Calculation reconstruction spectrum detection device and method based on metal particle scattering

Abstract

The invention discloses a calculation reconstruction spectrum detection device and method based on metal particle scattering. The device comprises an input system, a multi-mode waveguide, metal particles and a two-dimensional photoelectric detector, the input system is a single-mode waveguide, light is injected into the multi-mode waveguide after being stably transmitted in the input system, and the metal particles are randomly distributed on the upper surface of the multi-mode waveguide and can scatter and output the transmitted light in the multi-mode waveguide from the upper surface. Therefore, the incident light spectrum is detected by the two-dimensional photoelectric detector placed above the multimode waveguide, and high-precision and high-resolution reconstruction of the incident light spectrum can be realized. Compared with an existing defect scattering mode, metal nanoparticle scattering has more sensitive wavelength response, so that the method has better performance; in addition, processing of the device is more convenient than that of a defect scattering type device. Compared with a traditional commercial spectrograph, the device has the advantages of being few in device, compact in structure and small in size, the system complexity and cost of the spectrograph are effectively reduced, and the portability of the spectrograph is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of spectrometers, and in particular to a device and method for calculating and reconstructing a spectrum based on metal particle scattering. Background Art

[0002] Spectrometers play a vital role in many applications, such as astronomical detection, biological and chemical characterization, and material analysis. At present, integrated photon spectrometers based on the principles, technologies, and devices of integrated photonics have attracted widespread attention due to their small size, light weight, low energy consumption, and low cost. Although integrated photon spectrometers based on on-chip dispersion mechanisms, such as arrayed waveguide gratings (AWGs) and on-chip step grating spectrometers, are smaller in size than traditional spectrometers, their spectral detection principles are similar to those of traditional spectrometers. To obtain higher spectral resolution, the size will also increase accordingly, which is still challenging for extremely compact application scenarios, such as integrated spectral detection devices in bracelets or mobile phones.

[0003] In recent years, a computational reconstruction type integrated photonic spectrometer has come into view, which can combine algorithms to overcome size limitations. Its working principle includes using a device or structure with a spectral response to establish a mapping relationship between the spectrum and the detected signal. This relationship is stored in a transfer matrix. By obtaining the transfer matrix through pre-calibration, the input spectrum can be reconstructed from the detected signal. Structures with wavelength-dependent properties, such as quantum dots, disordered scattering media, photonic crystal-based filter arrays, and even single nanowires, have been proposed and verified for reconstructing spectra. At present, reconstruction-type integrated photonic spectrometers have excellent potential in application scenarios with extreme miniaturization requirements.

[0004] The current computationally reconstructed integrated photon spectrometers have a more common problem, that is, the number of effective sampling channels is strictly limited, which greatly affects the performance of this type of instrument, resulting in key parameters such as spectral resolution, accuracy, and spectral detection range generally being much lower than those of integrated photon spectrometers based on on-chip dispersion mechanisms and traditional spectrometers. The invention patent "A defect scattering computationally reconstructed spectral detection device and method" (patent application number: CN202310113989.6) can achieve tens of thousands or even more effective detection channels in an extremely small size, greatly improving the parameter performance of spectral detection. However, it is difficult to artificially create random defects in multimode waveguides. In addition, the wavelength response sensitivity of such defects is limited, and scatterers with more sensitive wavelength response are needed to improve detection performance. Summary of the invention

[0005] The present invention proposes a computationally reconstructed spectrum detection device and method based on metal particle scattering. The present invention utilizes the metal particle scattering structure and detects the two-dimensional scattered light field to obtain different spectral responses, and utilizes spectral reconstruction to obtain the target spectrum. The reconstructed spectrum has high resolution and high speed, and does not use grating prism filters and other spectral elements. It has few devices, compact spatial optical path, and small size, thereby solving the defects of traditional spectrometers that have high precision requirements for optical components, large size, expensive and inconvenient to carry, greatly increasing spectral sampling, and obtaining high-precision spectra with a small structure.

