A kind of computing reconstruction spectrum detection device and method based on helical waveguide grating

Abstract

The present application relates to a kind of based on helical waveguide grating computing reconstruction spectrum detection device and method, belong to the technical field of spectrometer, including: input waveguide, waveguide grating, curved waveguide, output waveguide and photoelectric detector;Through waveguide grating, efficient scattering of light from the upper surface of waveguide is realized, then two-dimensional photoelectric detector is used to capture interference pattern with high wavelength sensitivity, and then the incident spectrum is accurately reconstructed, the beneficial effects of the present application are as follows: compared with the existing spectrometer, the device has the advantages of high device integration, compact waveguide arrangement and small size, simplifies the system structure of spectrometer, reduces manufacturing cost, and greatly improves the portability of equipment;At the same time, the device uses computing reconstruction method for spectrum reconstruction, can accurately reproduce incident spectrum, and has excellent spectral resolution, improves the spectral detection in various scenes.

Description

Technical Field

[0001] This invention belongs to the field of spectrometer technology, and specifically relates to a computational reconstruction spectral detection device and method based on a helical waveguide grating. Background Technology

[0002] Spectrometers play an indispensable and crucial role in numerous fields, including astronomical detection, biochemical characterization, and materials analysis. In recent years, with the continuous increase in demands for portability and low power consumption, small-sized, lightweight, and low-power spectrometers have attracted much attention, leading to rapid technological advancements. Currently, two main categories of small-sized spectrometers have emerged: one based on on-chip dispersion principles, typically represented by arrayed waveguide grating (AWG) spectrometers and on-chip echelle grating spectrometers; the other based on on-chip Fourier transform principles, such as standing-wave integrated Fourier transform spectrometers. Although these two types of spectrometers have achieved relatively compact sizes, they essentially still retain the core working logic of traditional spectrometers, exhibiting inherent limitations. To pursue higher spectral resolution, the device size must be increased accordingly, and the core bottleneck of "size and resolution mutually constraining each other" remains unbroken, severely limiting the design and application of ultra-compact spectrometers.

[0003] To address this challenge, a novel type of "reconstruction spectrometer" has emerged in recent years. Integrating algorithmic advantages, it aims to overcome traditional limitations in resolution and size. Its core working principle is as follows: Utilizing devices or structures with specific spectral response characteristics, a mapping relationship between the incident spectrum and the detection signal is established and stored in a transfer matrix. After accurately obtaining the transfer matrix through a pre-calibration process, the input spectrum can be reconstructed from the actual detection signal. Currently, various structures with wavelength correlation characteristics have been proposed and verified for spectral reconstruction, such as quantum dots, disordered scattering media, photonic crystal-based filter arrays, and even single nanowires. With its unique potential to achieve high-resolution spectral detection in ultra-compact sizes, reconstruction spectrometers show extremely broad development prospects. Summary of the Invention

[0004] This invention proposes a computational reconstruction spectral detection device and method based on a helical waveguide grating, which addresses the technical problem of poor detection of multiple spectra by optical elements in spectrometers. By utilizing a helical waveguide grating, efficient light scattering and accurate capture of interference light fields are achieved. The target spectrum is quickly reconstructed through a spectral reconstruction algorithm. The reconstruction result has the significant advantages of high resolution and high response speed. It eliminates the discrete spectroscopic elements such as gratings, prisms, and filters required by traditional spectrometers. This invention features high device integration, compact spatial optical path, and small size, thus improving the detection of multiple spectra.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A computational reconstruction spectral detection device based on a helical waveguide grating includes: an input waveguide, a waveguide grating, a bent waveguide, an output waveguide, and a photodetector.

[0007] Optionally, the input waveguide is a single-mode waveguide. The width of the input waveguide is optimized to match the working band of the spectrometer to ensure that the light propagates in single-mode form throughout the band. The thickness of the single-mode waveguide is consistent with its width, and the length is designed to ensure that the light maintains single-mode characteristics stably during propagation, thereby effectively ensuring the stability of the input light field and providing a reliable light field basis for subsequent spectral detection and reconstruction.

