Defect scattering calculation reconstruction spectral detection device and method

Abstract

The application discloses a kind of defect scattering calculation reconstruction spectrum detection device and method, the device includes photoelectric detector, light guide system, optical waveguide, random defect scattering structure, substrate.The defect scattering structure is the recess with random amount of size and position on the surface of optical waveguide.The technical scheme of the present application reconstructs target spectrum by introducing random defect to obtain scattered light on the surface of optical waveguide, has the advantages of few devices, compact spatial light path and small volume compared with traditional commercial spectrometer, which effectively reduces the system complexity and cost of spectrometer, improves the portability of spectrometer;When the structure uses the method of calculation reconstruction to reconstruct spectrum, it can well reproduce incident spectrum, and has large bandwidth and high spectral resolution.

Description

Technical Field

[0001] This invention relates to the field of spectrometer technology, and in particular to a defect scattering calculation and reconstruction spectral detection device and method. Background Technology

[0002] Spectroscopic analysis is an important technical means for observing the structure and composition of substances, and it is widely used in many scientific research fields such as physics, chemistry, astronomy, biomedicine, environmental monitoring, communications, national defense and security, as well as industrial and agricultural production.

[0003] Existing general-purpose spectrometers are mainly based on grating dispersion and Fourier transform. They are generally expensive to manufacture and maintain, and are large in size, which limits their application in many fields, such as in some functional optoelectronic chips and instruments where extremely compact spectrometers are required.

[0004] In recent years, various micro-nano spectroscopy technologies and chips have been extensively studied, such as the SWIFTS standing wave interferometer Fourier transform spectrometer. These spectral chips and instruments have almost no discrete components, are extremely small in size, have stable structures, and are low in cost, and are expected to become the most important option for the next generation of spectroscopy technologies and instruments. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a defect scattering calculation and reconstruction spectral detection device and method. This invention utilizes surface defects to obtain scattered light and employs spectral reconstruction to obtain the target spectrum. The reconstructed spectrum boasts high resolution and high speed. It eliminates the need for gratings, prisms, filters, or other spectroscopic components, resulting in fewer devices, a compact spatial optical path, and a near-zero size. This overcomes the shortcomings of traditional spectrometers, which require high precision of optical components, are bulky, expensive, and inconvenient to carry.

[0006] The technical solution adopted in this invention is as follows: a defect scattering calculation and reconstruction spectrum detection device, including a light scattering system and a detection system. The light scattering system includes a light guiding system, an optical waveguide and a surface random defect scattering array. The detection system is a photodetector, which is disposed on the optical waveguide and used to detect scattered light.

[0007] Preferably, the light guiding system is a single-mode waveguide. The width of the single-mode waveguide is such that light propagation is single-mode in the working band of the spectrometer. The thickness of the single-mode waveguide is the same as its width. The length of the single-mode waveguide can ensure that light propagates stably in single mode during propagation, thereby maintaining the stability of the input light field.

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

[0009] Preferably, the optical waveguide region is a flat multimode waveguide. Multimode interference mainly occurs in the transverse direction of the waveguide. The material of the multimode waveguide is the same as that of the single-mode waveguide. The material selected in this invention is silicon nitride. The material of the waveguide is a transparent material in the working band. Silicon nitride is used, but it is not limited to silicon, silicon dioxide, lithium niobate, group III-V semiconductor compounds or polymer materials.

[0010] Preferably, the defect is a random defect array, and the basic unit of the defect is a circle, but not limited to a circle. It can be a hexagon, pentagon, quadrilateral, cross, triangle or other regular or irregular shape, preferably a circle, and the defect appears as a sphere in three dimensions.

[0011] Preferably, the radius of the defect is a random value, and the basic array of defects is an N×M array, which is laid flat on the entire surface of the multimode waveguide. The position of each basic unit also has a random value in the length and width directions of the multimode waveguide. The random value refers to a random deviation near the originally regular array point position. This deviation does not exceed the distance between two adjacent defects in the basic array. The spherical center of each defect is located on the surface of the multimode waveguide, and the defect appears as a hemispherical depression on the waveguide surface, from which light is scattered.

[0012] A method for calculating and reconstructing spectroscopic detection using defect scattering, comprising the following steps:

[0013] 1) Calibration: Allow calibration light of known wavelengths and intensities within the band range to enter the device. The light is scattered from the side of the optical waveguide to obtain the light field intensity distribution on different pixels of the photodetector. Store the intensity values ​​obtained from this series of different wavelengths in the transmission matrix as the spectral response function.

[0014] 2) Acquiring the intensity distribution of the side-scattered light field: When light of an unknown spectrum enters the device, it is scattered from the side of the optical waveguide, thus obtaining the intensity distribution of the light field on the photodetector;

[0015] 3) Spectrum Reconstruction: The calibrated transfer matrix and the light field distribution of the unknown light form a linear equation. The reconstructed spectrum of the light under test is obtained by solving the linear equation.

