Multi-channel filtering chip synergistically regulated by fp cavity and metasurface and preparation method thereof

Abstract

This invention discloses a multi-channel filter chip and its fabrication method that are synergistically modulated by FP cavities and metasurfaces. The multi-channel filter chip, synergistically modulated by FP cavities and metasurfaces, comprises, from bottom to top, a transparent substrate, a lower reflective layer, a metasurface micro / nanostructure, a dielectric layer, and an upper reflective layer. The metasurface micro / nanostructure is an array of subwavelength nanostructures. Within a region corresponding to a filter channel, the structural parameters of the subwavelength nanostructures exhibit uniform and monotonically varying characteristics, and the transmission wavelength is evenly distributed within the corresponding sub-interval. The dielectric layer has N preset thicknesses in different regions, forming N FP cavity units with different cavity lengths, each corresponding to N filter channels. The upper reflective layer, together with the lower reflective layer and the dielectric layer, constitutes the FP cavity structure. The FP cavities and metasurface micro / nanostructures work synergistically to modulate the incident spectrum. This invention forms a high-density narrowband filter channel with several times the number of cavity lengths within a wide wavelength range of 900-1700 nm, while maintaining a limited number of cavity lengths.

Description

Technical Field

[0001] This invention belongs to the field of spectral analysis and micro / nano manufacturing technology, specifically relating to a multi-channel filter chip with synergistic control of FP cavity and metasurface and its fabrication method. Background Technology

[0002] With the increasing demand for miniaturized and portable spectral detection equipment in global industrial testing, scientific research analysis, and environmental monitoring, micro-spectrometers have become a research hotspot in academia and industry in recent years. Among the many technical approaches, the integration of micro- and nano-optical filtering elements with image sensor chips has attracted much attention, with filter chips based on Fabry-Perot microcavity arrays and metasurface arrays being the two main directions.

[0003] Fabry-Perot microcavities (FPCs) achieve highly selective filtering for specific wavelengths based on the principle of multi-beam interference. By integrating FPC arrays of different cavity lengths onto the surface of an image sensor and combining them with back-end reconstruction algorithms, the complete spectrum of the analyte can be recovered from the acquired multi-channel signals. This narrowband filtering scheme theoretically achieves high spectral resolution, but its performance is highly dependent on the scale of the FPC array—to cover a wide wavelength range, a sufficient number of FPC units with different cavity lengths need to be fabricated, which places stringent requirements on micro / nano fabrication processes. Currently, mainstream FPC fabrication technologies include electron beam grayscale direct writing, laser direct writing, grayscale lithography, and combinations of multiple lithography and etching processes. The first two methods are limited by the low efficiency of point-by-point scanning and the high equipment cost, making mass production difficult; the latter methods suffer from limitations in mask precision or error accumulation during multi-step overlay processes, making it difficult to control cavity length accuracy and uniformity. These technological bottlenecks directly restrict the number of channels in the FPC array, thus limiting the resolution and applicable wavelength range of the spectrometer.

[0004] Metasurfaces, as planar optical elements composed of subwavelength nanostructures, can achieve different spectral response characteristics by controlling the geometric dimensions of the nanostructures, and also have the potential for integration with image sensors. However, metasurface filtering schemes also face the dilemma of not being able to achieve both high resolution and wide spectral band: narrowband filtering metasurfaces can achieve high spectral resolution, but their applicable wavelength range is relatively narrow; broadband filtering metasurfaces can cover a wider spectral band, but due to the strong correlation of spectral responses between different units, coupled with the limitations of current processing precision, it is difficult to achieve high-precision spectral reconstruction.

[0005] The current micro-nano optical filter chip-based micro-spectrometer technology mainly faces the following core problems:

[0006] First, it is difficult to achieve both high performance targets simultaneously. Whether using a single FP-cavity array or a metasurface array, there is an inherent contradiction between high spectral resolution and wide detection band. Narrowband filtering schemes offer high resolution but have limited band coverage, while broadband filtering schemes offer wide band coverage but have limited resolution, making it difficult to simultaneously meet the requirements of wide-band and high-precision spectral detection.

[0007] Second, the complexity of the process and the insufficiency of mass production stability. FP cavity arrays have extremely high requirements for cavity length accuracy and uniformity, and existing processing technologies are unable to achieve low-cost mass production while ensuring accuracy. Although metasurface arrays can be realized through processes such as nanoimprinting, their spectral response is highly correlated and sensitive to processing errors, which also limits the final spectral reconstruction performance.