[0006] The technical solution adopted by the present invention is:

[0007] A computationally reconstructed spectrum detection device based on metal particle scattering includes an input system, a multimode waveguide, metal particles, and a two-dimensional photodetector. The input system is a single-mode waveguide, in which light is injected into the multimode waveguide after stable transmission. The multimode waveguide is connected to the input system. The single-mode waveguide and the multimode waveguide use transparent materials or low-absorption materials in the working band. The metal particles are distributed on the upper surface of the multimode waveguide. When light passes through the multimode waveguide, it is scattered and output from the upper surface by the metal particles distributed on the upper surface, and is detected by the two-dimensional photodetector placed above the multimode waveguide. The light field distribution in the multimode waveguide varies with wavelength. The metal particles use metal materials with wavelength response, which have different light scattering efficiencies at different wavelengths. Therefore, the light field intensity distribution detected by the two-dimensional photodetector has a high-sensitivity spectral response.

[0008] Furthermore, the input system is structured so that the light is stable after propagation, so that the spot and power of the input light remain stable; the width of the single-mode waveguide satisfies that the light propagation is single-mode in the working band of the spectrometer, the thickness of the single-mode waveguide is the same as the width, and the length of the single-mode waveguide ensures that the light is stably propagated in single mode during the propagation process.

[0009] Furthermore, the transparent material is silicon nitride, silicon, silicon dioxide, lithium niobate, III-V semiconductor compounds or polymer materials or other materials that can be used to make optical waveguides.

[0010] Furthermore, the metal material used is Au, Pt, Al, Cu, Cr, Ni or other metal particles having different characteristics of light scattering efficiency at different wavelengths.

[0011] Furthermore, the metal particles are in any shape that can achieve scattering of light from the optical waveguide, and the three-dimensional shape is manifested as protrusions upward from the waveguide surface.

[0012] Furthermore, the metal particles are made of different materials, and their sizes and distributions have random amounts, or one of them has a random amount, or part of the total number has a random amount. The obtained metal particles are randomly distributed on the surface of the optical waveguide, or partially embedded in the waveguide, and the light propagation in the optical waveguide is scattered through the metal particle units.

[0013] Furthermore, the basic array of metal particles is an N×M array, and the random amount refers to a random deviation near the original regular array point position, and the range of this deviation does not exceed the distance between two adjacent metal particles in the basic array.

[0014] Furthermore, the detection method is to detect the upper surface of the waveguide, that is, the two-dimensional light field scattered by the metal particles, to obtain richer spectral information.

[0015] A method for calculating and reconstructing spectrum detection based on metal particle scattering, comprising the following steps:

[0016] 1) Calibration: allowing a number of calibration lights of known wavelengths and intensities within a band to enter the device and scatter from the upper surface of the optical waveguide, the device being the computationally reconstructed spectrum detection device based on metal particle scattering as described in any one of claims 1 to 8, the light interferes at the output end of the waveguide, the two-dimensional photodetector collects the interference light signal of the spatial region output from the optical waveguide, obtains the light field intensity distribution on different pixels of the two-dimensional photodetector, and stores the light field intensity values ​​obtained at this series of different wavelengths in the transmission matrix as a spectral response function;

[0017] 2) Collect the intensity distribution of the side scattered light field: When light of unknown spectrum enters the device, the light interferes from the output end of the optical waveguide to obtain the intensity distribution of the light field on the two-dimensional photodetector;

[0018] 3) Reconstruct spectrum: The calibrated transmission matrix and the light field distribution of the unknown light form a linear equation, and the reconstructed spectrum of the light to be measured is obtained by solving the linear equation.

[0019] The beneficial effects of the present invention are as follows: the present invention obtains signals with different spectral responses through metal particle scattering, and detects the light field on the surface of the waveguide, which greatly reduces the number of waveguides required. Since the optical waveguide is used as the main structure, the volume of the device is small, only a few square millimeters, which can reduce the volume of the spectrometer. The spectral response correlation of the metal particles used is low, so a light field pattern with low correlation can be obtained, which is conducive to calculation and reconstruction. In addition, the entire device has a high degree of integration and correspondingly high stability, which is conducive to subsequent detection. Since the light field distribution in the multimode waveguide and the scattering efficiency of the metal particles have a strong wavelength response, the light intensity distribution detected by the two-dimensional photodetector has a sensitive wavelength response, and the light intensity distribution information can be used to achieve high-precision and high-resolution reconstruction of the incident light spectrum. Compared with the defect scattering method of the prior art, the metal nanoparticle scattering has a more sensitive wavelength response, so the present invention has better performance; in addition, the processing of the device is more convenient than the defect scattering type. The present invention has no specific requirements on the material size and shape of the metal, and only needs to have wavelength response and the ability to scatter light. Therefore, this device has a high tolerance for processing errors and is conducive to processing. It also avoids the defects of traditional spectrometers that have high precision requirements for optical components, large size, expensive and inconvenient to carry. Therefore, compared with traditional commercial spectrometers, the present invention has the advantages of fewer components, compact structure and small size, which effectively reduces the system complexity and cost of the spectrometer and improves the portability of the spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the device of the present invention which does not include a two-dimensional photodetector.

