A high-resolution high-throughput near-infrared on-chip spectrometer based on dielectric metasurface encoder

Abstract

The application discloses a high-resolution high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder, which comprises a dielectric metasurface encoder for encoding spectral information of incident light and a COMS image sensor. The spectral resolution of the spectrometer reaches 0.7 nm by optimizing the structural parameters and array arrangement of the metasurface unit, which can effectively distinguish adjacent narrow-band spectral lines and perform high-precision spectral detection. The dielectric metasurface encoder adopts a diatomic structure design, breaks the translational symmetry, excites a high-Q mode, blocks only the incident light of a specific wavelength, transmits all the rest of the incident light, maximizes the extraction efficiency of light energy, significantly improves the light flux, and enables high-precision detection in a weak light environment. The dielectric metasurface encoder adopts a diatomic structure design and has C4v symmetry, which is independent of the polarization state of the incident light and does not need to additionally configure a polarizer.

Description

Technical Field

[0001] This invention relates to the field of optical spectroscopy detection technology, and in particular to a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder. Background Technology

[0002] As a core optical instrument capable of decomposing polychromatic light into spectra and detecting them, spectrometers play an irreplaceable role in scientific research and industrial production. With the increasing demand for on-site detection and real-time monitoring, traditional large spectrometers, due to their large size, high cost, and reliance on professional laboratory environments, can no longer meet diverse application scenarios. Against this backdrop, miniaturization strategies have been applied to spectrometers, and on-chip spectrometers, as a typical strategy, have attracted much attention due to their extremely small space occupancy and excellent detection performance.

[0003] Currently, the mainstream on-chip spectrometers mainly adopt the dielectric metasurface encoder technology. These designs mostly use a bandpass strategy, which is essentially "single-wavelength selective reception". The dielectric metasurface encoder can only capture the energy of a very small portion of the wavelengths in the incident light. Most of the light energy is blocked by the filter, resulting in severe light flux loss and low sensitivity, which greatly limits the application range of on-chip spectrometers.

[0004] In addition, there are many on-chip spectrometers that can be used for near-infrared detection, but most of them have a detection range of only tens of nanometers in the infrared band, which cannot meet the needs of daily spectral detection. Even if a few solutions can achieve infrared spectral detection of hundreds of nanometers, their spectral resolution is usually only a dozen nanometers, making it difficult to perform high-precision measurements.

[0005] Therefore, how to provide a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] One objective of this invention is to provide a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder, which solves the problems mentioned in the background art.

[0007] According to an embodiment of the present invention, a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder includes a dielectric metasurface encoder for encoding spectral information of incident light; a CMOS image sensor for receiving the spectral information encoded by the dielectric metasurface encoder; and a signal processing module for solving the inverse problem corresponding to the encoding of the dielectric metasurface encoder to reconstruct the spectral information of the incident light.

[0008] The dielectric metasurface encoder is composed of It consists of metasurface units.

[0009] The metasurface unit is a TiO2 thin film 8 etched with a first square nanopore and a second square nanopore array. The first square nanopore and the second square nanopore array are arranged in a square lattice. Each lattice is a unit cell. Each unit cell is a diatomic structure and contains two first square nanopores with side lengths of L1 and L2, respectively.

[0010] The TiO2 thin film is deposited on the SiO2 substrate, which is fully compatible with the process of the CMOS image sensor and is directly integrated on the surface of the CMOS image sensor to form a system-on-a-chip.

[0011] The diatomic structure of the unit cell disrupts its translational symmetry, generating a high-Q mode. The diatomic structure of the unit cell retains its C4v symmetry, making the diatomic structure of the unit cell independent of the polarization state of the incident light, thus eliminating the need for an additional polarizer.

[0012] The period P of the unit cell determines the operating wavelength of the high-Q mode.

[0013] Each metasurface unit employs a cell with a different period to enable the high-Q mode operating wavelength to cover the operating range of the high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder.

[0014] The high-Q mode has a single-mode coverage of 5 times the wavelength range in the near-infrared band compared to the visible light band, making it suitable for near-infrared spectral detection.

[0015] The high-Q mode has a narrow-band response with a linewidth of 2 nm in the near-infrared band, ensuring high spectral resolution.

