks compared to using narrowband filters, making the number of filter blocks much smaller than the number of spectral channels, thus simplifying the array filter processing flow.

[0056] (5) The filter block with thin film structure reduces the processing difficulty and cost and improves the process stability compared with structures based on quantum dots, nanowires, metasurfaces, etc.

[0057] (6) The filter block with thin film structure has good angle insensitivity, which reduces the impact of errors in actual use on the spectral reconstruction results.

[0058] This invention is a novel, miniaturized, and integrable broadband coded array filter. Similar fabrication methods can be applied to products such as miniature (imaging) spectral chips, miniature (imaging) spectral modules, and miniature (imaging) spectrometers. It is expected to be widely used in portable industrial testing, portable agricultural testing, consumer electronics, and other fields. Attached Figure Description

[0059] Figure 1 This is a schematic diagram illustrating the mass production of the broadband coded array filter provided by the present invention;

[0060] Figure 2 A schematic diagram of the key step I, nanoimprinting, in the optimal fabrication method for broadband coded array filters;

[0061] Figure 3 A schematic diagram of the key step II of the optimal fabrication method for broadband coded array filters: ultraviolet lithography-deposition method for pattern transfer.

[0062] Figure 4 A schematic diagram of nanoimprinting, ultraviolet lithography template, and the resulting filter block in the preferred fabrication method for a broadband coded array filter;

[0063] Figure 5 A schematic diagram of the structure of the broadband coded array filter obtained by the preferred preparation method;

[0064] Figure 6 This is a schematic diagram of a single block structure of a broadband coded array filter in the embodiment;

[0065] Figure 7The spectral response of a portion of the broadband coded array filter in this embodiment is shown. Detailed Implementation

[0066] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0067] like Figure 1 The diagram illustrates the mass production capability of the broadband coded array filter provided by this invention. Specifically, through a single fabrication process (including nanoimprinting, ultraviolet lithography, and thin film deposition), several array filters 102 can be fabricated on a substrate 101 in a single operation. Each array filter 102 consists of several filter blocks 103 with different structural parameters. For illustration, 64 filter blocks with different structural parameters form a 4×16 rectangular array filter, but the number of filter blocks is not limited to 64. The specific number of filter blocks, film structure, and materials can all be determined using existing methods, such as the applicant's previously filed patent document (CN114910166A) or other methods (CN109932058A). The focus of this invention is on how to achieve efficient and high-precision manufacturing of the aforementioned array filter.

[0068] A schematic diagram of the preferred fabrication method for broadband coded array filters, including thin film deposition and key steps (I) nanoimprinting, is shown below. Figure 2 As shown, (a) is the cleaning of the substrate, including but not limited to wiping and cleaning the substrate with solutions such as ethanol and acetone; (b) is the deposition of a single or multiple thin film on the clean substrate according to parameter requirements. The techniques that can be used include, but are not limited to, physical vapor deposition methods such as electron beam evaporation, ion beam sputtering, and magnetron sputtering; chemical vapor deposition methods such as surface plasmon chemical vapor deposition and low-pressure chemical vapor deposition; and methods such as ion plating, electroplating, and arc plating; (c)-(e) are the nanoimprinting process: (c) is the spin coating of the imprinting adhesive, controlling the thickness of the imprinting adhesive by controlling parameters such as spin coating time, rotation speed, and acceleration; (d) is imprinting and curing, including pressing a patterned template onto the imprinting adhesive with a certain pressure and curing the imprinting adhesive by ultraviolet light irradiation or heating; (e) is demolding. Using step I, a film structure with gradually increasing height in the x-direction (the first dimension, which can be defined as the row direction) is obtained. At a certain height, the blocks contained in the corresponding column have equal heights. If Figure 2 As shown in (e), this is a side view of the current membrane structure; the corresponding top view can be found in [reference]. Figure 4 (b)