[0008] Third, the number of channels and reconstruction accuracy are limited. Due to the aforementioned technological bottlenecks, the number of available spectral channels in existing filter chips is limited, and the spectral response independence between channels is insufficient. This makes it difficult for the back-end reconstruction algorithm to recover high-fidelity complete spectral information from the limited-dimensional measurements, ultimately affecting the overall performance of the miniature spectrometer.

[0009] Therefore, how to overcome the performance limitations of a single FP cavity array or a single metasurface array, achieve high-resolution spectral detection over a wide band with a limited number of cavity lengths through structural synergy and functional complementarity between FP cavities and metasurfaces, and solve the resulting problems of process compatibility and mass production consistency are technical problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0010] The first objective of this invention is to provide a multi-channel filter chip that synergistically controls FP cavity and metasurface, addressing the problems in the prior art such as the difficulty in achieving both high spectral resolution and wide detection band, the difficulty in controlling the fabrication accuracy of FP cavity length, and the complexity and high cost of traditional micro-nano fabrication processes.

[0011] Therefore, the following technical solution is adopted to achieve the above objectives:

[0012] A multi-channel filter chip with FP cavity and metasurface synergistic control is constructed by stacking a transparent substrate, a lower reflective layer, a metasurface micro / nano structure, a dielectric layer, and an upper reflective layer sequentially from bottom to top.

[0013] The metasurface micro / nano structure is an array of subwavelength nanostructures. Within a region corresponding to a filter channel, the structural parameters of the subwavelength nanostructures exhibit uniform and monotonic variation, and the transmission wavelengths are evenly distributed within the corresponding sub-intervals, enabling fine-tuning of filtering in different bands.

[0014] The dielectric layer has N preset thicknesses in different regions, forming N FP cavity units with different cavity lengths, each corresponding to N filter channels; the upper reflective layer, together with the lower reflective layer and the dielectric layer, constitutes the FP cavity structure.

[0015] The FP cavity and the metasurface micro / nano structure work together to modulate the incident spectrum: the N preset thicknesses of the dielectric layer divide the target wavelength band into N sub-intervals, achieving preliminary screening across the entire wavelength band; by adjusting the structural parameters of the subwavelength nanostructures corresponding to each region, the transmission wavelength of each filter channel is continuously shifted within its respective sub-interval, thus forming narrowband filter channels covering a wide wavelength band with different preset values ​​corresponding to a limited number of cavity lengths; the transmission response of each filter channel satisfies the following relationship with the incident spectrum:

[0016]

[0017] Where i represents the channel number, λ represents the wavelength, λ2 is the longest wavelength of the working band, λ1 is the starting wavelength of the working band, and I i Let S(λ) be the light intensity signal acquired by the i-th channel, and E be the incident spectrum. i (λ) is the spectral response function of the photodetector, T i (λ) is the transmittance function of the i-th channel; the transmittance functions T of all channels are obtained through pre-calibration. i (λ), and combined with the acquired light intensity signal I i The incident spectrum S(λ) can then be solved using a spectral reconstruction algorithm.

[0018] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0019] As a preferred embodiment of the present invention: the lower reflective layer and the upper reflective layer are metal reflective layers or distributed Bragg reflectors;

[0020] The metal reflective layer is made of Au or Ag material;

[0021] The distributed Bragg reflector is composed of alternating stacks of high-refractive-index and low-refractive-index dielectric materials.

[0022] As a preferred technical solution of the present invention: the material of the metasurface micro / nano structure is a high refractive index medium material, including silicon nitride, amorphous silicon or silicon carbide; the metasurface micro / nano structure is a nanopillar array, a nanopore array or a nanofin array, and its structural parameters include period, diameter, width or height.

[0023] As a preferred technical solution of the present invention: the metasurface micro-nano structure is a periodic a-Si nanocylindrical array with a fixed period P=400nm and a height H=200nm. By uniformly varying the diameter D within the range of 100-300nm, the resonance peak of the metasurface micro-nano structure is continuously shifted within its respective FP cavity sub-band. When the diameter increases, the resonance peak shifts towards the longer wavelength direction.

[0024] As a preferred technical solution of the present invention: the material of the dielectric layer is photoresist, including SU-8 photoresist.

[0025] As a preferred technical solution of the present invention: the target wavelength is the 900-1700nm near-infrared band; the preset thickness range of the dielectric layer is 250-750nm; the metasurface micro-nano structure is a periodic amorphous silicon nanocylindrical array with a period of 400nm, a height of 200nm, and a diameter varying in the range of 100-300nm.