[0008] Optionally, the material of the single-mode waveguide is a low-absorption material in the operating band. The single-mode waveguide material is selected as silicon dioxide, but is not limited to one of silicon, silicon nitride, lithium niobate, group III-V semiconductor compounds or polymer materials.

[0009] Optionally, the bent waveguide has low bending loss. The material of the bend is the same as that of the single-mode waveguide. The material of the bent waveguide is silicon dioxide. The material of the bent waveguide is a material that is in the operating band. Silicon dioxide is used, but it is not limited to one of the following materials: silicon, silicon nitride, lithium niobate, group III-V semiconductor compounds or polymer materials.

[0010] Optionally, the spiral waveguide grating has different etching directions, specifically towards the center of the waveguide. The material of the spiral waveguide grating is the same as that of the single-mode waveguide, and the waveguide grating material is silicon dioxide. The material of the waveguide grating is a material used in the operating wavelength range, and silicon dioxide is used, but it is not limited to using one of the following materials: silicon, silicon nitride, lithium niobate, group III-V semiconductor compounds, or polymer materials.

[0011] Furthermore, the spiral waveguide grating has different etching angles and etching depths to match waveguides with different parameters, including waveguide length, waveguide material, waveguide width, and waveguide thickness.

[0012] Furthermore, the output waveguide is a single-mode design with the same parameters as the input waveguide, used for optical field matching transmission and detection of the remaining optical field within the entire waveguide.

[0013] Furthermore, the photodetector is a two-dimensional detector used to capture a two-dimensional light field on the upper surface of the waveguide.

[0014] A computational reconstruction spectral detection method based on a helical waveguide grating includes the following steps:

[0015] Calibration: Several known wavelengths and intensities of calibration light within the band range are introduced into the device, interfered on the upper surface of the optical waveguide and output. The field intensity distribution or interference pattern intensity distribution on different pixels is obtained through a photodetector. The light field intensity values ​​obtained at different wavelengths are stored in the transmission matrix as a spectral response function.

[0016] Acquiring the optical field interference intensity distribution on the upper surface of the waveguide: When light of an unknown spectrum enters the device, the light is output from the upper surface of the optical waveguide and interferes, thus obtaining the optical field intensity distribution on the photodetector;

[0017] Spectrum reconstruction: The calibrated transfer matrix and the light field distribution of the unknown light are combined to form a linear equation, and the reconstructed spectrum of the light under test is obtained by solving the linear equation.

[0018] The photodetector collects the optical signal that is output from and interferes with the upper surface of the entire optical waveguide.

[0019] Furthermore, spectral reconstruction includes the following steps:

[0020] The device was calibrated using a continuously adjustable light source, and the equations used during calibration were as follows:

[0021] ;

[0022] in, The spectral composition matrix of the input light; For the device's transmission matrix; To obtain the intensity matrix of the interference spot on the detector; This indicates that for all incident light wavelengths The integral of represents the device’s total response to incident light across the full spectrum.

[0023] Expanding the equations used in calibration yields the linear calibration equations for the device response under multiple light sources:

[0024] ;

[0025] in, To obtain the transmittance function at different locations of the calibration device, representing the first... The spectral component affects the first The linear contribution coefficient of the number of pixels reflects the coupling strength between the light source and the channel; For the first The intensity of each spectral component The number of spectral components; For the first The response value or spot response intensity of a number of pixels The number of pixels or points used in the calculation of the photodetector.