[0016] The high-Q mode only blocks incident light of a specific wavelength and transmits incident light of all other wavelengths, maximizing the extraction efficiency of light energy and ensuring high light flux.

[0017] The beneficial effects of this invention are: By optimizing the structural parameters and array arrangement of the metasurface units, the spectrometer achieves a spectral resolution of 0.7 nm (based on the Rayleigh criterion), effectively distinguishing adjacent narrowband spectral lines and enabling high-precision spectral detection.

[0018] The dielectric metasurface encoder adopts a dual-atom structure design, which breaks translational symmetry and excites a high-Q mode. This mode only blocks incident light of a specific wavelength and transmits incident light of all other wavelengths, maximizing the extraction efficiency of light energy and significantly improving the light flux, enabling it to perform high-precision detection even in low-light environments.

[0019] The dielectric metasurface encoder adopts a two-atom structure design with C4v symmetry, which is independent of the polarization state of the incident light and does not require an additional polarizer. This not only simplifies the overall structure of the spectrometer and reduces the size of the device, but also avoids the light energy loss caused by the polarizer, further improving the weak light detection capability.

[0020] The core material (SiO2) and processing technology (electron beam lithography, thin film deposition, etc.) of the dielectric encoder are fully compatible with the CMOS standard manufacturing process, and can be integrated on-chip with CMOS image sensors. This compatibility enables the spectrometer to be produced using semiconductor mass production technology, which greatly reduces manufacturing costs and makes its commercial promotion and widespread application possible.

[0021] Because the dielectric encoder is directly integrated with the CMOS image sensor, there is no need for complex spectroscopic components (such as gratings, lens groups, etc.), which greatly reduces the overall size of the spectrometer and significantly improves its portability. At the same time, its high sensitivity and high resolution characteristics enable it to meet diverse application needs, including but not limited to: nanoscale biospectral analysis, weak light fluorescence detection in medical diagnosis, astronomical spectroscopic detection, and Raman spectroscopy research, etc., and it is especially suitable for on-site detection scenarios without professional laboratory support. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall structure of a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder proposed in this invention.

[0023] Figure 2 This is a schematic diagram of the metasurface unit that makes up the dielectric metasurface encoder in a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder proposed in this invention.

[0024] Figure 3 This is a calibration curve of some metasurface units in a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder proposed in this invention.

[0025] Figure 4 This is a schematic diagram of the Q factor and light flux structure of the calibration curve in a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder proposed in this invention.

[0026] Figure 5 This is a comparison of the bimodal spectral measurement results of a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder proposed in this invention.

[0027] Figure 6 This is a comparison chart of broadband measurement results of a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder proposed in this invention.

[0028] Reference numerals: 1. Dielectric metasurface encoder; 2. CMOS image sensor; 3. Metasurface unit; 4. Signal processing module; 5. Unit cell; 6. First square nanopore; 7. Second square nanopore; 8. TiO2 thin film; 9. SiO2 substrate. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0030] refer to Figures 1-6 In this embodiment, a high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder, such as... Figure 1 As shown, it includes a dielectric metasurface encoder 1, a CMOS image sensor 2, and a signal processing module 4.

[0031] Dielectric metasurface encoder 1 is composed of The dielectric metasurface encoder 1 is composed of 196 metasurface units 3, which are used to encode the spectral information of the incident light. In this embodiment, the dielectric metasurface encoder 1 is composed of an array of 196 metasurface units 3, which are arranged in a 14×14 manner.

[0032] Metasurface unit 3 and cell structure such as Figure 2 As shown, in this embodiment, the two-atom structure of cell 5 adopts two first square nanopores 6 with side lengths of 60 nm and second square nanopores 7 with side lengths of 120 nm. The metasurface unit 3 is a TiO2 film 8 with two nanopore arrays (first square nanopore 6 and second square nanopore 7 with side lengths of 120 nm) etched on it. The TiO2 film 8 is deposited on SiO2 substrate 9 with a film thickness H of 90 nm. The preparation process includes: depositing TiO2 film 8 on SiO2 substrate 9 by electron beam evaporation, and forming two nanopore arrays on TiO2 film 8 by electron beam lithography (EBL), ion beam etching (IBE) and inductively coupled plasma (ICP) etching processes, and patterning with ARP photoresist, Cr:Au layer and amorphous silicon (α-Si) three-layer mask.

