Multi-pass optical filter and preparation method thereof

Abstract

The invention discloses a multi-pass optical filter and a preparation method thereof, and the method comprises the steps: selecting a main reference channel, and carrying out the difference frequency modulation excitation through narrow linewidth laser, and obtaining optical transmission coupling data; performing periodic disturbance detection on the observation channel to obtain spectrum drift associated data; modulating deposition power and air pressure according to the spectrum drift associated data to form a crosstalk suppression layer; forming a three-layer dielectric structure with increasing optical thickness and a periodically changing coupling regulation layer on the crosstalk suppression layer; and performing temperature modulation annealing treatment to form an inter-channel steady-state coupling structure, and establishing a spectrum drift compensation parameter. The technical scheme of the invention can systematically characterize the correlation drift of the multi-channel spectral characteristic along with the micro process or service disturbance, accurately quantify the coupling relationship between different passbands, and solve the technical problem that the correlation drift between the passbands cannot be completely captured in the existing discrete measurement mode. The phenomenon of'array misfocus' in a miniature multispectral system is effectively avoided, and the precision and stability of the multi-pass optical filter are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-pass filter preparation, and particularly to a multi-pass filter and a preparation method thereof. Background Art

[0002] A multi-pass filter is a complex multi-layer thin film optical element. Its core structure is precisely stacked by multiple groups of alternating high and low refractive index thin film layers, forming multiple independent passbands, which can simultaneously selectively transmit or reflect light in a specific wavelength range. Each passband is usually composed of a specific multi-cavity Fabry-Perot interference structure. These cavities are interconnected through a common film system and share some film layers, so that while realizing the spectral selection function of multiple passbands, it also has the advantages of compact structure and sharp spectral response, and is widely used in miniature multispectral systems.

[0003] In the existing preparation process of multi-pass filters, a single-channel discrete measurement mode is mainly used for process control, that is, during the film deposition process, a spectral analyzer or a monochromator is used to independently measure and characterize the spectral characteristics of each passband, and calibration is carried out under fixed environmental conditions. However, due to the fact that the multi-cavity structure of the multi-pass filter is physically coupled through a common film system, there is an inherent correlation between the passbands. When the filter undergoes minute perturbations such as nanoscale thickness ripples, thermal stress redistribution, or interface microstructure evolution, the spectral characteristics of one passband shift, which will cause the other passbands to drift synchronously in a non-linear but predictable functional relationship. This phenomenon is difficult to be completely captured in the traditional discrete measurement mode because the traditional method regards each passband as an independent unit that is not related to each other, lacks the ability to project the instantaneous drift into a high-dimensional correlation space, and cannot quantify the coupling relationship between the passbands. With the continuous improvement of the accuracy requirements of the filter in the miniature multispectral system, this measurement breakage leads to the phenomenon of "whole-column defocusing" in the subsequent application of the device, that is, multiple channels drift simultaneously, but due to the lack of a corresponding drift coupling model and prediction mechanism, it becomes extremely difficult to trace the source and compensate for the deterioration of the system performance. Therefore, there is an urgent need for a preparation method that can systematically characterize the correlated drift of multi-channel spectral characteristics with minute process or service perturbations to solve the technical problem that the existing technology cannot simultaneously capture and quantify the coupling relationship between the passbands. Summary of the Invention

[0004] The main purpose of the present invention is to solve the problem that under minute process or service perturbations, the multi-channel spectral characteristics of the multi-pass filter will produce correlated drift, while the existing detection means cannot simultaneously capture and quantify this drift.

[0005] In the first aspect of the present invention, a preparation method of a multi-pass filter is provided. The preparation method of the multi-pass filter includes: Select the main reference channel, and use a narrow-linewidth laser to perform difference-frequency modulation excitation on the main reference channel to obtain the optical transmission coupling data between the main reference channel and the observation channel; According to the optical transmission coupling data, perform periodic perturbation detection on the observation channel to obtain the spectral drift correlation data between channels; According to the spectral drift correlation data, modulate the deposition power and gas pressure during the film deposition process to form a crosstalk suppression layer between channels; According to the spectral drift correlation data, form a three-layer dielectric layer structure with gradually increasing optical thickness on the crosstalk suppression layer, and set a periodically varying coupling control layer between the dielectric layer structures of different channels; Perform temperature modulation annealing treatment on the multi-pass filter to form a steady-state coupling structure between channels and establish spectral drift compensation parameters.

