Chip spectrometer and optical detection method

Abstract

The application discloses a chip spectrometer and a light detection method. The chip spectrometer comprises a detector and a light-proof layer, and has a dispersion structure and a light transmission structure or an output coupling structure; wherein, after the measured light is incident on the light-proof layer, the light is transmitted on a plane where the dispersion structure is located, coupled with the dispersion structure to realize dispersion, and then output to a light receiving surface of the detector through the light transmission structure or the output coupling structure. The chip spectrometer provided by the embodiment of the application has a small coverage area of the dispersion structure, can be completely integrated on the chip, and does not need evanescent wave coupling elements such as total reflection prisms.

Description

Technical Field

[0001] This invention relates to a spectrometer, and more particularly to a chip spectrometer and a light detection method, belonging to the field of detection equipment technology. Background Technology

[0002] Spectrometers are core equipment for material detection. Conventional spectrometers suffer from drawbacks such as large size, complex operation, and high cost. Miniaturized spectrometers, and even chip spectrometers, have significant advantages and market demand in scenarios such as lightweight platforms and rapid on-site detection. Current chip spectrometers include quantum dot spectrometers, planar cavity spectrometers, photonic crystal spectrometers, and metasurface spectrometers, but they generally suffer from challenges such as the difficulty in fabricating on-chip dispersive structures and insufficient spectral resolution. Summary of the Invention

[0003] The main objective of this invention is to provide a chip spectrometer and a photodetector method, thereby overcoming the shortcomings of the prior art.

[0004] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0005] This invention provides a chip spectrometer, comprising:

[0006] Detector, and

[0007] An opaque layer having a dispersive structure as well as a light-transmitting structure or an output coupling structure;

[0008] When the light to be measured is incident on the opaque layer, the light is transmitted on the plane of the dispersion structure and coupled with the dispersion structure to achieve dispersion. Then, it is output to the light-receiving surface of the detector through the light-transmitting structure or the output coupling structure.

[0009] This invention also provides a photodetector method, which is implemented based on the chip spectrometer, and the photodetector method includes:

[0010] The light to be measured is incident on the opaque layer and output to the light-receiving surface of the detector through a transparent structure or an output coupling structure, thereby realizing the imaging of the light field distribution. Then, the relationship between the wavelength of the light and the light field distribution is solved by the spectral reconstruction method, thus reconstructing the spectrum of the light to be measured.

[0011] Compared with the prior art, the advantages of the present invention include:

[0012] 1) The chip spectrometer provided in this embodiment of the invention has higher spectral resolution;

[0013] 2) The chip spectrometer provided in this embodiment of the invention has a small coverage area of ​​the dispersion structure. Moreover, the disordered dispersion structure (particles / voids) can be obtained by low-cost preparation processes such as nanosphere photolithography, rapid annealing, and chemical synthesis. The ordered dispersion structure (gradient periodic grating) is simpler to prepare than photonic crystals, metasurfaces and other solutions because of its small coverage area, thus having a low cost advantage.

[0014] 3) The chip spectrometer provided in this embodiment of the invention has a small coverage area of ​​the dispersive structure and is more integrated. It can be fully integrated on the chip without the need for evanescent wave coupling elements such as total reflection prisms. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a chip spectrometer provided in Embodiment 1 of the present invention;

[0016] Figure 2 This refers to the imaging on the detector array within a certain length of the light-transmitting structure of a chip spectrometer provided in Embodiment 1 of the present invention;

[0017] Figure 3a , Figure 3b Figure 3c These are images of different wavelengths of light being measured on the detector array of a chip spectrometer provided in Embodiment 1 of the present invention;

[0018] Figure 4 and Figure 5 These are the reconstructed spectra of the measured spectrum in Embodiment 1 of the present invention;

[0019] Figure 6 This is a schematic diagram of the structure of a chip spectrometer provided in Embodiment 2 of the present invention;

[0020] Figure 7 This is a schematic diagram of the structure of a chip spectrometer provided in Embodiment 3 of the present invention;

[0021] Figure 8 This is a SEM image of a graded periodic grating structure in a chip spectrometer provided in Embodiment 3 of the present invention;

[0022] Figure 9 The simulation results show the electromagnetic field intensity distribution obtained on the detector array when light of different wavelengths shines on the chip spectrometer in Example 3.