[0021] Figure 2 FIG. 1 is a schematic diagram of a device including a two-dimensional photodetector according to the present invention.

[0022] Figure 3 A schematic diagram of the correlation of the spectrometer provided by an embodiment of the present invention over the entire waveband.

[0023] Figure 4 The wavelength responses of metals of different sizes and materials provided in the embodiments of the present invention.

[0024] Figure 5 A schematic diagram of correlation provided by an embodiment of the present invention.

[0025] Figure 6 It is a schematic diagram of a broadband equally spaced spectrum and an incident spectrum reconstructed and restored according to an embodiment of the present invention.

[0026] In the figure, 1. Input system, 2. Multimode waveguide, 3. Metal particles, 4. Two-dimensional photodetector. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below through specific embodiments:

[0028] The present invention is not limited to the following specific embodiments. It should be understood that the following specific embodiments are only exemplary illustrations and explanations of the present invention and do not limit the protection scope of the present invention. Any simple changes or modifications made by adopting the design structure and concept of the present invention will fall within the protection scope of the present invention.

[0029] A computationally reconstructed spectrum detection device based on metal particle scattering comprises an input system, a multimode waveguide, metal particles and a two-dimensional photoelectric detector.

[0030] Preferably, the input system is a single-mode waveguide, the width of the single-mode waveguide satisfies that light propagation is single-mode in the working band of the spectrometer, the thickness of the single-mode waveguide is the same as the width, and the length of the single-mode waveguide can ensure that the light propagates stably in single-mode during propagation, thereby maintaining the stability of the input light field.

[0031] Preferably, the material of the single-mode waveguide is a transparent material or a low-absorption material in the working band. The single-mode waveguide material is selected as silicon nitride in the present invention, but is not limited to silicon, silicon dioxide, lithium niobate, III-V semiconductor compounds or polymer materials.

[0032] Preferably, the metal particle material is a metal with wavelength response, and metal particles such as Au, Pt, Al, Cu, Cr, Ni, etc. are used, which have different characteristics of light scattering efficiency at different wavelengths.

[0033] Preferably, the radius of the metal particles is a random value, the basic array of the metal particles is an N×M array, the array is laid flat on the entire upper surface of the multimode waveguide, and the position of each basic unit in the length and width directions of the multimode waveguide also has a random amount, and the random amount refers to a random deviation near the original regular array point position, and the range of this deviation does not exceed the distance between two adjacent metal particles in the basic array. The spherical centers of the metal particles are all on the surface of the multimode waveguide, and the metal particles appear as hemispherical protrusions on the waveguide surface. Light is scattered from the upper surface of the waveguide through the metal particles.

[0034] Preferably, the photodetector is a two-dimensional detector to fully sample the two-dimensional light field scattered from the upper surface of the waveguide by the metal particles.

[0035] A method for calculating and reconstructing spectrum detection based on metal particle scattering, the steps of which include:

[0036] 1) Calibration: Allow a number of calibration lights of known wavelength and intensity within the band to enter the device, scatter on the surface of the optical waveguide, and obtain the intensity distribution of its light field pattern through a two-dimensional photodetector. The intensity values ​​obtained at this series of different wavelengths are stored in the transmission matrix as a spectral response function;

[0037] 2) Collect the intensity distribution of the light field scattered from the upper surface of the waveguide: When light of unknown spectrum enters the device, the light is scattered from the upper surface of the optical waveguide, and the intensity distribution of the light field on the two-dimensional photodetector is obtained;

[0038] 3) Reconstruct spectrum: The calibrated transmission matrix and the light field distribution of the unknown light form a linear equation, and the reconstructed spectrum of the light to be measured is obtained by solving the linear equation.

[0039] Preferably, the two-dimensional photodetector collects light signals scattered from the upper surface of the optical waveguide.