[0016] Preferably, the photodetector collects the light signal scattered from the side of the optical waveguide.

[0017] Preferably, the equations used in the spectral reconstruction process are as follows:

[0018] I(x)=∫T(x,λ)S(λ)dλ

[0019] In the above formula:

[0020] S(λ): Spectral composition matrix of the input light;

[0021] T(x,λ): The transfer matrix of the device, the spectral response matrix of the device to be calibrated;

[0022] I(x): The light field intensity distribution matrix obtained at different positions of the detector.

[0023] Expanding this equation yields:

[0024]

[0025] Preferably, the detailed steps of the spectral reconstruction process are as follows:

[0026] 1. The transmittance function Tn at different positions of the device is obtained through calibration. Tn is the transmittance function of the nth spatial light spot channel. The wavelength S of the incident light is continuously adjusted to obtain m Tn samples with equal wavelength intervals. These Tn samples form 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.

[0027]

[0028] 2. To measure the device response to the light under test, the unknown light is introduced into the light-guiding system. After propagating to the optical waveguide region, the light is scattered from defects in the waveguide region, forming a light spot. The intensity In of the light spot can be obtained on the photodetector. In is the light field intensity at the nth pixel on the photodetector corresponding to the nth spatial spectral channel. The light field intensity distribution I is a one-dimensional matrix of length n.

[0029]

[0030] 3. Solve for the unknown spectrum. The unknown spectrum S is obtained by solving the linear equation system ST. -1 I is obtained. S is a matrix of length m:

[0031]

[0032] As a preferred option, m ≥ n.

[0033] The beneficial effects of this invention are as follows: When using the defect scattering calculation and reconstruction spectral detection device of this invention, it can operate in different wavebands for detection by reasonably selecting the detection area. Since it uses an optical waveguide as the main structure, the device is small in size, only a few square millimeters, which can reduce the size of the spectrometer. The defects used do not have high requirements for shape and position, because random quantities are added, so the requirements for manufacturing precision are not high. Due to the use of a large number of random defects, there is enough interference introduced by multimode interference, so the device has a sensitive spectral response, which enables the device to achieve a very high resolution. It is not only small in size but also meets the requirements for high-precision measurement. Furthermore, by integrating the detector with the device, the number of movable parts of the device is reduced, which greatly improves the integration and stability of the device. The feature structure of the device is relatively large, which is suitable for mass production and reduces the manufacturing cost of the device. It avoids the defects of traditional spectrometers, such as high precision requirements for optical components, large size, high cost and inconvenience. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a defect scattering calculation and reconstruction spectral detection device provided in an embodiment of the present invention.

[0035] Figure 2 A diagram of a random defect scattering structure provided in an embodiment of the present invention.

[0036] Figure 3 Spectral response diagrams of defects at different locations provided in embodiments of the present invention.

[0037] Figure 4 This is a schematic diagram of the broadband continuous spectrum and incident spectrum reconstructed according to an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the broadband equally spaced spectrum and incident spectrum reconstructed according to an embodiment of the present invention.

[0039] Figure 6 The smallest resolvable bispectral line reconstructed and recovered in an embodiment of the present invention.

[0040] In the figure, 1 is the photoelectric sensor; 2 is the light-guiding system; 3 is the multimode waveguide; 4 is the random defect scattering structure; and 5 is the substrate. Detailed Implementation

[0041] The present invention will be further described in detail below through specific embodiments:

[0042] 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.

[0043] like Figure 1 This illustrates the specific structure of a particular embodiment of the present invention. The defect scattering calculation and reconstruction spectral detection device of the present invention mainly consists of a photoelectric sensor 1, a light-guiding system 2, an optical waveguide 3, a random defect scattering structure 4, and a substrate 5. The light-guiding system 2 is connected to the optical waveguide 3, and the photoelectric sensor 1 is positioned directly above the multimode waveguide 3.

[0044] In use, the light-guiding system employs a single-mode waveguide, with fiber optic lenses used to couple the incident light. After propagating through the single-mode waveguide, the incident light stabilizes into single-mode light and then enters optical waveguide 3, which is a multimode waveguide. In the multimode waveguide, the light interferes and is then scattered from the random defect scattering structure 4. The defect scattering unit further affects the propagation of the light in the optical waveguide, thereby exhibiting a sensitive spectral response in the scattered light spot in the subsequent range of the multimode waveguide. The scattered light spot is received by photoelectric sensor 1. After calibrating the device, the spectrum of the unknown light can be obtained by using the light spot generated by the unknown light through a reconstruction algorithm.