[0023] Figures 10a-10f These are the reconstruction results of different unknown spectra by analyzing the one-to-one correspondence between wavelength and image;

[0024] Figure 11 This is a schematic diagram of a graded periodic grating structure in a chip spectrometer provided in Embodiment 3 of the present invention;

[0025] Figure 12 This is a schematic diagram of the structure of a chip spectrometer provided in Embodiment 4 of the present invention. Detailed Implementation

[0026] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0027] This invention provides a chip spectrometer, comprising:

[0028] Detector, and

[0029] An opaque layer having a dispersive structure as well as a light-transmitting structure or an output coupling structure;

[0030] When the light to be measured is incident on the opaque layer, the light is transmitted on the plane of the dispersion structure and coupled with the dispersion structure to achieve dispersion. Then, it is output to the light-receiving surface of the detector through the light-transmitting structure or the output coupling structure.

[0031] In some specific embodiments, the dispersive structure is distributed on the surface and / or inside the opaque layer.

[0032] In some specific embodiments, the dispersive structure includes any one or more combinations of disordered particles and / or pores, and ordered gradient periodic grating structures.

[0033] In some specific embodiments, the size of the particle or hole in any direction is 0.2 to 2 times the wavelength of the light being measured.

[0034] In some specific embodiments, the period of the grating structure is 0.2-2 times the wavelength of the light being measured.

[0035] In some specific embodiments, the period of the grating structure gradually changes along a direction perpendicular to the periodic arrangement of the grating structure.

[0036] In some specific embodiments, the material of the dispersion structure can be a metal or a dielectric material, or even a material whose refractive index can be controlled by external signals such as light, electricity, and temperature. Preferred materials are noble metals (Au, Ag, Cu, Al) or metalloid materials (TiN, AZO, ITO) with surface plasmon resonance effects, or dielectric materials with a large difference in refractive index from the environment.

[0037] In some specific embodiments, the light-transmitting structure extends through the opaque layer along the thickness direction, and the size of the light-transmitting structure in at least one direction within the plane of the opaque layer is smaller than the wavelength of the light being measured, so as to suppress direct transmitted light, thereby reducing imaging correlation and improving spectral resolution.

[0038] In some specific embodiments, the light-transmitting structure includes a light-transmitting slit, which is covered by a light-blocking structure, and a gap is left between the light-blocking structure and the light-transmitting slit.

[0039] In some specific embodiments, a light-transmitting layer is distributed between the light-blocking structure and the light-transmitting slit.

[0040] In some specific embodiments, the light-transmitting slit can be any one or a combination of two or more of the following: strip-shaped, circular hole-shaped, square-shaped, and annular. For example, it can be combined into a square shape, etc.

[0041] In some specific embodiments, the light-blocking structure can be an opaque film material, for example, the material of the light-blocking structure can be a metal, a metal-like material or a dielectric material, specifically a metal or metal-like material reflector or a dielectric reflector.

[0042] In some specific embodiments, after the light to be measured is incident on the opaque layer, it is directly coupled to the dispersive structure; or, the opaque layer also has an input coupling structure, and after the light to be measured is incident on the opaque layer through the input coupling structure, it is coupled to the dispersive structure.

[0043] In some specific embodiments, the input coupling structure and the output coupling structure are offset from each other in any direction within the plane of the opaque layer.

[0044] In some specific embodiments, the opaque layer includes a first opaque layer and a second opaque layer arranged sequentially, with an optical cavity formed between the first opaque layer and the second opaque layer. The dispersive structure is distributed within the optical cavity, and the input coupling structure and the output coupling structure are respectively connected to the optical cavity to form a light transmission channel.

[0045] In some specific embodiments, the input coupling structure and the output coupling structure are distributed in the light-transmitting area within the opaque layer.

[0046] In some specific embodiments, the opaque layer is directly disposed on the light-receiving surface of the detector, or there is a gap between the opaque layer and the light-receiving surface of the detector.

[0047] In some specific embodiments, the material of the opaque layer can be metal, metal-like material or dielectric material, for example, the opaque layer can be a metal or metal-like material reflector or a dielectric reflector, etc.; the opaque layer can be directly prepared on the surface of the detector array, or it can be prepared on a transparent substrate (such as glass, ITO glass, etc.) and then attached to the surface of the detector array.

[0048] In some specific embodiments, the light-transmitting structure, the input coupling structure, and the output coupling structure all penetrate the opaque layer and are areas that allow light to pass through. For example, the input coupling structure and the output coupling structure can be structures such as slits or gratings set on the opaque layer, which will not be specifically limited or described here.

