Spectral filters and spectrometers based on multi-stage resonant chamber structures

Abstract

The present invention relates to the art of spectral detection and discloses a spectral filter and spectrometer based on a multi-stage resonant chamber structure, which is arranged in a computational spectrometer when in use and has at least one optical path, wherein at least n+1 linearly arranged mirrors are provided in one optical path, n∈N and n≧2, and the mirrors have a reflectance of 5% to 50%. Resonant chambers are formed between two adjacent mirrors, and the linearly arranged n+1 mirrors constitute n stages of resonant chambers, the chamber length of each resonant chamber being 20μm to 2000μm, and the chamber lengths of at least two resonant chambers are different or the reflectances of at least two mirrors are different so that the n stages of resonant chambers can generate random transmission spectra in the frequency domain.

Description

Technical Field

[0001] This application relates to the technical field of spectrum detection, and specifically to a spectrum filter and a spectrometer based on a multi-stage resonance chamber structure.

Background Art

[0002] As a basic material analysis device, a spectrometer can effectively detect the physical and chemical components and properties of substances, and thus is widely applied in fields such as materials science, food safety, life and health, environmental monitoring, and aerospace.

[0003] Conventional spectrum detection methods mainly rely on a dispersive spectrometer based on a prism or a narrow-band filter and a Fourier transform spectrometer based on a Michelson interferometer.

[0004] Among these, a dispersive spectrometer decomposes a broadband input spectrum into each component in the frequency domain and detects them one by one by means of a detector array to obtain a complete input spectrum. In this method, since the power of the input beam must be decomposed proportionally, a large amount of energy loss is caused. This means that very high sensitivity and responsiveness are required for the detector array. Also, as the detection range and accuracy are extended, the number of detectors also increases proportionally, leading to an increase in cost.

[0005] A Fourier transform spectrometer uses the interference spectra in different optical path difference situations of an interferometer to encode the information of a broadband spectrum in the spatial domain. Thereby, the information of the entire input spectrum can be obtained using only a single detector, avoiding power loss. However, an interferometer usually requires scanning by mechanical parts for optical path difference adjustment, so it has a large structural volume, a long detection time, and a high cost. Also, the Fourier operation process of this method requires relatively large consumption of computing power resources.

[0006] In recent years, computational spectrometers have attracted widespread attention in academia and industry as a new method of spectral detection. Their basic principle involves introducing an input spectrum into multiple pre-calibrated broadband filter arrays and detecting the light intensity of the filtered spectrum using a corresponding number of photoelectric detectors. This intensity information is then used to construct a system of under-determined equations, which are solved using relevant algorithms to obtain information about the input spectrum. The advantage of this method is that it allows for the resolution of a large number of spectral pixels in the frequency domain using a relatively small number of filters and photoelectric detectors. This enables high spectral detection performance while reducing system volume, cost, and computational complexity.

[0007] The core design challenge of a computational spectrometer lies in designing its broad-spectrum filter array. From a mathematical standpoint, to obtain an ideal spectral detection effect, such a filter structure must satisfy the following two conditions: (1) The spectral response of each channel must have a relatively small autocorrelation coefficient to achieve high resolution. (2) A small cross-correlation coefficient between channels is required to guarantee the non-correlation of spectral sampling. This makes it possible to generate high-intensity random disturbances in the frequency domain, allowing for the construction and solution of effective under-determined simultaneous equations when using a computational spectrometer. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] This application aims to solve, to some extent, one of the technical problems in related technologies. Therefore, this application provides a spectral filter and spectrometer based on a multi-stage resonant chamber structure that can generate high-intensity random disturbances in the frequency domain based on the resonant chamber. [Means for solving the problem]

[0009] To achieve the above objective, the following technical solutions are employed in the first embodiment of this application.