[0045] In specific embodiments, both single-mode and multimode waveguides are made of silicon nitride. However, any material that remains transparent within the instrument's operating wavelength range can be used, except for silicon nitride. For example, silicon can be used as the waveguide material if it is used near the infrared band. The single-mode waveguide has a cross-sectional dimension of 0.2µm × 0.2µm and a length of 100µm. This is to ensure the stability of the input light within the device's operating wavelength range of 0.6-1.6µm. Within this range, the single-mode waveguide allows all wavelengths of input light to be coupled into single-mode light and then propagated. When input to the multimode waveguide, it maintains the stability of a single input light spot, thereby enhancing the stability of the device's response to each wavelength.

[0046] The multimode waveguide has a cross-sectional dimension of 0.5um × 8um and a waveguide length of 4500um. After light is introduced from the single-mode waveguide, it interferes in the multimode waveguide. The interference patterns of light of different wavelengths are different. After introducing randomly distributed defects, the differences between the interference patterns of light of different wavelengths become more obvious. The multimode waveguide serves as a carrier for random defect scattering.

[0047] like Figure 2 As shown, the random defect scattering structure has a basic unit of circularity, but is not limited to circularity. It can be hexagonal, pentagonal, quadrilateral, cross-shaped, triangular, etc., preferably circular. The defect appears as a sphere in three dimensions.

[0048] like Figure 3As shown, random defect structures distributed at different locations in a multimode waveguide will produce different spectral responses. When light propagates in the multimode waveguide, the random defect structures will scatter different spectral responses, and this structure will also affect the next propagation of light in the multimode waveguide, thereby increasing the spectral sensitivity of the corresponding defect structures behind it.

[0049] The radius of the defect is randomly 0.1-0.3 μm. The basic array of defects is a 5×1000 array, but the number is not limited to 5×1000. In actual use, in order to cover the entire surface of the multimode waveguide, 1.5 basic arrays are used, and the total number of defects is 5×1500. The spacing of the array units in the width direction is 1.6 μm, which is uniformly distributed in the width direction of the multimode waveguide. The spacing in the length direction is 3 μm, which is uniformly distributed in the length direction of the multimode waveguide. A random value is applied to the horizontal and vertical positions of each defect scattering unit of the array and the size of the defect, so that it becomes a rectangular random array with random size and random distribution. The position of each basic unit has a random value in both the width and length directions. The random value in the width direction is (-0.5 μm, 0.5 μm), and the random value in the length direction is (-2.8 μm, 2.8 μm).

[0050] The (-0.5um, 0.5um) random quantity refers to a random deviation near the originally regular array point position, and the range of this deviation is within the range of (-0.5um, 0.5um).

[0051] The spherical centers of the defects are all located on the surface of the multimode waveguide, and the defects appear as hemispherical depressions on the waveguide surface, from which light is scattered.

[0052] In a specific embodiment, the substrate and cladding of the single-mode and multi-mode waveguides are silicon dioxide, and the upper layer of the multi-mode waveguide is a silicon dioxide layer with a thickness of 300nm.

[0053] The waveguide is fabricated using plasma-enhanced chemical vapor deposition (PECVD), and the defect is fabricated using reactive ion etching (RIE). The gases used in RIE are SF6, N2, and O2. In dry etching, the active free radical molecules and atoms used in the etching process induce a chemical reaction, forming volatile substances that strip away the etchant. The free radicals are not affected by the electric field and are in thermal motion in all directions, making the etching isotropic and easily yielding the desired hemispherical defects.

[0054] The photoelectric sensor is a CMOS area array sensor. The distance between the CMOS area array sensor and the surface of the multimode waveguide is 300nm. After removing the protective glass of the CMOS area array sensor, the CMOS area array sensor is bonded to the silicon dioxide layer on the upper layer of the multimode waveguide.

[0055] The spectral reconstruction includes the following steps:

[0056] In a specific embodiment, a continuously adjustable light source is used to calibrate the device, and the equations used during calibration are as follows:

[0057] I(x)=∫T(x,λ)S(λ)dλ

[0058] In the above formula:

[0059] S(λ): Spectral composition matrix of the input light;

[0060] T(x,λ): The transfer matrix of the device, the spectral response matrix of the device to be calibrated;

[0061] I(x): The light spot intensity matrix obtained at different positions of the detector.

[0062] Expanding this equation yields:

[0063]

[0064] During calibration, a monochromatic light S with known wavelength and intensity is input. m The corresponding light intensity distribution I(x) can be obtained on the photodetector. Using these two known values, the components in the T(x,λ) transmission matrix can be determined. In use, within the device's operating wavelength range, the entire transmission matrix of the device is obtained by inputting monochromatic light with equally spaced wavelengths. m represents the number of spectral components, and n represents the number of pixels used in the photodetector calculation, where m ≥ n.