[0049] It should be noted that the light-transmitting layer material and the light-blocking layer material used in this invention need to be determined for different wavelengths of the measured light and selected according to specific circumstances. The chip spectrometer provided in this embodiment of the invention can be applied to the detection of measured light such as ultraviolet, visible, infrared, and terahertz. Taking the most common visible light band as an example, the opaque layer or light-blocking layer can be made of metal. Generally, metals above 100nm can achieve complete light blocking, and the maximum thickness of the metal light-blocking layer is about 500nm. However, if silicon is used as the opaque layer or light-blocking layer material, its required thickness will be much greater. Correspondingly, the light-transmitting layer also has the same problem. For example, glass is transparent in the visible light band, but it is not completely transparent for far-infrared light. Therefore, this embodiment of the invention does not limit the dimensions such as the thickness of the light-blocking structure, the light-transmitting layer, and the opaque layer.

[0050] In some specific embodiments, the detector can convert optical signals into electrical signals for output. The detector includes photodetectors and photothermal detectors, etc. The detector array can be a linear array or a surface array. Depending on the operating wavelength, it can be a detector array made of different materials, such as silicon detector arrays, indium gallium arsenide detector arrays, tellurium chromium mercury detector arrays, lead sulfide quantum dot detector arrays, etc.

[0051] This invention also provides a photodetector method, which is implemented based on the chip spectrometer, and the photodetector method includes:

[0052] The light to be measured is incident on the opaque layer and output to the light-receiving surface of the detector through a transparent structure or an output coupling structure, thereby realizing the imaging of the light field distribution. Then, the relationship between the wavelength of the light and the light field distribution is solved by the spectral reconstruction method, thus reconstructing the spectrum of the light to be measured.

[0053] In some specific embodiments, the light detection method includes: direct coupling of the light to be measured to the dispersive structure after incident on the opaque layer, or directing the light to be measured to the opaque layer through an input coupling structure and then coupling it to the dispersive structure.

[0054] The following will further explain the technical solution, its implementation process and principle in conjunction with the accompanying drawings and specific embodiments. Unless otherwise specified, the detectors and other components in the embodiments of the present invention may be those known to those skilled in the art.

[0055] The present invention provides a chip spectrometer in which the detector array is covered by an opaque layer, and the opaque layer contains a light-transmitting structure or an output coupling structure opposite to the detector.

[0056] The present invention also provides a method for optical detection using the chip spectrometer, which mainly includes: the light to be measured is incident on the input coupling structure and forms light that propagates in the plane of the metal micro-nano dispersion structure (the metal micro-nano dispersion structure and the input coupling structure are on the same substrate, and the metal micro-nano dispersion structure itself can also be used as the input coupling structure). During the in-plane propagation, the light is scattered, diffracted and interfered by the dispersion structure to form an in-plane light field distribution related to the wavelength. The light then reaches the detector array below through the output coupling structure (the output coupling structure and the metal micro-nano dispersion structure are on the same substrate), thereby realizing the imaging of the light field distribution. Then, the relationship between the wavelength and the light field distribution is solved by the spectral reconstruction method, thereby reconstructing the measured spectrum.

[0057] Example 1

[0058] Please see Figure 1 A chip spectrometer includes a detector array and an opaque layer. The opaque layer is disposed above the light-receiving surface of the detector array. The opaque layer has a dispersive structure and a transparent structure. After the light to be measured (also known as the incident light) is incident on the opaque layer, the light is formed and transmitted on the plane of the dispersive structure and coupled with the dispersive structure to achieve dispersion. Then, it is output to the light-receiving surface of the detector through the transparent structure or the output coupling structure.

[0059] In this embodiment, the detector array is a silicon detector array, and the opaque layer is a gold film with a thickness of 200nm. The gold film is directly disposed on the surface of the silicon detector array. The gold film has a U-shaped light-transmitting slit and gold nanoparticles disposed on the gold film. The size of the light-transmitting slit is subwavelength, and very little light is directly transmitted. The gold nanoparticles are distributed around the light-transmitting slit.

[0060] In this embodiment, the gold nanoparticles can be prepared by chemical synthesis, or gold nanoparticles can be prepared on the surface of the detector array by rapid thermal annealing, and then a gold film can be deposited to obtain a continuous gold film structure with undulating structure.

[0061] In this embodiment, the light being measured irradiates the gold nanoparticles, causing scattering and exciting surface plasmon resonance at certain wavelengths. These factors induce wavelength-sensitive electromagnetic field distributions at the light-transmitting slit, thus different spectral components of the incident light contribute differently to the imaging of corresponding parts of the detector array (e.g., Figure 2 As shown), this establishes a one-to-one correspondence between spectral information and imaging distribution. By resolving this relationship using a spectral reconstruction algorithm, the measured spectrum can be reconstructed (e.g., ...). Figure 4 and Figure 5 As shown in the figure, the images of the measured light at different wavelengths on the detector array are respectively as follows: Figure 3a , Figure 3b , Figure 3c As shown.