[0026] The second objective of this invention is to provide a method for fabricating a multi-channel filter chip that synergistically regulates FP cavity and metasurface, addressing the problems in the prior art such as the difficulty in achieving both high spectral resolution and wide detection band, the difficulty in controlling the fabrication accuracy of FP cavity length, and the complexity and high cost of traditional micro-nano fabrication processes.

[0027] Therefore, the following technical solution is adopted to achieve the above objectives:

[0028] The fabrication method of a multi-channel filter chip with synergistic modulation of FP cavity and metasurface includes the following steps:

[0029] S1. Initial mold fabrication process: The initial mold for the metasurface and the initial mold for the FP cavity are fabricated separately. The initial mold for the metasurface is formed on a hard substrate using a combination of high-precision photolithography and dry etching. The initial mold for the FP cavity is formed on a substrate using a three-dimensional micro-nano fabrication process, which forms a three-dimensional structure with multiple different step heights, each step height corresponding to a specific FP cavity length.

[0030] S2. Working mold replication process: Using the original mold obtained in step S1 as the master template, the pattern structure is transferred to the working mold material through nanoimprinting process to obtain a flexible nanoimprinting working mold.

[0031] S3. Lower reflective layer fabrication process: The lower reflective layer is fabricated on a transparent substrate using a thin film deposition process;

[0032] S4. Metasurface micro / nano structure forming process: A dielectric metasurface micro / nano structure is formed on the lower reflective layer by nanoimprinting and etching processes.

[0033] S5, FP cavity dielectric layer forming process: Using nanoimprinting technology, the dielectric layer with N preset thicknesses is formed in one step on the pre-formed metasurface micro / nano structure using the FP cavity working mold, thus forming a multi-cavity long FP cavity array.

[0034] S6. Upper reflective layer preparation process: An upper reflective layer is prepared on the surface of the dielectric layer using a thin film deposition process.

[0035] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0036] As a preferred technical solution of the present invention, step S4 specifically includes the following sub-steps:

[0037] S41, Functional material layer deposition: On the lower reflective layer, a functional medium material for forming a metasurface is deposited;

[0038] S42. Nanoimprinting patterning: Imprinting adhesive is coated on the functional material layer, and the metasurface working mold is used to imprint, cure, and demold, thereby replicating the metasurface nanostructure pattern onto the imprinting adhesive layer.

[0039] S43. Dry etching transfer: Using the cured imprinted adhesive layer as a mask, an anisotropic dry etching process is used to transfer the metasurface nanostructure pattern to the underlying functional medium material layer.

[0040] S44. Cleaning: Remove residual imprinting mask to obtain a clean dielectric metasurface micro / nano structure.

[0041] As a preferred technical solution of the present invention: step S5 specifically includes: coating a dielectric material for constituting the intermediate layer of the FP cavity onto the formed metasurface micro / nano structure, and using the FP cavity working mold to imprint, cure, and demold; the different step heights of the FP cavity working mold enable the dielectric material to form multiple preset thicknesses in different areas, directly constituting the dielectric layer structure of the multi-cavity long FP cavity.

[0042] As a preferred technical solution of the present invention: in step S1, the high-precision photolithography process is electron beam lithography; the dry etching process includes ion beam etching or inductively coupled plasma etching; the three-dimensional micro-nano fabrication process includes two-photon polymerization direct writing or grayscale exposure.

[0043] As a preferred technical solution of the present invention: in step S2, the working mold material includes PDMS, acrylate or epoxy resin; the nanoimprinting process includes UV curing imprinting or thermosetting imprinting.

[0044] Compared with the prior art, the multi-channel filter chip and its fabrication method of the present invention, which synergistically regulate FP cavity and metasurface, have the following beneficial effects:

[0045] This invention employs a dual-layer synergistic control mechanism of coarse tuning using FP cavities and fine tuning using metasurfaces: First, N preset thicknesses of the dielectric layer form N FP cavity units with different cavity lengths, dividing the target wavelength band into N sub-intervals for initial screening across the entire band. Then, within the region corresponding to each filter channel, uniform and monotonic variations in subwavelength nanostructure parameters ensure that the transmission wavelength is evenly distributed within its respective sub-interval, achieving fine tuning of the filter. Through this dual-layer control, this invention can form multiple narrowband filter channels (e.g., 49 or more) covering a wide wavelength band with a limited number of cavity lengths. This effectively solves the technical challenges of existing FP cavity arrays requiring a large number of different cavity lengths to cover a wide wavelength band, and the difficulty in achieving both high resolution and wide wavelength band coverage in metasurface filtering schemes, thus achieving a balance between wide-band coverage and high spectral resolution.