[0026] Specifically, the transmittance function at different locations of the calibration device is obtained. , For the first The transmittance function of each spatial light spot channel is used to continuously adjust the wavelength of the incident light. ,get Sampled at equal wavelength intervals , Transmission matrix of the components This describes the spectral response of the device. For a two-dimensional matrix:

[0027] ;

[0028] Measuring the device response to the light under test involves introducing the unknown light into a single-mode waveguide. After propagating to a random waveguide region, the light is output and interferes at the output end, forming a light spot. The intensity of this light spot can then be obtained on a photodetector. , For the first photodetector The light spot or light field intensity at the nth pixel represents the light spot or light field intensity at the nth pixel. Spectral channels in space, light field intensity distribution It is a length of One-dimensional matrix:

[0029] ;

[0030] Solving for an unknown spectrum involves determining the intensity of its unknown spectral components. By solving the system of linear equations get, For length is One-dimensional matrix:

[0031] ;

[0032] in, ≥ .

[0033] The beneficial effects of this invention are:

[0034] The computational reconstruction spectral detection device based on a spiral waveguide grating of this invention acquires scattered signals through the spiral waveguide grating and detects the interference light field on the upper surface of the waveguide during use. The spiral waveguide design significantly reduces the space required for waveguide arrangement. At the same time, with the optical waveguide as the core structural carrier, the device volume can be controlled to the order of a few square millimeters, which significantly reduces the overall size of the spectrometer.

[0035] The tightly and regularly arranged waveguides of the helical waveguide gratings enable synergistic effects between scattered light fields, resulting in interference patterns with low wavelength correlation. This provides a high-quality data foundation for subsequent computational reconstruction, effectively improving reconstruction accuracy and efficiency. Furthermore, the device exhibits high integration and excellent structural stability, ensuring reliable precision in subsequent detection. Notably, the etching angle, direction, and depth of each helical waveguide grating can be flexibly customized according to specific application scenarios, demonstrating strong versatility and adaptability to various spectral detection needs. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the spectral detection device of the present invention.

[0038] Figure 2 This is a schematic diagram of waveguide grating structures with different etching directions according to the present invention.

[0039] Figure 3 This is a schematic diagram of the detection method of the spectrometer of the present invention.

[0040] Figure 4 This is a schematic diagram of the two-dimensional light field on the photodetector of the present invention.

[0041] Icons: 1. Input waveguide; 2. Bent waveguide; 3. Waveguide grating; 4. Output waveguide; 5. Photodetector. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0043] This invention is not limited to the following specific embodiments. It should be understood that the following specific embodiments are only illustrative and explanatory of this invention and do not limit the scope of protection of this invention. Any simple changes or modifications made to the design structure and ideas of this invention fall within the scope of protection of this invention.

[0044] Example 1

[0045] like Figure 1As shown, this embodiment provides a computational reconstruction spectral detection device based on a helical waveguide grating. Specifically, it is a detection device that reconstructs the spectrum using a defect scattering calculation method, including: an input waveguide 1, a bent waveguide 2, a waveguide grating 3, an output waveguide 4, and a photodetector 5.

[0046] In use, the input waveguide 1 is a single-mode waveguide, and the incident light is coupled through a fiber optic lens pair. The coupled incident light is stabilized into single-mode light after propagating through the input waveguide 1 of the single-mode waveguide. The bent waveguide 2 is connected to the input waveguide 1 and the output waveguide 4. The bent waveguide 2 is connected to the waveguide grating 3. Adjacent waveguide gratings 3 are also connected through the bent waveguide 2. The output waveguide 4 realizes energy output. The photodetector 5 is located above the entire waveguide structure. The photodetector 5 can realize the capture of two-dimensional interference light field patterns.

[0047] Specifically, the coupled incident light passes through the input waveguide 1 of the single-mode waveguide, then enters the bent waveguide 2, which is a low-bending-loss waveguide, and then enters the waveguide grating 3. 3a, 3b, 3c, and 3d represent different etching directions of the waveguide grating 3, achieving energy scattering towards the upward surface and generating a spectral response signal with low interference correlation. Interference then occurs, and the interference pattern is collected by the photodetector 5. Finally, the incident light outputs its optical energy from the output waveguide 4. After device calibration, the interference pattern can be used to obtain the spectral reconstruction of the unknown light by using the light spot generated by the unknown light and combining it with a reconstruction algorithm.