[0069] Key steps in the preferred fabrication method of broadband coded array filters: II. Schematic diagram of pattern transfer using ultraviolet lithography-deposition method (as shown in the image). Figure 3As shown, (a)-(d) represent the pattern transfer process of a single deposition method: (a) shows the process in... Figure 2 (a) Photoresist is spin-coated onto the obtained structure. The thickness of the photoresist is controlled by adjusting parameters such as spin-coating time, rotation speed, and acceleration. (b) Photoresist patterning includes pre-baking, alignment, exposure, development, and post-baking. (c) Thin film deposition can be performed using techniques including, but not limited to, physical vapor deposition methods such as electron beam evaporation, ion beam sputtering, and magnetron sputtering; chemical vapor deposition methods such as surface plasmon chemical vapor deposition and low-pressure chemical vapor deposition; and methods such as ion plating, electroplating, and arc plating. (d) Stripping of the patterned photoresist obtained in (b) and the thin film obtained in (c) above it, including but not limited to using organic solutions such as acetone and resist remover. Processes (e)-(h) and (i)-(l) are the same as (a)-(d), including photoresist spin-coating, photoresist patterning, thin film deposition, and photoresist stripping. However, different photolithography templates are used to adjust the thickness of the second-direction film layer in different filter blocks according to a certain rule. As an illustration, a broadband coded filter containing 64 blocks (4×16) uses three UV lithography-pattern transfers, but the number of UV lithography-pattern transfers is not limited to three. If a binary lithography separation method (Chinese patent document publication number CN109932058A) is used to prepare an array filter containing 64 structurally different blocks, at least six binary lithography separations are required. The method of this invention can reduce workload, and in mass production, it can significantly improve manufacturing efficiency, increase yield, and reduce manufacturing costs.

[0070] The schematic diagram of the nanoimprinting, ultraviolet lithography template, and the resulting filter block in the preferred fabrication method of the broadband coded array filter is shown below. Figure 4As shown. (a) is the nanoimprint template, with 16 regions; (b) are the 16 blocks obtained from the nanoimprint; (a) and (b) are completed in step I; (c) is the UV lithography template A, with 2 regions and a light-to-dark area ratio of 1:3, where the bright areas are not obscured by the cured photoresist; (d) are the 32 blocks obtained after the first deposition pattern transfer, where blocks 1-16 correspond to the original rectangular blocks obtained from the nanoimprint, and blocks 17-32 are rectangular blocks with a deposited film layer; (e) is the UV lithography template B, with 2 regions and a light-to-dark area ratio of 1:1; (f) is the second... After the deposition pattern transfer, 48 blocks are obtained. Blocks 1-16 correspond to the original height obtained from the nanoimprint, blocks 17-32 are rectangular blocks with one layer of film deposited, and blocks 33-48 are rectangular blocks with two layers of film deposited. (g) is the UV lithography template C, consisting of two regions with a light-to-dark area ratio of 3:1. (h) is the 64 blocks obtained after the third deposition pattern transfer. Blocks 1-16 correspond to the original rectangular blocks obtained from the nanoimprint, blocks 17-32 are rectangular blocks with one layer of film deposited, blocks 33-48 are rectangular blocks with two layers of film deposited, and blocks 49-64 are rectangular blocks with three layers of film deposited. The final rectangular blocks 1-64 correspond to the 64 filter blocks of the array filter.

[0071] The specific process is as follows: On a substrate with a specified film system, a nanoimprint template is used for imprinting to obtain 16 blocks, namely 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16, as shown below. Figure 4 As shown in (b); on the imprinted structure, a first ultraviolet lithography was performed using ultraviolet lithography template A, and a thin film of a specified thickness was deposited. After peeling, 32 blocks were obtained, namely 1, 2, 3, ..., 30, 31 and 32, as shown. Figure 4 As shown in (d); on the structure obtained from the first UV lithography-pattern transfer, a second UV lithography is performed using UV lithography template B, and a film of a specified thickness is deposited. After peeling, 48 blocks are obtained, namely 1, 2, 3, ..., 46, 47 and 48, as shown in (d). Figure 4 As shown in (f); on the structure obtained from the second UV lithography-pattern transfer, a third UV lithography is performed using UV lithography template C, and a film of a specified thickness is deposited. After peeling, 64 blocks are obtained, namely 1, 2, 3, ..., 62, 63 and 64, as shown in (f). Figure 4 As shown in (h). For illustration, a nanoimprint template with 16 regions is used here, but the pattern of the imprint template used is not limited to this. For illustration, three photomasks with different light-transmitting areas are used here, but the pattern of the photomasks used is not limited to this, and the number of photomasks is not limited to this.