[0046] The transmission response of each filter channel in this invention satisfies a clear spectral reconstruction relationship with the incident spectrum. By pre-calibrating and obtaining the transmittance function of each channel, and combining it with the measured light intensity signal Ii of each channel, the incident spectrum S(λ) can be solved using a spectral reconstruction algorithm. This provides a complete data processing path in the practical application of the chip, ensuring high-fidelity recovery of spectral information.

[0047] This invention utilizes nanoimprint technology to construct a complete chip fabrication process. Through the preparation of the original mold, the replication of the flexible working mold, and one-time imprinting, it achieves low-cost, high-precision fabrication of metasurface structures and multi-cavity FP arrays. It effectively solves the triple technical challenges of existing FP arrays requiring a large number of different cavity lengths to cover a wide band, the difficulty in achieving both high resolution and wide band in metasurface filtering schemes, and the complexity, precision control difficulties, and high mass production costs of traditional micro-nano fabrication processes. It achieves the technical effects of unifying high spectral resolution and wide detection band, obtaining more than 49 narrowband channels with only a limited cavity length, simplifying the process flow and ensuring good cavity length consistency, and significantly reducing the manufacturing cost of a single chip. It provides a feasible technical path for the portable application and industrialization of miniature spectrometers in environmental monitoring, biomedical detection, and materials analysis.

[0048] This invention discloses a multi-channel filter chip and its fabrication method based on the synergistic control of Fabry-Perot (FP) microcavity array and metasurface for spectral filtering. This method is applicable to the 900-1700nm near-infrared band and can meet the research and development and production needs of miniature spectrometers in scenarios such as environmental monitoring, biomedical detection, and material analysis, and has great application prospects. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the layered structure of the spectrometer of the present invention.

[0050] In the attached diagram, 1 is the transparent substrate, 2 is the lower reflective layer, 3 is the metasurface micro / nano structure, 4 is the dielectric layer, and 5 is the upper reflective layer.

[0051] Figure 2 This is a graph showing the correspondence between the transmission response and spectral information of a single filter channel in the chip of this invention;

[0052] Figure 3 This invention relates to a method for manufacturing metasurface molds;

[0053] Figure 4 This invention relates to a method for manufacturing an FP cavity mold;

[0054] Figure 5 This invention relates to a method for manufacturing the working mold;

[0055] Figure 6 This is a schematic diagram of the processing technology of the present invention;

[0056] Figure 7 These are the simulation results for narrowband filtering using a 49-channel filter.

[0057] Figure 8 This is a spectral reconstruction. Detailed Implementation

[0058] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0059] like Figure 1 As shown, the multi-channel filter chip of the present invention, which is synergistically controlled by FP cavity and metasurface, provides a novel multi-channel filter chip that integrates metasurface and FP cavity. The chip consists of a transparent substrate 1, a lower reflective layer 2, a metasurface micro / nano structure 3, a dielectric layer 4, and an upper reflective layer 5 stacked from bottom to top.

[0060] The metasurface micro / nano structure is an arrayed subwavelength nanostructure disposed on the upper surface of the lower reflective layer; the dielectric layer covers the metasurface structure and has N preset thicknesses in different regions to form a multi-cavity long FP cavity array; the upper and lower reflective layers and the dielectric layer together constitute a complete FP cavity.

[0061] The chip encodes and modulates the spectrum using a combination of coarse tuning via a FP cavity and fine tuning via a metasurface. First, the target wavelength is divided into multiple sub-intervals by utilizing various thicknesses of the dielectric layer, achieving preliminary screening. Then, by adjusting the structural parameters of the metasurface, the transmission wavelength is continuously shifted within each sub-interval, thereby achieving high-density narrowband filtering covering a wide wavelength range with a limited cavity length.

[0062] The incident light is incident vertically from above the chip, filtered by the structure described above, and then exits from below the substrate.

[0063] The reflective layer can be made of Au, Ag, or a distributed Bragg reflector (DBR) composed of stacked high-refractive-index and low-refractive-index media. The metasurface micro / nanostructure is made of a high-refractive-index material. By arraying the metasurface micro / nanostructure and changing the structural parameters, filtering across different wavelengths can be achieved. Dielectric layer 4 uses photoresist such as SU-8 to protect the structure and form the intermediate cavity layer.

[0064] Spectral Reconstruction: Combinations of different cavity lengths and metasurface micro / nano structures encode the incident spectrum S(λ) into intensity signals for multiple channels. The transmittance function of the Ii-th filtered channel is Ti(λ). When used in conjunction with a photodetector with a spectral response Ei(λ), the measured intensity Ii satisfies...