[0006] Preferably, the selection of the main reference channel, using a narrow-linewidth laser to perform difference-frequency modulation excitation on the main reference channel to obtain the optical transmission coupling data between the main reference channel and the observation channel includes: Select the central channel as the main reference channel based on the correlation analysis of spectral transmittance and central wavelength, and determine the channels with shared film layers with the main reference channel as the observation channels; Modulate the narrow-linewidth laser into multiple difference-frequency waveforms, and establish a one-to-one correspondence between the frequency distribution of the difference-frequency waveforms and the phonon resonance frequencies of the observation channels; Excite phonon resonance in the main reference channel according to the difference-frequency waveforms and record the frequency response characteristics of the phonon resonance; Adjust the frequency response characteristics of the phonon resonance to form a phonon propagation channel in the shared film layer between the main reference channel and the observation channel, and obtain the phonon propagation intensity distribution; Based on the phonon propagation intensity distribution, control the directionality of the phonon propagation channel and establish a directional energy transmission path from the main reference channel to the observation channel; Record the optical intensity attenuation coefficient and phase delay parameters in the directional energy transmission path respectively to form the optical transmission coupling data.

[0007] Preferably, the control of the directionality of the phonon propagation channel based on the phonon propagation intensity distribution to establish a directional energy transmission path from the main reference channel to the observation channel includes: Perform Fourier transform on the phonon propagation intensity distribution according to the spatial distribution characteristics to obtain the phonon wave vector distribution data; Perform polarization state modulation on the phonon propagation channel according to the phonon wave vector distribution data to obtain the phonon polarization direction map; Perform phonon wavefront modulation on the film layer interface of the main reference channel according to the phonon polarization direction map and the phonon wave vector distribution data to form a phonon transmission channel; Use the phonon transmission channel to couple the energy of the main reference channel and the observation channel to establish a directional energy transmission path.

[0008] Preferably, perform periodic perturbation detection on the observation channel according to the optical transmission coupling data to obtain spectral drift correlation data between channels, including: Construct the spectral response spatial distribution of the observation channel according to the light intensity attenuation coefficient and phase delay parameter of the optical transmission coupling data; Based on the spectral response spatial distribution, apply a periodically varying angular perturbation wave in the observation channel to obtain the relationship between the transmitted light intensity and the angle; According to the relationship between the transmitted light intensity and the angle, modulate the frequency of the angular perturbation wave to the frequency corresponding to the trough of the transmitted light intensity wave, and record the light intensity response curve; According to the light intensity response curve, determine the standing wave frequency of the angular perturbation wave in the observation channel, and establish a frequency response network for the observation channel; Modulate the light field phase between different observation channels through the standing wave frequency in the frequency response network to obtain the phase correlation data between channels; Determine the timing relationship of spectral drift between observation channels according to the phase correlation data to form spectral drift correlation data between channels.

[0009] Preferably, the determining the standing wave frequency of the angular perturbation wave in the observation channel according to the light intensity response curve and establishing a frequency response network for the observation channel includes: Perform wavelet transform decomposition on the light intensity response curve to obtain frequency component data; Calculate the standing wave node positions in the observation channel according to the frequency component data to form a standing wave distribution map; Perform phase compensation calculation according to the standing wave distribution map and the frequency component data to obtain the standing wave frequency parameter; Use the standing wave frequency parameter to perform frequency response modulation on the observation channel to establish a frequency response network.

[0010] Preferably, modulating the deposition power and gas pressure during the film layer deposition process according to the spectral drift correlation data to form a cross-talk suppression layer between channels includes: Analyze the drift frequency difference between adjacent observation channels in the spectral drift correlation data, and divide the film layer deposition process into multiple deposition cycles according to the magnitude of the frequency difference; Set different deposition power modulation frequencies for each deposition cycle to form a power modulation curve opposite to the drift frequency of the observation channel, and record the deposition power compensation data; According to the deposition power compensation data, calculate the air pressure modulation amplitude of each deposition cycle, form an air pressure fluctuation gradient between adjacent deposition cycles, and obtain an air pressure modulation curve; According to the air pressure modulation curve, form a periodic structure with alternating refractive indices during the film deposition process, and measure the refractive index change amplitude; According to the refractive index change amplitude, divide the stress transition region between adjacent observation channels, and record the stress distribution gradient; Perform hierarchical modulation on the stress distribution gradient according to the drift frequency difference, and form an inter-channel crosstalk suppression layer in the film.

[0011] Preferably, the step of dividing the stress transition region between adjacent observation channels according to the refractive index change amplitude and recording the stress distribution gradient includes: Perform stress field decomposition on the refractive index change amplitude to obtain the principal stress component data; Calculate the stress transfer coefficient between adjacent observation channels according to the principal stress component data to form a stress transfer matrix; Perform boundary stress calculation on the stress transition region according to the stress transfer matrix and the principal stress component data to obtain stress transition parameters; Use the stress transition parameters to perform stress distribution calculation between adjacent observation channels, and record the stress distribution gradient.