[0010] A spectral filter based on a multi-stage resonant chamber structure is placed in a computational spectrometer when in use and has at least one optical path. In one optical path, at least n+1 linearly arranged mirrors are provided, where n∈N and n≧2. The aforementioned reflector has a reflectivity of 5% to 50%, A resonant chamber is formed between two adjacent mirrors. The n+1 mirrors arranged in a straight line constitute an n-stage resonant chamber. The chamber length of each resonant chamber is 20 μm to 2000 μm. The n-stage resonant chambers are configured such that they can generate random transmission spectra in the frequency domain, with at least two resonant chambers having different chamber lengths and / or at least two mirrors having different reflectivity.

[0011] By using multiple mirrors with different reflectivity or arranged linearly at unequal intervals, resonant chambers with varying reflectivity or chamber lengths are formed. As input light enters these resonant chambers, some of the light is transmitted and some is reflected each time it strikes a mirror. As the light passes through the multiple mirrors sequentially, these transmitted and reflected components interfere with each other, ultimately generating a nearly random transmission spectrum in the frequency domain at the output terminal. This allows for the construction and solving of effective deficiency-determined simultaneous equations when using a computational spectrometer.

[0012] According to the present invention, more preferably, the reflectance of the reflector is 10% to 20%.

[0013] According to the present application, more preferably, n is 5, 6, 7, or 8.

[0014] The present invention more preferably includes an optical waveguide device in which a one-dimensional photonic crystal is provided so as to form the reflector.

[0015] Preferably, the system includes a plurality of substrates on which an optical coating having reflectivity is coated on the surface, The optical coating constitutes the reflecting mirror.

[0016] Preferably, the optical fiber includes a Bragg grating provided so as to constitute the reflector.

[0017] According to the present application, more preferably, the optical fiber is a multicore optical fiber, A Bragg grating is provided within each core so as to constitute the aforementioned reflector.

[0018] According to the present invention, more preferably, the reflectance of the reflector is 10% to 20%.

[0019] According to the present application, more preferably, there are at least M optical paths, Each optical path is provided with n stages of the aforementioned resonant chambers. In M optical paths, the n-stage resonant chambers of each optical path generate different transmission spectra depending on the settings of the chamber length and / or the reflectance of the mirrors.

[0020] Furthermore, according to a second aspect of the present application, a spectrometer is provided that includes a broadband light source, a photoelectric detector array, and the spectral filter described in the first aspect. The broadband light source and the photoelectric detector array are provided at both ends of the spectral filter, The number of photoelectric detectors in the aforementioned photoelectric detector array is the same as the number of optical paths in the aforementioned spectral filter. The beneficial effects of the spectrometer provided by this application are similar in reasoning to those of the spectral filter described above, and therefore will be omitted here.

[0021] Furthermore, according to a third aspect of the present application, a spectrometer is provided that includes a broadband light source, a photoelectric detector, and the spectral filter described in the first aspect. The broadband light source and the photoelectric detector array are provided at both ends of the spectral filter, The spectrometer further includes a microelectromechanical system, The microelectromechanical system includes a microactuator array used to form an adjustable resonance chamber by moving a mirror in the optical path propagation direction by a microactuator to change the distance between the mirrors.

[0022] Furthermore, the spectral filter has only a single optical path.

[0023] These features and advantages of the present application are disclosed in detail in the following specific embodiments and the accompanying drawings. The optimal embodiments or solutions of the present application are described in detail in relation to the accompanying drawings, but do not limit the technical solutions of the present application. Also, these features, elements, and components appearing in the following description and drawings are plural, and for the convenience of illustration, are assigned different reference signs or numbers, but all represent components having the same or similar configurations or functions.