[0065]

[0066] By obtaining Ti(λ) for all channels through pre-calibration or simulation, and after measuring Ii, the incident spectrum S(λ) can be solved using a reconstruction algorithm. The corresponding relationship is as follows: Figure 2 As shown.

[0067] The spectral modulation of this invention involves synergistic modulation of a FP cavity and a metasurface. Based on the target spectral range, the materials and thicknesses of the upper and lower reflective layers are determined, followed by coarse FP cavity tuning: the target wavelength is divided into multiple sub-intervals, each corresponding to a fixed FP cavity length; combinations of multiple cavity lengths achieve initial screening across the entire wavelength range. Fine tuning of the metasurface micro / nanostructure is then performed: for each sub-interval corresponding to the FP cavity length, the metasurface micro / nanostructure parameters, such as period and geometric parameters, are adjusted to shift the transmission wavelength. The correspondence between the transmission response of the filter element and the spectral information is as follows: Figure 2 As shown, the filter channel has high transmittance in the wavelength range of 900nm to 1100nm, while the transmittance drops sharply to near zero after 1200nm, exhibiting typical narrowband filtering characteristics.

[0068] The fabrication method of the multi-channel filter chip of the present invention, which is synergistically controlled by FP cavity and metasurface, includes the following steps:

[0069] S1. Original mold preparation process:

[0070] The original molds for the metasurface and the FP cavity were prepared separately.

[0071] The preparation of the metasurface original mold is achieved by using a high-precision photolithography process combined with a dry etching process to form a high aspect ratio subwavelength nanostructure on a hard substrate.

[0072] The original mold for the FP cavity is prepared by using three-dimensional micro-nano fabrication technology to form a three-dimensional structure with multiple different step heights on another substrate, with each step height corresponding to a specific FP cavity length.

[0073] S2. Working mold replication process:

[0074] Using the original mold obtained from S1 as a master template, the pattern structure is transferred to the working mold material through steps of applying glue, imprinting, curing, and demolding, resulting in a flexible and reusable nanoimprint working mold.

[0075] S3. Lower reflective layer fabrication process:

[0076] A lower reflective layer is fabricated on a transparent optical substrate using physical or chemical vapor deposition. This reflective layer can be a thin metal film or a distributed Bragg mirror composed of alternating high and low refractive index media.

[0077] S4. Metasurface micro / nano structure forming process:

[0078] This process uses nanoimprinting and etching techniques to form a dielectric metasurface on the planar reflective layer. The specific steps are as follows:

[0079] (1) Functional material layer deposition: A layer of functional medium material for forming metasurface is deposited on the lower reflective layer.

[0080] (2) Nanoimprinting patterning: Imprinting adhesive is coated on the functional material layer, imprinting is performed using a metasurface working mold, and curing is performed by ultraviolet exposure or heating. Then, the mold is removed. The metasurface nanostructure pattern is copied to the imprinting adhesive layer in the above way.

[0081] (3) Dry etching transfer: Using the cured imprinted adhesive layer as a mask, an anisotropic dry etching process is used to accurately transfer the metasurface nanostructure from the adhesive layer to the functional medium material layer below.

[0082] Cleaning: Remove residual imprinting mask to obtain a clean dielectric metasurface micro / nano structure.

[0083] S5, FP cavity dielectric layer forming process:

[0084] This process utilizes nanoimprinting to form a multi-cavity long FP-cavity array in a single step. The specific steps are as follows:

[0085] (1) Dielectric layer coating: Dielectric material is coated on the formed metasurface micro / nano structure to form the intermediate layer of the FP cavity.

[0086] (2) Nanoimprinting: The process involves three steps: imprinting, curing, and demolding, using an FP cavity working mold. The different step heights of the mold allow the dielectric material to form multiple preset thicknesses in different areas, thereby directly constituting the dielectric layer structure of a multi-cavity long FP cavity.

[0087] S6. Upper reflective layer preparation process:

[0088] On the surface of the dielectric layer with multi-cavity long FP cavity formed in S5, the same thin film deposition process as in S3 is used to prepare the upper reflective layer, which together with the lower reflective layer and the dielectric layer constitutes a complete FP cavity structure.

[0089] In step S1, the high-precision photolithography process is electron beam lithography. Dry etching processes include IBE and ICP etching. Three-dimensional micro / nano fabrication processes include two-photon polymerization direct writing and grayscale exposure.

[0090] In step S2, the working mold material includes PDMS, acrylate, and epoxy resin.

[0091] Step S4, the functional medium material is silicon nitride, amorphous silicon, or silicon carbide.