[0040] Preferably, the equation used in the spectrum reconstruction process is as follows:

[0041]

[0042] In the above formula:

[0043] : Spectral component matrix of input light;

[0044] : The transmission matrix of the device, the spectral response matrix of the device to be calibrated;

[0045] : The light field intensity distribution matrix obtained on the detector.

[0046] Expanding this equation yields:

[0047]

[0048] Preferably, the detailed steps of the spectrum reconstruction process are as follows:

[0049] 1. Calibrate to obtain the transmittance function Tn at different positions of the device. Tn is the transmittance function of the nth spatial spot channel. The wavelength S of the incident light is continuously adjusted to obtain m equal-wavelength interval sampling Tn. These Tn constitute the transmission matrix T(n,m) of the device, which describes the spectral response of the device. T(n,m) is a two-dimensional matrix:

[0050]

[0051] 2. Measure the device response of the light to be measured. Introduce the unknown light into the single-mode waveguide. After propagating to the multi-mode optical waveguide area, the light will be scattered from the upper surface of the waveguide through the metal particles to form a light spot. The intensity In of the light spot can be obtained on the two-dimensional photodetector. In is the light field intensity at the nth pixel point on the two-dimensional photodetector, corresponding to the nth spatial spectrum channel. The light field intensity distribution I is a one-dimensional matrix with a length of n:

[0052]

[0053] 3. Solve the unknown spectrum. The unknown spectrum S is solved by solving the linear equation system Obtain. S is a one-dimensional matrix of length m:

[0054]

[0055] Preferably, m≥n.

[0056] like Figure 1 , showing the specific structure of a specific embodiment of the present invention. The metal particle scattering calculation and reconstruction spectrum detection device of the present invention is mainly composed of an input system 1, a multimode waveguide 2, metal particles 3, and a two-dimensional photoelectric detector 4.

[0057] When in use, the input system uses a single-mode waveguide, and couples the incident light through a pair of optical fiber lenses. The incident light is stabilized as single-mode light after propagating through the single-mode waveguide, and then enters the multi-mode waveguide 2, and through the metal particles 3 on the multi-mode waveguide, the energy in the multi-mode waveguide is scattered out, and the light field pattern is collected by the two-dimensional photodetector 4. After the device is calibrated, the light spot generated by the unknown light can be used to obtain the spectrum of the unknown light through the reconstruction algorithm.

[0058] In a specific embodiment, the materials of the input system and the multimode waveguide are both selected to be silicon nitride. In addition to silicon nitride, any material that remains transparent in the working band of the instrument can be used. For example, if used near the infrared band, the material of the waveguide can also be silicon. The cross-sectional dimensions of the input system are 1μm×1μm, and the length of the waveguide is 200 μm. This is to maintain the stability of the input light in the working band of the device. The working band of the device is 1-1.5 μm. Within the working band, the input system can make all wavelengths of input light be coupled into the single-mode waveguide and then converted into single mode after propagation, and maintain the stability of an input light spot during splitting, thereby achieving the stability of splitting.

[0059] The cross-sectional size of the multimode waveguide is 0.4 μm×8 μm, the length of the waveguide is 4500 μm, and light is transmitted in the multimode waveguide after being introduced from the input system.

[0060] like Figure 2As shown, the metal particle structure, the basic unit of the metal particle is spherical, but not limited to spherical, and can be hexagonal, pentagonal, quadrilateral, cross, triangle, etc., preferably spherical, the metal particle appears spherical on a three-dimensional scale.

[0061] like Figure 3 and Figure 4 As shown, different metal particles will reflect different spectral responses, and the light field correlation is low, increasing the spectral sensitivity of the entire structure.

[0062] The waveguide is made by plasma enhanced chemical vapor deposition (PECVD). The metal particles can be grown directly on the core layer in clusters or metal clusters can be purchased, and then powders are placed in a solution, and then spin-coated on the surface of the structure and dried, or random defects are etched first, and then metal particles are deposited. In the specific embodiment, spin coating and drying are used.

[0063] The spectrum reconstruction comprises the following steps:

[0064] In a specific embodiment, a continuously adjustable light source is used to calibrate the device, and the equation used during calibration is as follows:

[0065]

[0066] In the above formula:

[0067] : Spectral component matrix of input light;

[0068] : The transmission matrix of the device, the spectral response matrix of the device to be calibrated;

[0069] : The spot intensity matrix obtained on the detector.