[0072] A schematic diagram of the broadband coded array filter structure obtained by the preferred preparation method is shown below. Figure 5 As shown. Among them, Figure 5 (a) is Figure 4 The rectangular blocks formed by the numbers 1, 2, 3, ..., 14, 15, and 16 obtained during preparation... Figure 5 (b) is Figure 4 The rectangular blocks formed by the prepared numbers 17, 18, 19, ..., 30, 31, and 32, Figure 5 (c) is Figure 4 The rectangular blocks formed by the obtained numbers 33, 34, 35, ..., 46, 47, and 48, Figure 5 (d) is Figure 4 The rectangular blocks formed by the obtained numbers 49, 50, 51, ..., 62, 63, and 64.

[0073] A schematic diagram of a single-block structure of a broadband coded array filter in the embodiment is shown below. Figure 6 As shown, 61 is the top layer film obtained by electron beam evaporation, 62 is the film obtained by ultraviolet lithography-pattern transfer, 63 is the imprinting adhesive obtained by thermal nanoimprinting, 64 is the bottom layer film obtained by electron beam evaporation, and 65 is the substrate. For illustration, the filter area here is prepared sequentially using electron beam evaporation, thermal nanoimprinting, ultraviolet lithography-pattern transfer, and electron beam evaporation, but the preparation process is not limited to this.

[0074] The spectral response of a portion of the broadband coded array filter in Example 1 is as follows: Figure 7 As shown, different filter blocks have different broadband spectral responses due to their different structures.

[0075] Example 1

[0076] The miniature spectrometer provided in this embodiment has a detection range of 400nm-700nm across the entire wavelength band.

[0077] The broadband coded array filter has 64 filter blocks. The substrate is JGS1 glass, and the film system is a broadband filter system of Sub(substrate) / TiO2 / SiO2 / PMMA / TiO2 / SiO2 / TiO2 / Air. The refractive index of the imprinting adhesive is 1.55. The structural parameters of each film layer are shown in Table 1.

[0078] Table 1 Structural parameters of the broadband coded array filter

[0079] Number of film layers Membrane materials Physical thickness / nm 1 TiO2 59.74 2 SiO2 94.50 3 PMMA 20-320 4 <![CDATA[TiO2]]> 320 / 640 / 960 5 <![CDATA[SiO2]]> 94.50 6 <![CDATA[TiO2]]> 59.74

[0080] That is, the physical thicknesses of the third layer (PMMA, fabricated using thermal nanoimprinting) and the fourth layer (high refractive index material TiO2, fabricated using ultraviolet lithography-deposition pattern transfer) in each filter block are different, while the film materials and physical thicknesses of the other layers are the same. The thicknesses of the third and fourth layers in each filter block are shown in Table 2.

[0081] Table 2 Physical thickness of the 3rd and 4th film layers in the filter block

[0082]

[0083]

[0084] The fabrication process of the broadband coded array filter is as follows:

[0085] (1) Wipe and clean the substrate with ethanol, acetone, etc.;

[0086] (2) Thin film deposition: 59.74 nm TiO2 and 94.50 nm SiO2 were deposited on a clean substrate using electron beam evaporation;

[0087] (3) Thermal nanoimprinting: using on the structure obtained in (2) Figure 4 (a) An imprint template was used to obtain 16 blocks with different film systems, each block having a thickness of 20nm, 40nm, 60nm, ..., 280nm, 300nm, and 320nm;

[0088] (4) First UV lithography-deposition pattern transfer: on the structure obtained in (3) Figure 4 (c) Ultraviolet lithography template A yields 32 blocks with different structures;