[0092] Example 1

[0093] Material and design parameter selection for the multi-channel filter chip with synergistic modulation of FP cavity and metasurface in this invention: Considering the light intensity loss and process compatibility of the entire FP cavity, materials with low extinction coefficients and easy processing are selected for the target wavelength band. The material selection is as follows: DBR reflective layer material: silicon dioxide (SiO2) and amorphous silicon (a-Si). Transparent substrate: quartz glass. FP cavity intermediate layer material: SU-8 photoresist. Metasurface functional material: amorphous silicon.

[0094] The design of the DBR reflective layer in this invention:

[0095] Based on the λ / 4 optical thickness principle, a DBR composed of two pairs of alternating SiO2 and a-Si layers was designed. The a-Si layer thickness was designed to be 85 nm, and the SiO2 layer thickness was 200 nm. This design can form a high-reflection region in the center of the target wavelength band, while avoiding the problems of excessively narrow transmission peaks and low transmission intensity caused by too many layers.

[0096] The present invention relates to the design of multi-cavity length FP cavity parameters for a multi-channel filter chip with synergistic modulation of FP cavity and metasurface: the 900-1700nm wavelength band is initially divided into several sub-intervals. Based on the FP cavity resonance condition nL=mλ / 2, where n is the SU-8 refractive index, L is the cavity length, and m is the interference order, the design thickness range of the SU-8 dielectric layer is determined to be approximately 250-750nm, and a fixed design cavity length is assigned to each sub-interval.

[0097] The metasurface design of the multi-channel filter chip with FP cavity and metasurface synergistic control in this invention:

[0098] To achieve fine-tuning, the metasurface was designed as a periodic array of a-Si nanocylinders. With a fixed period P = 400 nm and a height H = 200 nm, by uniformly varying the diameter D within the range of 100-300 nm, the resonance peak of the metasurface can be continuously shifted within its respective FP cavity subband. As the diameter increases, the resonance peak shifts to longer wavelengths.

[0099] The optical field simulation verification of the multi-channel filter chip of the present invention, which is synergistically controlled by the FP cavity and metasurface, was performed using the finite-difference time-domain (FDTD) method. By combining different cavity lengths L and nanopillar diameters D, 49 different sets of structural parameters were optimized. The 49 transmission spectrum curves extracted from the simulation are shown below. Figure 7 As shown, they serve as 49 narrowband filter channels, covering the target wavelength range of 900-1700nm.

[0100] The spectral reconstruction simulation verification of the multi-channel filter chip synergistically controlled by the FP cavity and metasurface of this invention: Based on the above 49 simulated transmission responses Ti(λ) and typical CMOS detector responses Ei(λ), the measurement process of different incident spectra S(λ) was simulated. By introducing random noise to simulate the actual measured value Ii, and using the reconstruction algorithm to successfully retrieve the original spectrum, the effectiveness of the system was verified. The simulation results are as follows: Figure 8 As shown.

[0101] The method for fabricating the multi-channel filter chip with FP cavity and metasurface synergistic control of the present invention specifically implements the fabrication methods described in steps S1-S6:

[0102] Step S1: Initial Mold Preparation: For the metasurface initial mold: Electron beam photoresist is spin-coated onto a silicon substrate. The designed nanopillar array pattern is exposed using an electron beam direct writing device, and after development, the photoresist pattern is formed. Subsequently, a 50nm Cr layer is sputtered, and a Cr hard mask is formed through a lift-off process. Finally, using the Cr mask, the silicon substrate is etched using an ICP dry etching process to obtain a high aspect ratio metasurface structure mold. The process is as follows: Figure 3 As shown in the ad.

[0103] FP cavity mold: Two-photon polymerized photoresist is coated on the surface of a quartz or silicon substrate. A pre-designed multi-step height file and alignment marks are loaded into a two-photon polymerized direct-write device, and the wafer is exposed. After exposure, development is performed to remove material from unexposed areas, forming the required three-dimensional FP cavity structure mold. The process is as follows: Figure 4 As shown in ac.

[0104] Step S2: Working Mold Fabrication: Spin-coat polydimethylsiloxane working mold adhesive onto the surface of the original mold at 2000 rpm; then cover the adhesive with a PET film; cure the mold adhesive by irradiation with a UV lamp for 180 seconds; finally, peel the cured working mold along with the PET film from the original mold to obtain a flexible working mold for nanoimprinting. The process is as follows: Figure 5 As shown in the ad.

[0105] Perform S3: Lower Reflective Layer Preparation: Prepare a flat quartz glass substrate and clean it. Using a plasma-enhanced chemical vapor deposition (PECVD) system, deposit a-Si and SiO2 layers sequentially according to the design in Section 4.2 to form the lower DBR.