Brief Description of the Drawings

[0024] Hereinafter, the present application will be further described with reference to the drawings. [Figure 1] It is a schematic diagram of the principle of the spectral filter in the present application. [Figure 2] It is a transmission spectrum graph of the spectral filter based on a multi-stage resonance chamber. [Figure 3] It is a schematic diagram of the structure of the spectral filter in one exemplary embodiment. [Figure 4] It is a schematic diagram of the structure of the spectral filter in one exemplary embodiment. [Figure 5] It is a schematic diagram of the structure of the spectral filter in one exemplary embodiment. [Figure 6] It is a schematic diagram of the structure of the spectral filter in one exemplary embodiment. [Figure 7] It is a schematic diagram of the structure of the spectrometer in one exemplary embodiment. [Figure 8]This is a schematic diagram of the structure of a spectrometer in one exemplary embodiment. [Figure 9] This is a schematic diagram of the structure of a spectrometer in one exemplary embodiment. [Figure 10] This is a spectral recovery effect diagram of a computational spectrometer constructed using a 16-channel multi-stage resonant chamber filter in one exemplary embodiment. [Modes for carrying out the invention]

[0025] The embodiments of this application will be described in detail below. Examples of the above embodiments are shown in the accompanying drawings, and throughout the drawings, the same or similar reference numerals indicate the same or similar elements, or elements having the same or similar functions. The embodiments described are for illustrative purposes of this application and should not be understood as limitations to this application.

[0026] The terms “one embodiment,” “example,” or “example” as used herein mean that certain features, structures, or characteristics described in relation to the embodiment itself may be included in at least one embodiment disclosed herein. Where the phrase “in one embodiment” appears in the specification, it does not necessarily refer to the same embodiment.

[0027] Figure 1 shows a schematic diagram of the principle of a spectral filter based on a multi-stage resonant chamber structure in this application. This spectral filter based on a multi-stage resonant chamber structure is placed in a computational spectrometer when in use and has at least one optical path. In the figure, one optical path will be explained as an example.

[0028] This optical path is provided with at least n+1 linearly arranged mirrors, where n∈N and n≧2. The direction of arrangement is the direction of propagation of the optical path, and in the diagram, the left side of the spectral filter is the input end of the spectrum, and the right side is the output end. The mirrors have reflectances of 5% to 50%. By linearly arranging mirrors with preferentially different reflectances, the intensity of random disturbances during light propagation is improved.

[0029] A resonant chamber is formed between two adjacent mirrors, and n+1 mirrors arranged in a straight line can form n stages of resonant chambers. The chamber length of each resonant chamber is between 20 μm and 2000 μm, and at least two of the resonant chambers have different chamber lengths. To achieve a better effect, the lengths of each chamber should be made as different as possible from each other to increase the intensity of random disturbances during the propagation of light.

[0030] For the input spectrum on the left, after entering this chamber, some of the light is transmitted and some is reflected each time it hits the mirror. In the figure, the transmitted light is E + The reflected light is, the cursor is E - As shown, in the process of passing sequentially through multiple mirrors, these transmitted and reflected components interfere with each other, ultimately generating a nearly random transmission spectrum in the frequency domain at the output end. There are three main factors that influence random disturbances. The first is the number of mirrors, i.e., the number of resonant chambers. The second is the difference between the reflectances of each mirror. The third is the difference between the chamber lengths of each resonant chamber. The more mirrors there are, the larger the differences in reflectance and chamber length become, and ultimately the higher the intensity of random disturbances in the output spectrum at the output end.

[0031] Mathematically, the projection (i.e., transmission, i.e., refraction through a mirror) or reflection spectrum of such a resonant chamber structure can be described by the transfer matrix method.

number

[0032] Here,

number

number

number

number

[0033] Using this formula, the transmission spectrum of a multi-stage resonant chamber can be expressed by the sequential multiplication of this matrix. As can be seen from related calculations, when there are two mirrors, the resonant chamber outputs a periodically changing transmission spectrum. On the other hand, when the number of mirrors exceeds three, the periodicity of the output spectrum can be effectively broken, and a near-random spectral disturbance is formed.

[0034] Specifically, when the reflectivity of each mirror is between approximately 5% and 50%, and the distance between two mirrors (i.e., the length of each chamber) is between tens and thousands of micrometers, the resulting spectral disturbance is relatively ideal in terms of both the range and rate of variation. As the number of resonant chambers increases, the disturbance density increases.