[0012] Preferably, the step of forming a three-layer dielectric layer structure with gradually increasing optical thickness on the crosstalk suppression layer and setting a periodically varying coupling control layer between the dielectric layer structures of different channels according to the spectral drift correlation data includes: Calculate the spectral drift compensation amount between observation channels according to the phase correlation data in the spectral drift correlation data to obtain the optical path difference compensation parameter; Based on the optical path difference compensation parameter, sequentially deposit a first dielectric layer, a second dielectric layer, and a third dielectric layer on the crosstalk suppression layer, and record the thickness gradient data of the three dielectric layers; Analyze the thickness gradient data of the three dielectric layers to obtain the optical path difference change curve between the dielectric layers, and record the optical path difference distribution data; Calculate the periodic modulation parameter between adjacent observation channels according to the optical path difference distribution data to form a periodic thickness change sequence; Deposit a coupling control layer between the three-layer dielectric structures of adjacent observation channels according to the thickness change sequence.

[0013] Preferably, the step of performing temperature modulation annealing treatment on the multi-channel filter to form an inter-channel steady-state coupling structure and establishing a spectral drift compensation parameter includes: Anneal a multipass filter using a temperature pulse sequence, record the change in the phase coupling strength between the main reference channel and the observation channels at different temperature points, and obtain a temperature response curve; Perform pulsed annealing at the temperature points where the phase coupling strength shows a sudden change according to the temperature response curve, record the attenuation coefficient and recovery time of the coupling strength, and form a steady-state coupling structure between the channels; Apply a temperature perturbation to the steady-state coupling structure between the channels, obtain the response timing relationship of each observation channel, and record the temperature-stress correlation data; Analyze the spectral drift law according to the temperature-stress correlation data, and establish a drift compensation parameter table for each observation channel.

[0014] The second aspect of the present invention provides a multipass filter, which is prepared by using the preparation method of the multipass filter in the above embodiment.

[0015] The preparation method of the multipass filter proposed by the present invention. First, select the main reference channel, perform difference frequency modulation excitation using a narrow linewidth laser, and obtain the optical transmission coupling data between the main reference channel and the observation channels. Through the difference frequency modulation of the narrow linewidth laser, phonon resonance can be excited in the main reference channel, form a phonon propagation channel, establish a directional energy transmission path from the main reference channel to the observation channels, thereby obtaining the light intensity attenuation coefficient and phase delay parameters, making the physical correlation between the channels measurable.

[0016] Based on the obtained optical transmission coupling data, perform periodic perturbation detection on the observation channels to obtain the spectral drift correlation data between the channels. Specifically, by applying an angular perturbation wave, obtain the relationship between the transmitted light intensity and the angle, determine the standing wave frequency, establish a frequency response network, and then obtain the phase correlation data between the channels and the timing relationship of spectral drift. This active perturbation detection method can characterize the co-variation law of each passband under perturbation.

[0017] According to the spectral drift correlation data, modulate the deposition power and gas pressure during the film deposition process to form a crosstalk suppression layer between the channels. By analyzing the drift frequency difference between adjacent observation channels to divide the deposition cycle, set a reverse power modulation curve, form a gas pressure fluctuation gradient, and finally construct a specific refractive index structure and stress distribution in the film to weaken the unnecessary crosstalk between the channels.

[0018] On the basis of the crosstalk suppression layer, form a three-layer dielectric layer structure with gradually increasing optical thickness, and set a periodically varying coupling control layer between the dielectric layer structures of different channels. Obtain the optical path difference compensation parameters by calculating the spectral drift compensation amount, deposit the three layers of dielectrics in sequence, and deposit the coupling control layer according to the thickness change sequence to achieve precise compensation for the drift between the passbands.

[0019] Finally, perform temperature modulation annealing on the multi-pass filter to form a steady-state coupling structure between channels and establish spectral drift compensation parameters. Through temperature pulse sequence annealing, precise annealing is carried out at the phase coupling strength mutation point, the attenuation coefficient and recovery time of the coupling strength are recorded, so that the stress distribution in the multi-pass filter reaches a steady-state balance. At the same time, a spectral drift compensation parameter table is established to provide a basis for practical applications.

[0020] This preparation method comprehensively considers the physical coupling relationship between passbands, actively measures, regulates and compensates the spectral drift between passbands during the preparation process, fundamentally solves the problem in the prior art that it is impossible to simultaneously capture and quantify the coupling relationship between passbands, effectively avoids the problem of misfocusing of the entire array in the micro multi-spectral system, and improves the accuracy and stability of the multi-pass filter in practical applications. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0022] Figure 1 It is a schematic diagram of an embodiment of the preparation method of the multi-pass filter in the embodiment of the present invention.