[0106] Step S4: Metasurface Structure Forming: A 200nm amorphous silicon layer is deposited on the lower DBR layer as the functional material layer for subsequent metasurface formation. A layer of UV-curable nanoimprint liner (E30 liner) is spin-coated onto the deposited amorphous silicon layer at 2000rpm, followed by pre-baking on an 80°C hot plate for 30 seconds. The prepared metasurface working mold is aligned and pressed against the liner surface, and the liner is cured by UV exposure for 300 seconds. After curing, the working mold is demolded, and the metasurface nanostructure pattern is transferred to the liner layer.

[0107] Subsequently, reactive ion beam etching was employed, using the cured imprinted resist layer as a mask to etch the underlying amorphous silicon layer. A combination of SF6 (30 sccm) and C4F8 (40 sccm) was used as the etching gas, with an inductively coupled plasma power of 1000 W and an RF bias power of 80 W. By controlling the etching time, the metasurface micro / nanostructure morphology on the imprinted resist was completely transferred to the amorphous silicon layer. After etching, oxygen plasma was used to remove the residual imprinted resist mask, yielding the amorphous silicon metasurface structure.

[0108] S5: FP cavity dielectric layer formation: After surface cleaning of the formed metasurface sample, a tackifier is spin-coated at 2000 rpm, heated to 120°C for 180 s, followed by spin-coating of SU-8 photoresist. Alignment, imprinting, and UV exposure are then performed using the FP cavity working mold obtained in S2. After curing, the mold is removed, and the SU-8 adhesive layer forms a dielectric layer of various thicknesses with a 4.3-section design, constituting a multi-cavity long FP cavity array.

[0109] Perform S6: Upper reflective layer preparation: Place the sample into the PECVD equipment and deposit two pairs of SiO2 / a-Si thin films on the surface of the SU-8 dielectric layer using the same process and parameters as the upper DBR deposition to form the upper DBR reflector.

[0110] This invention proposes a filter chip scheme combining FP cavities and metasurfaces. Using a smaller number of FP cavity lengths, it can achieve tens or even hundreds (several times the number of cavity lengths) of narrowband filtering spectral channels within a wide wavelength range of 900-1700 nm, thus facilitating simultaneous high-resolution and wide-band spectral detection. Furthermore, for this filter chip, this invention also proposes a novel nanoimprint-based fabrication method. The nanoimprint process not only enables the patterning of metasurface nanostructures but also allows for the one-time molding of FP cavity arrays of different cavity lengths, making low-cost mass production of this spectral tuning chip possible.

[0111] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A multi-channel filter chip with FP cavity and metasurface synergistic modulation, characterized in that, The transparent substrate, lower reflective layer, metasurface micro / nano structure, dielectric layer, and upper reflective layer are stacked sequentially from bottom to top. The metasurface micro / nano structure is an array of subwavelength nanostructures. Within a region corresponding to a filter channel, the structural parameters of the subwavelength nanostructures exhibit uniform and monotonic variation, and the transmission wavelengths are evenly distributed within the corresponding sub-intervals, enabling fine-tuning of filtering in different bands. The dielectric layer has N preset thicknesses in different regions, forming N FP cavity units with different cavity lengths, which correspond to N filter channels respectively; The upper reflective layer, together with the lower reflective layer and the dielectric layer, constitutes the FP cavity structure; The FP cavity and the metasurface micro / nano structure work together to modulate the incident spectrum: the N preset thicknesses of the dielectric layer divide the target wavelength band into N sub-intervals, achieving preliminary screening across the entire wavelength band; by adjusting the structural parameters of the subwavelength nanostructures corresponding to each region, the transmission wavelength of each filter channel is continuously shifted within its respective sub-interval, thus forming narrowband filter channels covering a wide wavelength band with different preset values ​​corresponding to a limited number of cavity lengths; the transmission response of each filter channel satisfies the following relationship with the incident spectrum: Where i represents the channel number, λ represents the wavelength, λ2 is the longest wavelength of the working band, λ1 is the starting wavelength of the working band, and I i Let S(λ) be the light intensity signal acquired by the i-th channel, and E be the incident spectrum. i (λ) is the spectral response function of the photodetector, T i (λ) is the transmittance function of the i-th channel; the transmittance functions T of all channels are obtained through pre-calibration. i (λ), and combined with the acquired light intensity signal I i The incident spectrum S(λ) can then be solved using a spectral reconstruction algorithm.