[0033] The diatomic structure of cell 5 disrupts its translational symmetry, causing high-Q modes to be generated when incident light passes through the structure. The operating wavelength of this mode is determined by the cell period P. In this embodiment, the cell period P of the 196 metasurface units 3 varies in 1nm steps within the range of 491-686nm, corresponding to 196 high-Q modes with different operating wavelengths. These 196 different operating wavelengths cover the wavelength range of 780-1040nm, ensuring that the high-resolution, high-throughput near-infrared on-chip spectrometer of the dielectric metasurface encoder 1 is used for near-infrared detection.

[0034] The most typical characteristic of high-Q mode is that it produces a narrow-band response, and the linewidth of the narrow band is inversely proportional to the Q factor. A high Q factor results in a narrow linewidth for the narrow-band response, ensuring that the high-resolution, high-throughput near-infrared on-chip spectrometer based on dielectric metasurface encoder 1 has high spectral resolution.

[0035] The high-Q mode absorbs only light corresponding to the operating wavelength, while light of all other wavelengths passes through the diatomic structure of cell 5 without obstruction. In this embodiment, the dielectric metasurface encoder 1 uses this principle to encode the incident light. This mode is different from the mode of most on-chip spectrometers that "only allows a single wavelength to pass through". This mode can maximize the extraction efficiency of light energy and ensure that the high-resolution, high-throughput near-infrared on-chip spectrometer of the dielectric metasurface encoder 1 has high light throughput.

[0036] The diatomic structure retains its C4v symmetry, making it independent of the polarization state of the incident light and eliminating the need for an additional polarizer. This not only simplifies the overall structure and reduces the size of the high-resolution, high-throughput near-infrared on-chip spectrometer of the dielectric metasurface encoder 1, but also avoids the light energy loss caused by the polarizer, further improving the light throughput of the high-resolution, high-throughput near-infrared on-chip spectrometer of the dielectric metasurface encoder 1.

[0037] The encoding process of dielectric metasurface encoder 1 uses Gaussian functions. The concept of linear combination, specifically: incident light The dielectric metasurface encoder 1 uses its 196 metasurface units 3 to encode 196 coded spectral response values, respectively. .

[0038] Its mathematical expression is: (1) in, The spectral response value corresponding to the metasurface unit 3 is measured for the CMOS image sensor 2; Measurement curves of the metasurface unit 3 The corresponding measurement vector, ; Let be the incident spectral vector. ; This represents the total number of spectral samples. In this embodiment, the total number of metasurface units 3 is 3. ; .

[0039] The measurement curves of metasurface units 3 were obtained through calibration. The 196 metasurface units 3 correspond to 196 different measurement curves, some of which are shown below. Figure 3 As shown, Figure 4 The Q factor and luminous flux of the measurement curve are shown in the figure. It can be seen from the figure that the average Q factor of the measurement curve reaches 608.42 and the average luminous flux reaches 0.687. The results show that the present invention has high luminous flux and can perform weak light detection.

[0040] The CMOS image sensor 2 is used to receive spectral information encoded by the dielectric metasurface encoder 1. The dielectric metasurface encoder 1 uses a SiO2 substrate 9, which is fully compatible with the process of the CMOS image sensor 2. It can be directly integrated onto the surface of the CMOS image sensor 2 to form a system-on-a-chip without the need for complex optical components, thus meeting the chip-level integration requirements. It can be used in scenarios such as drones, satellites, and portable inspection equipment.

[0041] The signal processing module 4 is used to reconstruct the spectral information of the incident light from the encoded spectral information received by the COMS image sensor 2.

[0042] In this embodiment, the signal processing module 4 uses a piecewise polynomial to discretize the spectral information received by the CMOS image sensor, and constructs an algorithm model to solve it by using the least squares method, combined with TV regularization constraints, and applying non-negativity constraints.

[0043] Its mathematical expression is: (2) in, The measurement matrix of the dielectric metasurface encoder 1 obtained for calibration, ; The photocurrent vector measured by CMOS image sensor 2. ; It is a second-order difference matrix; is the regularization coefficient. TV regularization is used to transform ill-posed problems into well-posed problems. At the same time, it adopts piecewise smoothing, noise reduction and edge preservation to avoid over-smoothing and ensure the existence, uniqueness and stability of the reconstruction results. In this embodiment, second-order TV regularization is used to reduce the step effect and make the reconstructed spectrum smoother and more accurate.