[0062] Example 2

[0063] Please see Figure 6 The structure of the chip spectrometer in this embodiment is basically the same as that in embodiment 1, except that the chip spectrometer in this embodiment also includes a light-blocking structure, the light-transmitting slit is covered by the light-blocking structure, and a light-transmitting layer is distributed between the light-blocking structure and the light-transmitting slit.

[0064] In this embodiment, the light-transmitting layer can completely cover the opaque layer, and the dispersion structure is disposed between the light-transmitting layer and the opaque layer.

[0065] In this embodiment, the material of the light-blocking structure can be the same as that of the opaque layer. The size of the opaque layer is sufficient to cover the light-transmitting slit, thereby completely avoiding direct light transmission. The size and material of the light-blocking structure can be adjusted according to specific needs.

[0066] Example 3

[0067] Please see Figure 7 and Figure 8 The structure of the chip spectrometer in this embodiment is basically the same as that in Embodiment 1, except that: the light-transmitting structure in this embodiment is a strip-shaped light-transmitting slit, and the dispersion structure in this embodiment has a certain regular morphology. The dispersion structure is a grating structure with a gradually changing period along the direction of the grating strip distributed on both sides of the strip-shaped light-transmitting slit. These gratings can couple incident light that satisfies the following wave vector matching conditions into the plane for transmission:

[0068] k0·sinθ+m·2π / P=k / /

[0069] Where k0 = 2π / λ, k0 is the wave vector of the measured light, λ is the wavelength of the measured light, θ is the angle of incidence, m is the grating order, P is the grating period, and k / / is the wave vector of the light propagating in the plane (which can be understood as dispersed light).

[0070] As can be seen from the above formula, the grating period determines the specific order of diffraction wavelength that can be excited. By gradually changing the grating period along the direction of the grating strips, different positions correspond to different diffraction wavelengths. In this way, incident light of different wavelengths can be coupled through the grating at different positions to achieve wave vector matching, and then reach the corresponding position of the detector array through the light-transmitting structure at that position, thereby forming different images.

[0071] In this embodiment, by pre-calibrating the light field distribution of different wavelengths of light on the detector array and analyzing the relationship between the light field distribution of the light to be measured on the detector array and the wavelength, the spectral information of the light to be measured can be obtained.

[0072] In this embodiment, the dispersion structure can also be as follows: Figure 11 The annular gradient periodic grating structure shown is... Figure 11 The gradient periodic grating structure shown is distributed on both sides of the light-transmitting slit. Of course, the gradient periodic grating structure can also be distributed only on one side of the light-transmitting slit.

[0073] Figure 9 Simulation results of electromagnetic field intensity distribution obtained on the detector array of the chip spectrometer in this embodiment under illumination with light of different wavelengths are shown. Figures 10a-10f It is the result of reconstructing different unknown spectra by analyzing the one-to-one correspondence between wavelength and image.

[0074] Example 4

[0075] Please see Figure 12 The structure of the chip spectrometer in this embodiment is basically the same as that in embodiment 1, except that: the opaque layer in this embodiment includes a first opaque layer and a second opaque layer arranged in sequence, an optical cavity is formed between the first opaque layer and the second opaque layer, the dispersion structure is distributed in the optical cavity, an input coupling structure is provided in the first opaque layer, and an output coupling structure is provided in the second opaque layer. The input coupling structure and the output coupling structure are respectively connected to the optical cavity and form a light transmission channel.

[0076] In this embodiment, the input coupling structure and the output coupling structure are offset from each other in any direction within the plane of the opaque layer.

[0077] In this embodiment, the incident light no longer directly illuminates the dispersive structure. Instead, it is converted into laterally propagated light by the input coupling structure and interacts with the dispersive structure during the lateral propagation process. Then, it enters the detector array via the output coupling structure. Since the upper and lower sides of the dispersive structure are opaque layers, all out-of-plane scattered light is reflected again and interacts with the dispersive structure. This back-and-forth scattering between the two opaque layers reduces the loss of out-of-plane scattering and improves optical efficiency, while also increasing the interaction between the light and the dispersive structure and improving spectral resolution.

[0078] In this embodiment, the spacing between the first opaque layer and the second opaque layer is larger than the thickness of the dispersive structure, and the difference between the spacing between the first opaque layer and the second opaque layer and the thickness of the dispersive structure does not exceed the wavelength of the incident light. The input / output coupling structure can be a slit or grating structure of various shapes such as strips or rings.