[0035] Figure 2 shows the transmission spectrum graph of a spectral filter with a five-stage resonant chamber structure based on an integrated optical waveguide device. The reflectivity of a single mirror is 10% to 20%, and the chamber length is 50 to 200 μm. As can be seen from the figure, the transmission spectrum of this spectral filter has high random disturbance.

[0036] The following section describes in detail a spectral filter with a multi-stage resonant chamber structure and a method for constructing a spectrometer using this spectral filter, in relation to different mirror structures.

[0037] Example 1 Figure 3 shows a spectral filter based on a multi-stage resonant chamber structure. The spectral filter 100 is implemented using an optical waveguide device 110 in an integrated optical platform. In this embodiment, the case of a single optical path is described as an example. Depending on the actual requirements, multiple optical paths may be employed, and an optical waveguide device based on a multi-stage resonant chamber structure may be provided for each optical path.

[0038] Specifically, partial reflection of light is achieved by etching a portion of the Bragg grating 111 onto an optical waveguide device 110 (structure) made of materials such as silicon / silicon nitride / InP. The Bragg grating is a periodic structure, and by applying a periodic change in refractive index to the optical waveguide (device) through methods such as etching, reflection of a specific intensity for light of a specific wavelength is achieved. The specific reflection intensity and the center wavelength of reflection can all be effectively controlled by parameters such as the period length, number of periods, and refractive index difference of the grating. Based on this method, as described above, by setting the reflectivity of each Bragg grating region (the formed mirror) to a range of approximately 10% to 20% and controlling the distance between the two mirrors (i.e., the chamber length) to between tens and hundreds of micrometers, a relatively good random spectral disturbance effect can be achieved.

[0039] In addition to the above-mentioned solutions, those skilled in the art can also achieve partial reflection of light using a one-dimensional nanobeam photonic crystal structure (reflector) as an alternative to etching the Bragg grating. On the other hand, a one-dimensional photonic crystal (nanobeam) structure is similarly a structure with a periodic change in refractive index, and its basic principle is to reflect light of a specific wavelength with a specific reflectivity by forming a forbidden band based on the adjustment and control of the photonic bandgap. The specific reflectivity can similarly be effectively adjusted and controlled by the nanobeam structure parameters (e.g., the geometric parameters and period length of the crystal). Similarly, based on such a method, as described above, a relatively good random spectral disturbance effect can be achieved by setting the reflectivity of each photonic crystal reflector in the range of about 10% to 20% and controlling the distance between the two reflectors (i.e., the chamber length) to between tens and hundreds of micrometers.

[0040] As shown in Figure 4, in one exemplary embodiment, a similar resonant chamber structure may be formed within the photosensitive optical fiber 120. The fabrication method is similar to that of a conventional optical fiber Bragg grating. The refractive index of the photosensitive optical fiber can be changed by irradiation with UV light. By designing the period and duty cycle of the grating 121, a grating 121 with a desired reflectance / transmittance can be obtained. By connecting multiple gratings 121 in multiple stages, a complex response spectrum can be obtained.

[0041] As shown in Figure 5, in addition to the single-channel photosensitive optical fiber described above, if the spectral filter requires multiple optical path channels, multiple optical fibers with special response spectra may be designed, and the n-stage resonant chambers of each optical path are different from each other so that different transmission spectra are generated in each optical path. These multiple optical fibers can be manufactured within the same structure by directly drawing a multicore form or by joining multiple fibers, and are called multicore optical fibers. The spectrum to be measured is incident on one end of the multicore optical fiber, a photoelectric detector array is connected to the other end to detect the spectral signal, and finally, an intensity information recovery spectrum is obtained.

[0042] Example 2 Figure 6 shows a spectral filter based on another multi-stage resonant chamber structure. This spectral filter realizes the multi-stage optical resonant chamber structure using an optical coating method on a free-space optical platform.

[0043] The figure shows only a multi-stage resonant chamber structure on a single optical path. Specifically, a reflector with partial reflectivity and partial transmittance is realized by coating the surface of a substrate (e.g., optical glass or quartz glass) with a specific coating material (e.g., a dielectric material coating consisting of oxides, fluorides, silicon, etc.). Here, the specific reflectivity and transmittance of the reflector can be effectively controlled by adjusting the coating thickness, the proportion of material components, etc.

