Narrowband filter based on micro-nano grating, spectrum chip and imaging method

Abstract

The invention discloses a narrow-band filter based on a micro-nano grating, a spectrum chip and an imaging method, and belongs to the field of optical filters, the narrow-band filter comprises a dielectric layer, a metal grating layer and a substrate which are sequentially stacked from top to bottom, the dielectric layer covers the top of the metal grating layer and is wrapped between metal grating lines of the metal grating layer, and the metal grating layer covers the substrate. The thickness of the dielectric layer is 3000nm, the thickness of the metal grating layer is 40nm, and the distance between adjacent metal grating lines of the metal grating layer is 120nm; metal grating lines of the metal grating layer form periodic structures according to a periodic rule, one periodic structure forms a channel with one filter unit corresponding to one specific wavelength, multi-band spectral information is separated by selectively transmitting light with the specific wavelength, and all the periodic structures jointly form a narrow-band filter array. According to the invention, an artificial microstructure is adopted to realize a pixel-level light splitting effect, and the volume of a hyperspectral imaging system can be obviously reduced.

Description

Technical Field

[0001] The present invention relates to the field of filters, and particularly to a narrowband filter based on micro-nano gratings, a spectral chip, and an imaging method. Background Art

[0002] The information contained in the infrared spectrum is extremely rich. The infrared spectrum can be used to distinguish chemical bonds, functional groups, etc. of substances. At the same time, in the near-infrared band, different substances also have significantly different absorption and reflection spectra. Near-infrared spectrum detection is also extremely important for the screening and detection of substances. Spectrometers are usually difficult to fabricate, large in size, and expensive. Compared with spectrometers, hyperspectral detectors have advantages such as low cost and high integration, and have good spectral resolution, which is one of the important development directions of spectral detection systems. The research and development of infrared hyperspectral detectors is the key to realizing the innovation of infrared spectral imaging technology and can be used for the discrimination of different substances. Compared with conventional photodetectors, infrared hyperspectral detectors can obtain richer, more accurate, and more reliable physical and chemical information of the target, improving the recognition degree of the target. Traditional hyperspectral imagers consist of two parts: an infrared detector and a pointing mirror. Usually, the system is relatively complex and has low integration. Summary of the Invention

[0003] One object of the present invention is to provide a narrowband filter based on micro-nano gratings to solve the problems of the existing hyperspectral imager being relatively complex and having low integration.

[0004] The present invention is achieved through the following technical solutions. A narrowband filter based on micro-nano gratings, the narrowband filter includes a dielectric layer, a metal grating layer, and a substrate stacked in sequence from top to bottom. Among them, the dielectric layer covers the top of the metal grating layer and is coated between adjacent metal grating lines of the metal grating layer. The thickness of the dielectric layer is 3000 nm, the thickness of the metal grating layer is 40 nm, and the distance between adjacent metal grating lines of the metal grating layer is 120 nm; the metal grating lines of the metal grating layer form a periodic structure according to a periodic rule. One periodic structure forms a filter unit corresponding to a channel of a specific wavelength. By selectively transmitting light of a specific wavelength, multi-band spectral information is separated. All periodic structures together form a narrowband filter array.

[0005] Further, the material of the dielectric layer is SU8 photoresist.

[0006] Further, the material of the metal grating layer is Au.

[0007] Further, the periodic rule is p = w + 120 nm, where w is the width of the metal grating line and p is the width of the periodic structure. By adjusting the width of the periodic structure, the modulation of narrowband filtering is realized.

[0008] Further, the substrate is one of fused quartz glass, soda-lime glass, sapphire, silicon nitride, magnesium aluminate spinel, and polyimide film.

[0009] On the other hand, the present invention provides a narrowband filtering spectral chip based on a micro-nano grating, which includes, from top to bottom, the narrowband filter based on a micro-nano grating as described above, a photoelectric detection chip, and a readout circuit stacked in sequence. Among them, the photoelectric detection chip and the readout circuit are connected by a flip-chip interconnection process. The electrical contact surface of the photoelectric detection chip faces the readout circuit, and the photoelectric detection chip and the readout circuit are connected together through a flip-chip interconnection structure; the readout circuit is responsible for signal reading and processing, further amplifying, filtering, and digitizing the electrical signal converted by the photoelectric detection chip, and outputting data.

[0010] Further, the photoelectric detection chip is composed of InGaAs detection units. Each InGaAs detection unit is aligned with the filter unit on the narrowband filter, and is used to receive the light transmitted through the narrowband filter and convert it into an electrical signal; the pixel size of the InGaAs detection unit is 15 µm.

[0011] The present invention also provides an imaging method for a narrowband filtering spectral chip based on a micro-nano grating. The imaging method includes using a push-broom mode to collect signals of the narrowband filtering spectral chip based on a micro-nano grating as described above row by row. Each row represents a filter unit, and each filter unit receives different wavelength signals. The wavelength signals collected in each row are separately extracted to form independent channel data; each row works independently, detects and outputs the optical signal of its specific wavelength, and by accumulating the data during the push-broom process, the data of each column is extracted to form hyperspectral imaging.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0013] 1. The present invention uses artificial microstructures to achieve pixel-level spectral splitting effects, changing the mode of traditional hyperspectral spectrometers that require complex optical paths and gratings. At the same time, based on subwavelength micro-nano photon structures of metals and organic polymers, a narrowband spectral splitting array and its integration with a detector array are realized for an infrared hyperspectral detector.