[0079] The chip spectrometer provided in this invention features an opaque layer. The image formed by the detector array is primarily composed of scattered, diffracted, or interfered light, unlike directly transmitted light (which can be simply referred to as direct transmission light). These lights interact with the dispersive structure, thus carrying wavelength-selective information (scattering, diffraction, and interference are all wavelength-sensitive optical behaviors). Consequently, the images formed by different wavelengths of the measured light have low correlation. In contrast, without the opaque layer, if the dispersive structure were placed directly on the detector array, the detector would receive a significant proportion of direct transmission light, resulting in a high wavelength correlation in the image of the light field distribution. This is because lower correlation helps to extract more accurate wavelength information from the measured signal. Therefore, the chip spectrometer provided in this invention has higher spectral resolution.

[0080] The chip spectrometer provided in this invention transmits the measured light in a plane after passing through an input coupling structure and interacts with a dispersive structure. The interaction distance is determined by the distance between the incident position of the measured light and the transmission structure or output coupling structure in the plane. In a design where the dispersive structure is placed directly on the detector array, the interaction distance between the light and the dispersive structure is determined by the thickness of the dispersive structure. Since the thickness of the dispersive structure is generally much smaller than the aforementioned distance, the interaction distance between the light and the dispersive structure is longer in this invention (Note: Although the interaction distance can be increased by thickening the dispersive structure, this increases the fabrication difficulty). A longer interaction distance allows for more complete spatial dispersion, which helps to reduce the wavelength correlation of the light field distribution. Therefore, the chip spectrometer provided in this invention has improved spectral resolution.

[0081] The chip spectrometer provided in this invention has a small coverage area of ​​dispersion structure, which is more integrated. Moreover, the disordered dispersion structure (particles / voids) can be obtained by low-cost fabrication processes such as nanosphere photolithography, rapid annealing, and chemical synthesis. The ordered dispersion structure (gradient periodic grating) is simpler to fabricate than photonic crystals, metasurfaces and other solutions due to its small coverage area, and has the advantage of low cost.

[0082] The present invention provides a chip spectrometer with a small coverage area of ​​dispersion structure and is more integrated. It can be fully integrated on a chip without the need for evanescent wave coupling elements such as total reflection prisms.

[0083] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A chip spectrometer, characterized in that, include: Detector, and An opaque layer has a dispersive structure and an output coupling structure. The dispersive structure includes any one or more combinations of randomly distributed particles and / or holes and an ordered gradient periodic grating structure. The opaque layer includes a first opaque layer and a second opaque layer arranged sequentially, with an optical cavity formed between the first opaque layer and the second opaque layer. The dispersive structure is distributed within the optical cavity. An input coupling structure is provided within the first opaque layer, and an output coupling structure is provided within the second opaque layer. The input coupling structure and the output coupling structure are respectively connected to the optical cavity to form an optical transmission channel. When the light to be measured is incident on the opaque layer, the light is transmitted on the plane of the dispersion structure and coupled with the dispersion structure to achieve dispersion. Then, it is output to the light-receiving surface of the detector through the output coupling structure.

2. The chip spectrometer according to claim 1, characterized in that: The output coupling structure extends through the opaque layer along the thickness direction, and the dimension of the output coupling structure in at least one direction within the plane of the opaque layer is smaller than the wavelength of the measured light.

3. The chip spectrometer according to claim 1, characterized in that: In any direction within the plane of the opaque layer, the input coupling structure and the output coupling structure are offset from each other.

4. The chip spectrometer according to claim 1, characterized in that: The input coupling structure and the output coupling structure are distributed in the light-transmitting area within the opaque layer.

5. The chip spectrometer according to claim 4, characterized in that: The opaque layer is directly disposed on the light-receiving surface of the detector, or there is a gap between the opaque layer and the light-receiving surface of the detector.

6. A photodetector method, characterized in that, The optical detection method is implemented based on the chip spectrometer described in any one of claims 1-5, and the optical detection method includes: The light to be measured is incident on the opaque layer and output to the light-receiving surface of the detector through the output coupling structure, thereby realizing the imaging of the light field distribution. Then, the relationship between the wavelength of the light and the light field distribution is solved by the spectral reconstruction method, thus reconstructing the spectrum of the light to be measured.

7. The optical detection method according to claim 6, characterized in that: The light detection method includes: causing the light to be measured to enter the opaque layer through an input coupling structure, and then coupling it with the dispersive structure.

Images