[0044] Figure 5A comparison graph is shown between the bimodal spectral measurement results (peak spacing 0.7 nm) obtained using the high-resolution, high-throughput near-infrared on-chip spectrometer based on dielectric metasurface encoding of the present invention and the bimodal spectral measurement results obtained using a commercial spectrometer. The definitions of the quantification indicators Pearson correlation coefficient (PCC) and root mean square error (RMSE) in the graph are as follows: (3) (4) In the formula, , These represent the first two peaks of the bimodal spectral measurement results from the commercial spectrometer. Individual data and average; , The first two terms represent the bimodal spectral measurement results obtained by the high-resolution, high-throughput near-infrared on-chip spectrometer based on the dielectric metasurface encoder 1 of this invention. The data and average values ​​are used. PCC measures the degree of linear correlation, and RMSE reflects the average error magnitude. PCC measures the degree of linear correlation. The quantitative indicators show that PCC=0.9954, which is very close to 1, indicates that the measurement results are very similar. RMSE=0.0067 indicates that the error is very small. The results show that the present invention achieves high-resolution near-infrared spectroscopy measurement.

[0045] Figure 6 The figure shows a comparison between the broadband spectral measurement results obtained by the high-resolution, high-throughput near-infrared on-chip spectrometer based on the dielectric metasurface encoder 1 of this invention and the broadband measurement results of a commercial spectrometer. As can be seen from the figure, the result curve of this invention closely matches the result curve of the commercial spectrometer. The quantitative indicators show that PCC=0.9999, which is very close to 1, indicating that the measurement results are very similar, and RMSE=0.0029, indicating that the error is very small. Both visual observation and quantitative indicators show that this invention achieves high-precision near-infrared spectral measurement.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1), characterized in that, It includes a dielectric metasurface encoder (1) for encoding the spectral information of incident light; COMS image sensor (2) is used to receive spectral information encoded by the dielectric metasurface encoder (1); The signal processing module (4) is used to solve the inverse problem corresponding to the encoding of the dielectric metasurface encoder (1) to reconstruct the spectral information of the incident light.

2. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 1, characterized in that, The dielectric metasurface encoder (1) is composed of several metasurface units (3).

3. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 2, characterized in that, The metasurface unit (3) is a TiO2 thin film (8) etched with an array of first square nanopores (6) and second square nanopores (7). The array of first square nanopores (6) and second square nanopores (7) is arranged in a square lattice. Each lattice is a unit cell (5). Each unit cell (5) is a diatomic structure containing two first square nanopores (6) with side lengths of L1 and second square nanopores (7) with side lengths of L2.

4. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 3, characterized in that, The TiO2 thin film (8) is deposited on the SiO2 substrate (9), and is fully compatible with the process of the COMS image sensor (2). It is directly integrated on the surface of the COMS image sensor (2) to form a system on chip.

5. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 4, characterized in that, The diatomic structure of the unit cell (5) disrupts its translational symmetry, generating a high-Q mode. The diatomic structure of the unit cell (5) retains its C4v symmetry, making the diatomic structure of the unit cell (5) independent of the polarization state of the incident light, thus eliminating the need for an additional polarizer.

6. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 5, characterized in that, The period P of the cell (5) determines the operating wavelength of the high-Q mode.

7. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 6, characterized in that, Several of the metasurface units (3) employ cell (5) with different periods to enable the operating wavelength of the high-Q mode to cover the operating range of the high-resolution, high-throughput near-infrared on-chip spectrometer based on the dielectric metasurface encoder (1).

8. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 5, characterized in that, The high-Q mode has a single-mode coverage of 5 times the wavelength range in the near-infrared band compared to the visible light band, making it suitable for near-infrared spectral detection.

9. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 5, characterized in that, The high-Q mode has a narrow-band response with a linewidth of 2 nm in the near-infrared band, ensuring high spectral resolution.

10. A high-resolution, high-throughput near-infrared on-chip spectrometer based on a dielectric metasurface encoder (1) according to claim 5, characterized in that, The high-Q mode only blocks incident light of a specific wavelength and transmits incident light of all other wavelengths, maximizing the extraction efficiency of light energy and ensuring high light flux.

Images