[0044] By fabricating multiple such coated mirrors and arranging them at different intervals (i.e., chamber lengths), the multi-stage resonant chamber filter proposed in this invention can be realized. Similarly, in order to obtain a relatively good disturbance effect, the reflectivity of each coated mirror may be set to between approximately 10% and 20%, and the interval between two mirrors (i.e., the chamber length) may be set to between several tens and several hundred micrometers.

[0045] In this specification, the reflector is a coating applied to the surface of the substrate. The substrate is glass, and its thickness can reach several tens of micrometers. Furthermore, since there is little effect on the spectrum when passing through the glass substrate, the chamber length here actually includes the thickness and spacing of the glass.

[0046] Example 3 Figure 7 shows a chip-scale computational spectrometer. This chip-scale computational spectrometer includes a broadband light source, a spectral filter 100 based on a multi-stage resonant chamber structure, and a photoelectric detector array 200. The broadband light source is located at the input end of the spectral filter, and the photoelectric detector array 200 is located at the output end of the spectral filter 100.

[0047] This spectral filter employs the multi-stage resonant chamber structure proposed in Example 1 within an integrated optical platform, and differs in that it employs multiple optical paths, with each optical path provided with an optical waveguide device 110 with a multi-stage resonant chamber structure.

[0048] Here, the input light is introduced to an integrated optical chip by means of a port coupler or grating coupler, then split into multiple input light streams, introduced into multi-stage resonant chambers with different optical paths on a spectral filter, and finally measured by an on-chip or off-chip photoelectric detector array. Because the transmission response of each resonant chamber filter is different from that of the others, the input spectrum can be calculated from the photoelectric detector readings to achieve the objective of spectral detection. Here, the unknown sample to be detected may be placed between the multi-chamber structure and the light source, or between the multi-chamber structure and the photoelectric detector. The drawings only show the configuration in which the sample is placed between the multi-chamber structure and the light source.

[0049] Example 4 Figure 8 shows another computational spectrometer. This spectrometer includes multiple broadband light sources, a spectral filter based on a multi-stage resonant chamber structure, and a photoelectric detector array. The broadband light sources are located at the input end of the spectral filter, and the photoelectric detector array is located at the output end of the spectral filter.

[0050] This spectral filter employs the multi-stage resonant chamber structure proposed in Example 2 in free space, but differs in that it employs multiple optical paths, each of which is provided with a multi-stage resonant chamber structure. Accordingly, the number of broadband light sources and the number of photoelectric detectors in the photoelectric detector array are the same as the number of optical paths.

[0051] In this embodiment, the same light source is used for multiple broadband light sources and is input in parallel to multiple optical path resonant chambers. The filtered light intensity is similarly detected by a photoelectric detector array, and the input spectrum is then calculated in reverse. Similarly, the unknown sample to be detected may be placed between the multi-chamber structure and the light source, or between the multi-chamber structure and the photoelectric detector. The drawings only show the configuration in which the sample is placed between the multi-chamber structure and the light source.

[0052] In addition to employing multiple broadband light sources as described above, an alternative embodiment employing only a single broadband light source is also possible, and a detailed explanation of this is omitted here.

[0053] Example 5 Figure 9 shows another computational spectrometer. The spectrometer described in this embodiment differs from the spectrometer described in Embodiment 4 in that the spectral filter employs only a single optical path, and accordingly, only a single broadband light source and photoelectric detector are provided. The spectrometer in this embodiment further includes a microelectromechanical system. The microelectromechanical system includes a microactuator array used to form an adjustable chamber body by moving the mirrors in the optical path propagation direction using microactuators to change the spacing between the mirrors. The number of microactuators is at least one and at most equal to the number of mirrors in the spectral filter. To achieve the maximum number of adjustments, in this embodiment, one mirror is not positioned as the origin of the reference coordinate system, while the remaining mirrors are fixed one by one to their corresponding microactuators. When the microactuators operate, they adjust the chamber length of the resonant chamber by moving the mirrors fixed to them in the direction along the optical path. By adjusting to different chamber lengths, the function of a multi-path spectrometer can be achieved by performing multiple measurements.