[0089] (5) Thin film deposition: TiO2 with a thickness of 320 nm was deposited on the structure obtained in (4) by electron beam evaporation;

[0090] (6) Use acetone to strip the photoresist and the TiO2 film above the photoresist from the structure obtained in (5);

[0091] (7) Second UV lithography-deposition pattern transfer: on the structure obtained in (6) Figure 4 (e) Ultraviolet lithography template B yields 48 blocks with different structures;

[0092] (8) Thin film deposition: TiO2 with a thickness of 320 nm was deposited on the structure obtained in (7) by electron beam evaporation;

[0093] (9) Use acetone to strip the photoresist and the TiO2 film above the photoresist from the structure obtained in (8);

[0094] (10) Third UV lithography-deposition pattern transfer: using the structure obtained in (9) Figure 4 (g) The ultraviolet lithography template C yields 64 blocks with different structures;

[0095] (11) Thin film deposition: TiO2 with a thickness of 320 nm was deposited on the structure obtained in (10) by electron beam evaporation;

[0096] (12) Use acetone to strip the photoresist and the TiO2 film above the photoresist on the structure obtained in (11);

[0097] (13) Thin film deposition: 94.50 nm SiO2 and 59.74 nm TiO2 films were deposited on the structure obtained in (12) using electron beam evaporation.

[0098] The number of layers in the aforementioned broadband coding array filter film system can be extended to more than 6 layers to increase the complexity of the spectral response and improve the coding capability.

[0099] The number of filter blocks in the aforementioned wideband coded array can be expanded to more than 64 to improve the accuracy of spectral reconstruction.

[0100] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a broadband coded array filter, characterized in that, include: Nanoimprinting methods were used to obtain imprinted array structures with different heights in the first dimension in a single step. On the obtained imprinted array structure, an ultraviolet lithography-pattern transfer method is used to obtain a lithographic array structure with different heights in the second dimension, and finally a broadband coded array filter composed of multiple filter blocks with different heights is obtained, wherein the filter blocks are arranged in an array along two dimensions. Specifically, a single or multiple thin film is deposited on a substrate using a thin film deposition method; an imprint array structure with different heights in the first dimension is obtained on the surface of the single or multiple thin film using a nanoimprint method; a photolithography array structure with different heights in the second dimension is obtained on the obtained imprint array structure using an ultraviolet lithography-pattern transfer method; and finally, a single or multiple thin film is deposited on the photolithography array structure using a thin film deposition method to obtain the broadband coded array filter. The height difference between two adjacent blocks in the first dimension is 10~40 nanometers, and the height difference between two adjacent blocks in the second dimension is 100~500 nanometers. The first dimension and the second dimension are two dimensions that are perpendicular to each other.

2. The method for preparing the broadband coded array filter according to claim 1, characterized in that, In the first or second dimension, the height increases or decreases sequentially, and the difference between adjacent heights is equal.

3. The method for preparing the broadband coded array filter according to claim 1, characterized in that, include: S3: Deposit a single or multiple thin film on a substrate using a thin film deposition method; S4: Nanoimprinting is used to obtain imprinted array structures with different heights on the structure obtained in S3 in one step; S5: A patterned photoresist is obtained on the structure obtained in S4 using ultraviolet lithography; S6: A thin film is deposited on the structure obtained in S5 using a thin film deposition method; S7: Use an organic solution to peel off the photoresist and the thin film above the photoresist from the array structure; S8: Repeat S5-S7 on the structure obtained in S7 to obtain the photolithographic array structure; S9: A single or multiple top-layer thin film is deposited on the structure obtained in S8 using a thin film deposition method to obtain a broadband coded array filter.

4. The method for preparing the broadband coded array filter according to claim 1, characterized in that, The broadband coded array filter comprises one or more sets of high and low refractive index films stacked alternately, wherein a certain film layer is fabricated using the nanoimprinting method to obtain the imprinted array structure, and the upper adjacent film layer is fabricated using the ultraviolet lithography-pattern transfer method to obtain the lithographic array structure.

5. A broadband coded array filter, prepared by the preparation method according to any one of claims 1 to 4.

Images