[0048] In a specific embodiment, the input waveguide 1, the bent waveguide 2, the helical waveguide grating 3, and the output waveguide 4 are all made of silicon dioxide. However, any material that remains transparent within the instrument's operating wavelength range can be used, except for silicon dioxide. For example, if used near the infrared band, the waveguide material can also be silicon. The input waveguide 1 has a cross-sectional dimension of 5μm × 5μm and a length of 100μm to ensure the stability of the input light within the device's operating wavelength range of 1.5-1.6μm. Within this range, the input waveguide 1 allows all wavelengths of input light to be coupled and then propagated into a single mode after entering the single-mode waveguide 1, maintaining the stability of a single input light spot during beam splitting, thereby achieving beam splitting stability.

[0049] The curved waveguide 2 has a cross-sectional size of 5μm×5μm and a bending radius of 5μm, enabling low-loss transmission.

[0050] The waveguide grating 3 has a cross-sectional dimension of 5μm × 5μm, a total waveguide length of 5000μm, and the waveguide etching direction is towards the center of the structure, with an etching depth of 2μm and an etching angle of 45°. Light is stably input from the front end, passes through the scattering field of the grating region, and forms a two-dimensional interference light field on it.

[0051] like Figure 2 As shown, the etching direction of waveguide grating 3 is different, and the etching depth and etching angle are different. Modulate to obtain an overall spiral waveguide grating with low interference correlation 3.

[0052] like Figure 3 As shown, photodetector 5 is located on the entire upper surface of the waveguide to achieve two-dimensional sampling of the interference light field.

[0053] like Figure 4 As shown, the two-dimensional light field distribution detected on photodetector 5 can be used to reconstruct the spectrum using the light field pattern.

[0054] The entire waveguide was fabricated using plasma-enhanced chemical vapor deposition (PECVD), while the waveguide grating 3 was formed using reactive ion etching (RIE). A mixture of SF6, N2, and O2 was used as the reactive gas source for the etching process. Under the dry etching mechanism, active free radical molecules and atoms react chemically with the waveguide material, generating volatile products that detach from the substrate, achieving precise material removal. This process can efficiently fabricate helical waveguide grating structures that meet design requirements, with high etching precision and strong morphology controllability.

[0055] Example 2

[0056] Based on Example 1, this example provides a computational reconstruction spectral detection method based on a helical waveguide grating, comprising the following steps:

[0057] Calibration: Several known wavelengths and intensities of calibration light within the band range are introduced into the device, interfered on the upper surface of the optical waveguide and output. The field intensity distribution or interference pattern intensity distribution on different pixels is obtained through photodetector 5. The light field intensity values ​​obtained at different wavelengths are stored in the transmission matrix as a spectral response function.

[0058] Acquire the optical field interference intensity distribution on the upper surface of the waveguide: When light of unknown spectrum enters the device, the light is output from the upper surface of the optical waveguide and interferes, thus obtaining the optical field intensity distribution on the photodetector 5;

[0059] Spectrum reconstruction: The calibrated transfer matrix and the light field distribution of the unknown light are combined to form a linear equation, and the reconstructed spectrum of the light under test is obtained by solving the linear equation.

[0060] Preferably, the photodetector 5 collects an optical signal that is output from the upper surface of the optical waveguide and has interference.

[0061] Spectral reconstruction includes the following steps:

[0062] In a specific embodiment, a continuously adjustable light source is used to calibrate the device, and the equations used during calibration are as follows:

[0063] ;

[0064] in, The input light spectral composition matrix represents the spectral power distribution of the incident light source, indicating the light power per unit wavelength, i.e., the light source at different wavelengths. Energy distribution below; Let be the transfer matrix of the device, represent the spectral response matrix of the device to be calibrated, and represent the device's position. The spectral response function (SRF) at a wavelength of is the device's response to wavelengths of . The light response efficiency, i.e., unit response or unit power; To obtain the intensity matrix of the interference spot on the detector, which is the spatial position of the device. The response output signal at (which could be pixel coordinates or the position of photodetector 5) is, for example, electrical signal strength, gray value, or photocurrent. This indicates that for all incident light wavelengths The integral of represents the device’s total response to incident light across the full spectrum.