[0014] 2. The hyperspectral imaging system of the present invention can avoid using the spectral splitting structures of traditional prisms and gratings, and realizes the narrowband filtering function through a metasurface structure, which can significantly reduce the volume and mass of the hyperspectral imaging system, improve the integration of the entire spectral imaging system, and thus achieve volume reduction and mass reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0016] Figure 1 Schematic diagram of the narrowband filter structure provided in Embodiment 1 of the present invention.

[0017] Figure 2 Schematic sectional view of the narrowband filter provided in Embodiment 1 of the present invention.

[0018] Figure 3 Schematic diagram of the narrowband filter spectral chip structure provided in Embodiment 2 of the present invention. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0020] Embodiment 1

[0021] This embodiment discloses a narrowband filter based on a micro-nano grating. Figure 1 The schematic diagram of the narrowband filter structure in this embodiment is shown. Figure 2 The schematic sectional view of the narrowband filter in this embodiment is shown. In the figure, a represents the metal grid line, b represents the dielectric layer, c represents the substrate, p is the width of the periodic structure, and w is the width of the metal grid line.

[0022] It can be seen from the figure that the narrowband filter includes, from top to bottom, a dielectric layer, a metal grating layer, and a substrate stacked in sequence.

[0023] Among them, the dielectric layer covers the top of the metal grating layer and is wrapped between the metal grid lines of the metal grating layer. The thickness of the dielectric layer is 3000 nm, and the material of the dielectric layer is SU8 photoresist.

[0024] The thickness of the metal grating layer is 40 nm, and the distance between adjacent metal grid lines of the metal grating layer is 120 nm.

[0025] In this embodiment, Au is selected as the material of the metal grating layer.

[0026] The metal grid lines of the metal grating layer form a periodic structure according to the periodic rule. One periodic structure forms a filter unit corresponding to a channel of a specific wavelength. By selectively transmitting light of a specific wavelength, multi-band spectral information is separated. All the periodic structures together constitute a narrowband filter array.

[0027] Specifically, the period rule of the periodic structure is p = w + 120 nm, where w is the width of the metal grating line and p is the width of the periodic structure. By adjusting the width of the periodic structure, the modulation of narrowband filtering can be achieved.

[0028] It should be noted that the metal grating lines and their arrangement form a periodic structure. These grating lines are arranged with specific widths and spacings, which are called periods. Figure 2 In the cross-sectional view, the width w of the metal grating line and the spacing of 120 nm are marked, forming a repeating structure with a period of p = w + 120 nm. The period p can be adjusted by changing the width w of the metal grating line, thereby achieving the modulation of narrowband filtering.

[0029] A filtering channel is formed with each group of periodic structures as a unit. Each channel can be composed of multiple periodic structures. Each channel corresponds to a specific filtering range, and the transmission wavelength of each channel can be regulated by designing different widths w of the metal grating lines. Different channels are designed with different periodic structures to achieve the separation and detection of spectra in different bands.

[0030] In this embodiment, quartz glass is selected as the substrate. In other embodiments, soda-lime glass, sapphire, silicon nitride, magnesium aluminate spinel, or polyimide film can also be used as the substrate.

[0031] Finally, a narrowband filter based on micro-nano gratings is prepared.

[0032] Example 2

[0033] Based on the narrowband filter prepared in Example 1, this embodiment provides a narrowband filtering spectral chip based on micro-nano gratings. Figure 3 The structural schematic diagram of the narrowband filtering spectral chip in this embodiment is shown. In the figure, A represents the narrowband filter prepared in Example 1, B represents the photoelectric detection chip, and C represents the readout circuit.

[0034] As can be seen from the figure, the narrowband filtering spectral chip includes, from top to bottom, a narrowband filter layer, a photoelectric detection chip layer, and a readout circuit layer stacked in sequence.

[0035] Among them, the photoelectric detection chip is composed of multiple InGaAs detection units. Each InGaAs detection unit is aligned with the filter unit on the narrowband filter and is used to receive the light transmitted through the narrowband filter and convert it into an electrical signal. The pixel size of the InGaAs detection unit selected in this embodiment is 15 µm.

[0036] The optoelectronic detection chip and the readout circuit are connected by a flip-chip interconnection process. The electrical contact surface of the optoelectronic detection chip faces the readout circuit and is connected together through solder balls, thus ensuring the efficient transmission of detection signals from the optoelectronic detection chip to the readout circuit;

[0037] The readout circuit is responsible for signal reading and processing, further amplifying, filtering, and digitizing the electrical signals converted by the optoelectronic detection chip, and outputting data.