[0054] Example 7 This embodiment provides a computational spectrometer using a 16-channel multi-stage resonant chamber filter.

[0055] Figure 10 shows the spectral recovery effect of a computational spectrometer constructed using a 16-channel multi-stage resonant chamber filter. As can be seen from the figure, the recovered spectrum and the actual input spectrum show a high degree of agreement, demonstrating the high accuracy of spectral detection. Specifically, in this example, the bandwidth reaches 120 nm and the accuracy reaches 0.5 nm. That is, more than 240 spectral pixel points can be obtained in the measured wavelength range of 1480 nm to 1600 nm.

[0056] The above are merely specific embodiments of the present application and do not limit the scope of protection. Those skilled in the art will understand that the present application includes, but is not limited to, the drawings and the above-described specific embodiments. Any modifications that do not depart from the functional and structural principles of the present application are included in the claims. [Explanation of Symbols]

[0057] 100 spectral filters 110 Optical waveguide devices 111 Bragg Grating 120 optical fibers 121 Gratings 200 Photoelectric Detector Array 310 Microactuators

Claims

1. A spectral filter based on a multi-stage resonant chamber structure, which is placed in a computational spectrometer during use and has at least one optical path, In one optical path, at least n+1 linearly arranged mirrors are provided, where n ∈ N and n ≥ 2. The aforementioned reflector has a reflectivity of 5% to 50%, A resonant chamber is formed between two adjacent mirrors. The n+1 linearly arranged mirrors constitute an n-stage resonant chamber. The chamber length of each resonant chamber is 20 μm to 2000 μm. The n-stage resonant chambers are capable of generating random transmission spectra in the frequency domain if at least two of the resonant chambers have different chamber lengths and / or at least two of the mirrors have different reflectivity. Spectral filter.

2. n is 5, 6, 7, or 8. The spectral filter according to claim 1.

3. The optical waveguide device includes a Bragg grating formed on which the reflector is formed, The spectral filter according to claim 1.

4. The optical waveguide device includes a one-dimensional photonic crystal provided so that the reflecting mirror is formed, The spectral filter according to claim 1.

5. It includes a plurality of substrates on which an optical coating having reflectivity is applied to the surface, The optical coating constitutes the reflecting mirror, The spectral filter according to claim 1.

6. Including an optical fiber provided with a Bragg grating so as to constitute the aforementioned reflector, The spectral filter according to claim 1.

7. The optical fiber is a multicore optical fiber, A Bragg grating is provided within each core so as to constitute the reflector. The spectral filter according to claim 6.

8. The reflectivity of the aforementioned mirror is 10% to 20%. The spectral filter according to claim 1.

9. Having at least M optical paths, Each optical path is provided with the aforementioned n-stage resonant chambers. In M optical paths, the n-stage resonant chambers of each optical path generate different transmission spectra depending on the settings of the chamber length and / or the reflectance of the mirror. A spectral filter according to any one of claims 1 to 6.

10. A broadband light source, a photoelectric detector array, and a spectral filter according to any one of claims 1 to 8, The broadband light source and the photoelectric detector array are provided at both ends of the spectral filter, The number of photoelectric detectors in the aforementioned photoelectric detector array is the same as the number of optical paths in the aforementioned spectral filter. Spectrometer.

11. A broadband light source, a photoelectric detector, and the spectral filter described in claim 5, The broadband light source and the photoelectric detector are each provided at both ends of the spectral filter. The spectrometer further includes a microelectromechanical system, The micro-electromechanical system includes a microactuator array used to form an adjustable resonant chamber by moving the reflectors in the optical path propagation direction using microactuators to change the distance between the reflectors. Spectrometer.

12. The spectral filter has only a single optical path. The spectrometer according to claim 11.

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