[0065] This equation describes the spectral-spatial coupling response process of photodetector 5, which can be understood from two dimensions:

[0066] Spectral dimension: Wavelength integrating devices have different response efficiencies to light of different wavelengths (due to...) The energy distribution of the incident light also differs (determined by...). (Decision), the final output signal It is the integral result of the spectral energy of the light source, weighted by the spectral response function of the device, over the entire wavelength. This is the mathematical expression for how different colors of light will have different responses on the detector when the same optical power is used.

[0067] Spatial dimension: Position-dependent response for imaging devices, such as CCD, CMOS, and focal plane arrays, at different locations. Due to differences in manufacturing processes and optical paths, the spectral response function of each pixel varies. There are differences. Therefore, even the spectral distribution of the incident light... Completely uniform, output signals at different locations They will also differ, which is the root cause of spatial non-uniformity and inconsistent spectral response. After calibration, it can be used... The output signal of the device is corrected to eliminate the effects of spectral response differences and spatial non-uniformity, so as to obtain the true incident light information.

[0068] Expanding the equations used in calibration yields the linear calibration equations for the device response under multiple light sources:

[0069] ;

[0070] in, To obtain the transmittance function at different locations of the calibration device, representing the first... The spectral component affects the first The linear contribution coefficient of the number of pixels reflects the coupling strength between the light source and the channel; For the first The intensity of each spectral component, such as optical power, irradiance, or grayscale value. The number of spectral components; For the first The response value for the number of pixels, i.e., the light spot response intensity, such as the sensor's output current, voltage, pixel grayscale, or detector count. The number of pixels (i.e., the number of points of data) used in calculations for photodetectors, such as multi-pixel sensors and multi-channel detectors. ≥ .

[0071] This equation utilizes the principle of linear superposition, which is essentially a linear superposition of optical signals. It is based on the linear relationship between the spectral components and the pixel number response (i.e., the pixel number works in the linear region, without saturation or nonlinear distortion); the responses of multiple spectral components in terms of pixel number satisfy linear superposition (without nonlinear crosstalk between light sources).

[0072] The spectral composition of the incident light is inferred by using the multi-channel response of the photodetector. The actual output power of each light source is inferred by the array response of the spectral composition and the number of pixels. The non-uniformity and crosstalk of the pixel number response are eliminated by using the inverse of the calibration matrix, and the true spectral composition is restored.

[0073] Specifically, the transmittance function at different locations of the calibration device is obtained. , For the first The transmittance function of each spatial light spot channel is used to continuously adjust the wavelength of the incident light. ,get Sampled at equal wavelength intervals , Transmission matrix of the components This describes the spectral response of the device. For a two-dimensional matrix:

[0074] ;

[0075] Measuring the device response to the light under test involves introducing the unknown light into a single-mode waveguide. After propagating to the random waveguide region, the light is output and interferes at the output end, forming a light spot. The intensity of the light spot can be obtained on the photodetector 5. , For the first photodetector The light spot or light field intensity at the nth pixel represents the light spot or light field intensity at the nth pixel. Spectral channels in space, light field intensity distribution It is a length of One-dimensional matrix:

[0076] ;

[0077] Solving for an unknown spectrum involves determining the intensity of its unknown spectral components. By solving the system of linear equations get, For length is One-dimensional matrix:

[0078] ;

[0079] in, ≥ linear equation system This is the inverse operation of the calibration equation. The intensity of the unknown spectral component. For calibration matrix The inverse matrix, This represents the response value for the number of pixels or the distribution of light field intensity.

[0080] formula Essentially, it is the reverse reconstruction after calibration, and its physical process can be broken down into two steps:

[0081] Forward calibration (completed): Intensity of unknown spectral components Response value of pixel count The calibration matrix is ​​obtained by solving. A linear mapping relationship between the intensity of spectral components and the response of the number of pixels was established.