[0070] Expanding this equation yields:

[0071]

[0072] During calibration, input monochromatic light of known wavelength and intensity The corresponding light intensity distribution can be obtained on the two-dimensional photodetector , these two known values ​​can be used to calibrate The components in the transmission matrix are used to obtain the entire transmission matrix of the device by inputting monochromatic light with equally spaced wavelengths within the working band of the device. m is the number of spectral components, n is the number of pixels used in the calculation of the two-dimensional photodetector, m ≥ n.

[0073] Finish After the transfer matrix is ​​calibrated, the unknown spectrum is input again. , the spot intensity distribution function is obtained on the two-dimensional photodetector through the metal scattering on the upper surface of the device , by solving the equation , the components of the unknown spectrum can be obtained. Figure 5 This figure shows the correlation of the wavelength interval of the spectrometer in the 1-1.5 μm band. The half-width δλ at half-peak represents its theoretical resolution of 0.1 nm. Figure 6 As shown, a single peak reconstruction result of 1-1.5 μm can be obtained in the entire working band.

[0074] In summary, the present invention provides a computationally reconstructed spectral detection device and method based on metal particle scattering. The device includes an input system, a multimode waveguide, metal particles, and a two-dimensional photodetector. The technical solution of the present invention utilizes the different scattering efficiencies of input light of different wavelengths passing through metal particles on a multimode waveguide to obtain a light field pattern with high wavelength sensitivity on a two-dimensional detector to reconstruct the incident light spectrum, and has high spectral resolution and reconstruction accuracy. Compared with traditional commercial spectrometers, it has the advantages of fewer components, compact structure, and small size, which effectively reduces the system complexity and cost of the spectrometer and improves the portability of the spectrometer.

[0075] The above embodiment is only one example to fully illustrate the principle and spirit of the present invention. Those skilled in the art can make various changes and modifications to the described method. The technical scope of the present invention is not limited to the contents of the specification, and the protection scope of the present invention is subject to the claims.

Claims

1. A computationally reconstructed spectrum detection device based on metal particle scattering, characterized in that: The invention comprises an input system, a multimode waveguide, metal particles, and a two-dimensional photoelectric detector. The input system is a single-mode waveguide, in which light is injected into the multimode waveguide after stable transmission. The single-mode waveguide and the multimode waveguide use transparent materials or low-absorption materials in the working band. The metal particles are distributed on the upper surface of the multimode waveguide. When light passes through the multimode waveguide, it is scattered and output from the upper surface by the metal particles distributed on the upper surface, and detected by the two-dimensional photoelectric detector placed above the multimode waveguide. The light field distribution in the multimode waveguide varies with the wavelength. The metal particles use metal materials with wavelength response, which have the characteristics of different light scattering efficiencies at different wavelengths.

2. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 1, characterized in that: The input system is structured so that the light is stable after propagation, so that the spot and power of the input light remain stable; the width of the single-mode waveguide satisfies that the light propagation is single-mode in the working band of the spectrometer, the thickness of the single-mode waveguide is the same as the width, and the length of the single-mode waveguide ensures that the light is stably propagated in single mode during the propagation process.

3. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 1, characterized in that: The transparent material or low absorption material is silicon nitride, silicon, silicon dioxide, lithium niobate, III-V semiconductor compounds or polymer materials or other materials that can be used to make optical waveguides.

4. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 1, characterized in that: The metal material used is Au, Pt, Al, Cu, Cr, Ni or other metal particles having different characteristics of light scattering efficiency at different wavelengths.

5. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 1, characterized in that: The metal particles are in any shape that can scatter light from the optical waveguide, and the three-dimensional shape is shown as a protrusion upward from the waveguide surface.

6. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 1, characterized in that: The metal particles are made of different materials, and their sizes and distributions have random amounts, or one of them has a random amount, or part of the total number has a random amount. The obtained metal particles are randomly distributed on the surface of the optical waveguide, or partially embedded in the waveguide, and the light propagation in the optical waveguide is scattered through the metal particle units.

7. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 6, characterized in that: The basic array of metal particles is an N×M array, and the random amount refers to a random deviation near the original regular array point position, and the range of this deviation does not exceed the distance between two adjacent metal particles in the basic array.

8. The computationally reconstructed spectrum detection device based on metal particle scattering according to claim 1, characterized in that: The detection method is to detect the upper surface of the waveguide, that is, the two-dimensional light field scattered by metal particles, to obtain richer spectral information.

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