[0065] After calibrating the T(x,λ) transfer matrix, for the re-input unknown spectrum S(λ), the light spot intensity distribution function I(x) is obtained on the sensor through scattering from the side defects of the device. This is then solved by solving the equation S = T. -1 I can obtain the components of an unknown spectrum. For example... Figure 4 This image shows the spectral reconstruction result of the spectrometer on the input signal light. It represents a wide-band light reconstruction with a center wavelength of 830 nm and a spectral half-width of 15 nm, demonstrating its ability to reconstruct the target spectral lines remarkably well. Simulation experiments were conducted on light in the wavelength range of 0.6-1.4 μm, such as... Figure 5 and Figure 6 As shown, it can be seen that it can accurately reconstruct the target spectral lines within a wide bandwidth range, and can distinguish two spectral lines that differ by 0.2 nm at 850.8 nm, which is the resolution of the spectrometer.

[0066] Devices obtained through this method do not use beam splitters, have a wide operating band range, high and accurate resolution, small size and compact structure, low precision requirements in manufacturing processes, and are easy to produce.

[0067] The technical scope of this invention is not limited to the contents of the specification. The above embodiments are merely one example given to fully illustrate the principles and spirit of this invention. Those skilled in the art can make various changes and modifications to the described methods, and all such changes and modifications fall within the protection scope of this invention.

Claims

1. A defect scatter computed reconstruction spectroscopy apparatus, characterized by: The device comprises a photodetector, a light guiding system and a light waveguide. The light waveguide is a multimode waveguide with a random defect scattering structure etched on its surface and a cladding on the rest of the surface. The defect scattering structure is formed by loading a random quantity on the horizontal and vertical positions and size of each defect scattering unit based on a basic array. One end of the light guiding system is connected to a light source and the other end is connected to the light waveguide. The photodetector is arranged on the light waveguide to collect the light signal scattered from the side of the light waveguide for collecting the light spot scattered from the random defect scattering structure on the light waveguide. The light interferes in the multimode waveguide and is then scattered from the random defect scattering structure. The defect scattering unit further affects the propagation of the light in the light waveguide, thereby displaying a sensitive spectral response in the scattered light spot in the subsequent range of the multimode waveguide. The scattered light spot is received by the photodetector. After calibrating the device, the light spot generated by the unknown light can be obtained by a reconstruction algorithm to obtain the spectrum of the unknown light.

2. The defect scatter computed reconstruction spectroscopy apparatus of claim 1, wherein, The light guiding system is a structure that enables stable light after light propagation, so that the light spot and power of the light input into the light waveguide remain stable.

3. The defect scatter computed reconstruction spectroscopy apparatus of claim 2, wherein, The material of the waveguide is a transparent material in the working waveband, such as silicon nitride, silicon, silicon dioxide, lithium niobate, III-V semiconductor compounds or polymer materials or other materials that can be used to make an optical waveguide.

4. The apparatus of claim 3, wherein the apparatus is configured to perform the reconstruction of the spectrum of the scattered radiation by using a defect scattering calculation. The random defect scattering structure unit is an uneven structure on the side of the waveguide for the purpose of scattering light from the light waveguide. The defect cross section can be of any shape, and the three-dimensional shape can be a pit or a protrusion downward or upward from the surface of the waveguide.

5. The apparatus of claim 4, wherein the defect scattering computed reconstruction spectral probe is characterized by, The spatial position, size and depth of the basic unit of the random defect scattering structure have a random quantity, or one of them has a random quantity, or part of the total quantity has a random quantity. The obtained random defect scattering structure is randomly distributed on the surface of the light waveguide, and the light in the light waveguide propagates through the defect unit and is scattered out.

6. A method of defect scatter computed reconstruction spectroscopy, characterized by the steps of It comprises: 1) Calibration: let a calibration light with a certain wavelength and intensity in a waveband enter the device. The device is a defect scattering calculation reconstruction spectrum detection device according to any one of claims 1-5. The light is scattered from the side of the light waveguide, and the light field intensity distribution on different pixels of the photodetector is obtained. The light field intensity values obtained for a series of different wavelengths are stored in a transmission matrix as a spectral response function. 2) Collecting the light field intensity distribution of the side scattering: when the unknown light spectrum enters the device, the light is scattered from the side of the light waveguide, and the light field intensity distribution on the photodetector is obtained. 3) Reconstructing the spectrum: the calibrated transmission matrix and the light field distribution of the unknown light form a linear equation, and the reconstructed spectrum of the measured light is obtained by solving the linear equation.

7. The method of claim 6, wherein the method further comprises: The photodetector collects the light signal scattered from the side of the light waveguide.

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