[0082] Inverse reconstruction (this formula): In practical applications, when the response value of the number of pixels is measured... Then, using the pre-calibrated inverse matrix By deducing the intensity of the unknown spectral components at this time, This enables accurate calculation of spectral composition states.

[0083] The entire spectral reconstruction process involves inputting monochromatic light of known wavelength and intensity during calibration. The corresponding light intensity distribution can be obtained on the photodetector. These two known values ​​can be used to calibrate The components in the transfer matrix are used within the device's operating wavelength range, through the input wavelength. The entire transmission matrix of the device is obtained by using equally spaced monochromatic lights.

[0084] Finish After the transfer matrix is ​​calibrated, for the unknown spectrum input again... The light spot intensity distribution function is obtained by scattering light onto the sensor through the upper surface of the device. By solving the equation It is possible to obtain the components of an unknown spectrum.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A computational reconstruction spectral detection device based on a helical waveguide grating, characterized in that, include: The input waveguide (1) is a single-mode waveguide; A curved waveguide (2) is connected to the input waveguide (1); Waveguide gratings (3) are connected to the curved waveguides (2), and adjacent waveguide gratings (3) are connected to each other through the curved waveguides (2); An output waveguide (4) is connected to a bent waveguide (2), and the output waveguide (4) is used for the output of optical energy; The photodetector (5), located on one side of the waveguide structure, is used to capture two-dimensional interference light field patterns.

2. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 1, characterized in that, The input waveguide (1) is a structure for light propagation and stabilization, used to stabilize the light spot and power of the input light.

3. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 2, characterized in that, The input waveguide (1), the bent waveguide (2), the waveguide grating (3), and the output waveguide (4) are made of materials that are suitable for the operating waveband, and are made of one of the following materials: silicon nitride, silicon, silicon dioxide, lithium niobate, group III-V semiconductor compounds, or polymer materials.

4. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 1, characterized in that, The bent waveguide (2) is a low-loss waveguide, and the bending radius of the bent waveguide (2) satisfies the requirement that the bending loss is small during optical transmission.

5. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 1, characterized in that, The spiral waveguide grating (3) has different scattering directions, which are used to obtain a wavelength-sensitive interference pattern on the upper surface of the waveguide grating (3).

6. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 5, characterized in that, The waveguide grating (3) with its spirals has different etching directions, which in turn gives the waveguide grating (3) different scattering directions.

7. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 6, characterized in that, The waveguide grating (3) of the spiral has different etching angles and etching depths, which are used for different transmission distances and different scattering angles.

8. The computational reconstruction spectral detection device based on a helical waveguide grating according to claim 1, characterized in that, The output waveguide (4) is used to detect the remaining energy in the entire waveguide.

9. A computational reconstruction spectral detection method based on a helical waveguide grating, used to execute the computational reconstruction spectral detection device based on a helical waveguide grating according to any one of claims 1-8, characterized in that, Includes the following steps: Calibration: Several known wavelengths and intensities of calibration light within the band range are introduced into the device, interfered on the upper surface of the optical waveguide and output. The field intensity distribution or interference pattern intensity distribution on different pixels is obtained through a photodetector. The light field intensity values ​​obtained at different wavelengths are stored in the transmission matrix as a spectral response function. Acquiring the optical field interference intensity distribution on the upper surface of the waveguide: When light of an unknown spectrum enters the device, the light is output from the upper surface of the optical waveguide and interferes, thus obtaining the optical field intensity distribution on the photodetector; Spectrum reconstruction: The calibrated transfer matrix and the light field distribution of the unknown light are combined to form a linear equation, and the reconstructed spectrum of the light under test is obtained by solving the linear equation.

10. The computational reconstruction spectral detection method based on a helical waveguide grating according to claim 9, characterized in that, The photodetector collects optical signals that are output from the entire upper surface of the optical waveguide and have interference.

Images