2. The multi-channel filter chip with FP cavity and metasurface synergistic control as described in claim 1, characterized in that, The lower and upper reflective layers are either metallic reflective layers or distributed Bragg reflectors. The metal reflective layer is made of Au or Ag material; The distributed Bragg reflector is composed of alternating stacks of high-refractive-index and low-refractive-index media materials.

3. The multi-channel filter chip with FP cavity and metasurface synergistic control as described in claim 1, characterized in that, The material of the metasurface micro / nanostructure is a high refractive index medium material, including silicon nitride, amorphous silicon, or silicon carbide; the metasurface micro / nanostructure is a nanopillar array, a nanopore array, or a nanofin array, and its structural parameters include period, diameter, width, or height.

4. The multi-channel filter chip with FP cavity and metasurface synergistic control as described in claim 1, characterized in that, The metasurface micro / nanostructure is a periodic a-Si nanocylindrical array with a fixed period P=400nm and a height H=200nm. By uniformly varying the diameter D within the range of 100-300nm, the resonance peak of the metasurface micro / nanostructure is continuously shifted within its respective FP cavity sub-band. As the diameter increases, the resonance peak shifts towards longer wavelengths.

5. The multi-channel filter chip with FP cavity and metasurface synergistic control as described in claim 1, characterized in that, The material of the dielectric layer is photoresist, including SU-8 photoresist.

6. The multi-channel filter chip with FP cavity and metasurface synergistic control as described in claim 1, characterized in that, The target wavelength is the 900-1700nm near-infrared band; the preset thickness range of the dielectric layer is 250-750nm; the metasurface micro / nano structure is a periodic amorphous silicon nanocylindrical array with a period of 400nm, a height of 200nm, and a diameter that varies in the range of 100-300nm.

7. A method for fabricating a multi-channel filter chip with synergistic modulation of FP cavity and metasurface as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Initial mold fabrication process: The initial mold for the metasurface and the initial mold for the FP cavity are fabricated separately. The initial mold for the metasurface is formed on a hard substrate using a combination of high-precision photolithography and dry etching. The initial mold for the FP cavity is formed on a substrate using a three-dimensional micro-nano fabrication process, which forms a three-dimensional structure with multiple different step heights, each step height corresponding to a specific FP cavity length. S2. Working mold replication process: Using the original mold obtained in step S1 as the master template, the pattern structure is transferred to the working mold material through nanoimprinting process to obtain a flexible nanoimprinting working mold. S3. Lower reflective layer fabrication process: The lower reflective layer is fabricated on a transparent substrate using a thin film deposition process; S4. Metasurface micro / nano structure forming process: A dielectric metasurface micro / nano structure is formed on the lower reflective layer by nanoimprinting and etching processes. S5, FP cavity dielectric layer forming process: Using nanoimprinting technology, the dielectric layer with N preset thicknesses is formed in one step on the pre-formed metasurface micro / nano structure using the FP cavity working mold, thus forming a multi-cavity long FP cavity array. S6. Upper reflective layer preparation process: An upper reflective layer is prepared on the surface of the dielectric layer using a thin film deposition process.

8. The method for fabricating a multi-channel filter chip with synergistic modulation of FP cavity and metasurface as described in claim 7, characterized in that, Step S4 specifically includes the following sub-steps: S41, Functional material layer deposition: On the lower reflective layer, a functional medium material for forming a metasurface is deposited; S42. Nanoimprinting patterning: Imprinting adhesive is coated on the functional material layer, and the metasurface working mold is used to imprint, cure, and demold, thereby replicating the metasurface nanostructure pattern onto the imprinting adhesive layer. S43. Dry etching transfer: Using the cured imprinted adhesive layer as a mask, an anisotropic dry etching process is used to transfer the metasurface nanostructure pattern to the underlying functional medium material layer. S44. Cleaning: Remove residual imprinting mask to obtain a clean dielectric metasurface micro / nano structure.

9. The method for fabricating a multi-channel filter chip with synergistic modulation of FP cavity and metasurface as described in claim 7, characterized in that, Step S5 specifically includes: coating the formed metasurface micro / nano structure with a dielectric material for forming the intermediate layer of the FP cavity, and using the FP cavity working mold to imprint, cure, and demold; the different step heights of the FP cavity working mold allow the dielectric material to form multiple preset thicknesses in different areas, directly forming the dielectric layer structure of the multi-cavity long FP cavity.

10. The method for fabricating a multi-channel filter chip with synergistic modulation of FP cavity and metasurface as described in claim 7, characterized in that, In step S2, the working mold material includes PDMS, acrylate, or epoxy resin; the nanoimprinting process includes UV curing imprinting or thermosetting imprinting.

Images