[0038] Example 3

[0039] In this example, an imaging method for a narrowband filtering spectral chip based on a micro-nano grating is provided. The imaging method in this embodiment is used to perform imaging based on the data generated by the narrowband filtering spectral chip based on the micro-nano grating in Example 2. The steps are as follows:

[0040] Use the push-broom mode to control the readout circuit to collect the signals of the optoelectronic detection chip row by row. Each row represents a filter unit, and each filter unit receives different wavelength signals. The wavelength signals collected in each row are separately extracted to form independent channel data. Finally, the data in each column is extracted to constitute hyperspectral imaging

[0041] It should be noted that since each filter unit receives signals of a specific wavelength, "each column" can represent a combination of different wavelength signals. For example, in a two-dimensional detector array, each column may contain the accumulation of different wavelength information, or each column is related to the spatial position of the imaging area. Therefore, extracting data column by column may help to form a hyperspectral data set, and the data in each column represents spectral signals from different bands.

[0042] In the push-broom mode, the sensor or imaging system scans along one direction (usually the row direction) of the sample and collects data row by row. The extraction of column data is actually carried out through the spatial structure of the scanning area. For example, when the scanner pushes and scans in a certain direction, each column of the detector array will receive different spectral information from different spatial positions. Each column may represent a different imaging area or a different wavelength channel in this context.

[0043] Hyperspectral imaging requires obtaining a large amount of spectral data. Therefore, in the push-broom mode, the scanning device needs to collect data at different positions (columns) by means of push-broom (row-by-row scanning). These data are organized into a two-dimensional spectral data set, where each column represents a specific wavelength channel and forms a complete hyperspectral image after processing. The push-broom method makes it possible to collect data row by row and column by column, so as to distinguish different spectral information according to spatial position and wavelength.

[0044] The imaging method in this embodiment utilizes the cooperation between the narrowband filter and the photoelectric detection unit in Embodiment 2. By controlling the readout circuit to collect and process optical signals of different wavelengths line by line in the push-broom mode, it can achieve efficient collection and processing of spectral information. Finally, by accumulating the results of multiple lines, hyperspectral data is generated to achieve high-precision spectral imaging.

[0045] The specific embodiments described above further elaborate on the object, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A narrowband filter based on micro-nano gratings, characterized in that, The narrowband filter includes, from top to bottom, a dielectric layer, a metal grating layer, and a substrate stacked in sequence, where the dielectric layer covers the top of the metal grating layer and is coated between adjacent metal grating lines of the metal grating layer, and the thickness of the dielectric layer is 3000 nm. The thickness of the metal grating layer is 40 nm, and the pitch between adjacent metal grating lines of the metal grating layer is 120 nm. The metal grating lines of the metal grating layer form a periodic structure according to a periodic rule. One periodic structure forms a filter unit, and one filter unit corresponds to a channel of a specific wavelength. By selectively transmitting light of a specific wavelength, multi-band spectral information is separated, and all the periodic structures together form a narrowband filter array.

2. The narrowband filter based on a micro-nano grating according to claim 1, characterized in that The material of the dielectric layer is SU8 photoresist.

3. The narrowband filter based on a micro-nano grating according to claim 1, characterized in that, The material of the metal grating layer is Au.

4. The narrowband filter based on a micro-nano grating according to claim 1, characterized in that, The cycle rule is p = w +120 nm , where w is the width of the metal gate line, p is the width of the periodic structure, and the modulation of narrowband filtering is achieved by adjusting the width of the periodic structure.

5. The narrowband filter based on a micro-nano grating according to claim 1, characterized in that The substrate is one of quartz glass, soda-lime glass, sapphire, silicon nitride, magnesium aluminate spinel, and polyimide film.

6. A narrowband filtering spectral chip based on micro-nano gratings, characterized in that, The spectral chip includes, from top to bottom, a narrowband filter based on micro-nano gratings as described in any one of claims 1 to 5, an optoelectronic detection chip, and a readout circuit stacked in sequence, where the optoelectronic detection chip and the readout circuit are connected by a flip-chip interconnection process. The electrical contact surface of the optoelectronic detection chip faces the readout circuit, and the optoelectronic detection chip and the readout circuit are connected together through a flip-chip interconnection structure. The readout circuit is responsible for signal reading and processing, further amplifying, filtering, and digitizing the electrical signals converted by the optoelectronic detection chip, and outputting data.

7. The narrowband filtering spectral chip based on a micro-nano grating according to claim 6, characterized in that, The optoelectronic detection chip is composed of InGaAs detection units. Each InGaAs detection unit is aligned with the filter unit on the narrowband filter, and is used to receive the light transmitted through the narrowband filter and convert it into an electrical signal. The pixel size of the InGaAs detection unit is 15 µm .

8. An imaging method for a narrowband filtering spectral chip based on micro-nano gratings, characterized in that, The imaging method includes using a push-broom mode to collect signals row by row for the narrowband filtering spectral chip based on micro-nano gratings as described in any one of claims 6 to 7. Each row represents a filter unit, and each filter unit receives different wavelength signals. The wavelength signals collected in each row are separately extracted to form independent channel data. Each row works independently, detects and outputs the optical signal of its specific wavelength. By accumulating the data during the push-broom process and extracting the data of each column therefrom, hyperspectral imaging is formed.

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