[0023] The realization of the purpose, functional features and advantages of the present invention will be further described with reference to the embodiments and the drawings. Detailed Embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0026] In addition, the descriptions involving "first", "second", etc. in the present invention are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, "and / or" throughout the text includes three scenarios. Taking A and / or B as an example, it includes the technical solution of A, the technical solution of B, and the technical solution where A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, which must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] An embodiment of the present application provides a method for preparing a multi-pass filter. Figure 1 It is a flowchart of a method for preparing a multi-pass filter provided by an embodiment of the present application. In this embodiment, the method includes: Please refer to Figure 1 , select a main reference channel, and use a narrow-linewidth laser to perform difference-frequency modulation excitation on the main reference channel to obtain optical transmission coupling data between the main reference channel and the observation channel; In an embodiment of the present invention, the selecting a main reference channel, using a narrow-linewidth laser to perform difference-frequency modulation excitation on the main reference channel, and obtaining optical transmission coupling data between the main reference channel and the observation channel includes: Select a central channel as the main reference channel based on the correlation analysis of spectral transmittance and central wavelength, and determine the channels having a common film layer with the main reference channel as the observation channels; Modulate the narrow-linewidth laser into multiple difference-frequency waveforms, and form a one-to-one correspondence between the frequency distribution of the difference-frequency waveforms and the phonon resonance frequencies of the observation channels; Excite phonon resonance in the main reference channel according to the difference-frequency waveforms, and record the frequency response characteristics of the phonon resonance; Adjust the frequency response characteristics of the phonon resonance to form a phonon propagation channel in the common film layer of the main reference channel and the observation channels, and obtain the phonon propagation intensity distribution; Based on the phonon propagation intensity distribution, control the directionality of the phonon propagation channel, and establish a directional energy transmission path from the main reference channel to the observation channels; Record the light intensity attenuation coefficient and phase delay parameters in the directional energy transmission path respectively to form optical transmission coupling data.

[0028] The following specifically describes the steps involved in the above embodiments: When selecting the main reference channel, first measure the spectral transmittance of all channels of the multi-pass filter using a spectral analyzer to obtain the transmittance curves of each channel. Spectral transmittance refers to the ratio of the intensity of light with a specific wavelength passing through the filter to the intensity of the incident light. Then calculate the correlation coefficient between the central wavelength of each channel and the central wavelengths of other channels, where the central wavelength refers to the wavelength corresponding to the maximum value of the transmittance curve. Correlation analysis refers to calculating the strength of the mutual relationship between the central wavelengths of each channel through statistical methods, and selecting the channel with the largest sum of correlation coefficients as the central channel, that is, the main reference channel. Examine the film layer structure of the filter using an optical microscope combined with cross-section analysis technology, and determine the channels that share at least one film layer structure with the main reference channel as the observation channels. The shared film layer refers to the thin film layer that is used simultaneously by two or more channels in the multi-pass filter structure. The purpose of selecting the main reference channel is to establish a central reference system to uniformly characterize the spectral drift behavior of other observation channels through this reference system.

[0029] When modulating a narrow-linewidth laser into multiple difference-frequency waveforms, use an acousto-optic modulator to perform difference-frequency modulation on the narrow-linewidth laser (linewidth < 0.1nm). A narrow-linewidth laser refers to a laser with an extremely narrow spectral linewidth, usually generated by a single-frequency laser. A difference-frequency waveform refers to a new signal waveform whose frequency is equal to the difference between the frequencies of two signals with different frequencies when they interact. In the modulation process, first measure the phonon resonance frequency of each observation channel. The phonon resonance frequency refers to the characteristic frequency of lattice vibration in the material, usually in the range of 0.1 - 10 THz, which can be obtained by measuring with a Raman spectrometer. Then pass the narrow-linewidth laser through the acousto-optic modulator to generate multiple difference-frequency waveforms, and set the difference-frequency interval to the phonon resonance frequency of the observation channel to form a one-to-one correspondence. This precisely corresponding difference-frequency modulation method can achieve selective excitation of specific observation channels.

[0030] When exciting phonon resonance according to the difference-frequency waveform, precisely focus the modulated laser on the main reference channel, and control the laser power density within the range of 0.5 - 5 mW / μm 2 . Phonon resonance refers to the phenomenon that when the external excitation frequency matches the intrinsic frequency of phonons in the material, the phonon amplitude increases significantly. Use a high-speed photodetector combined with a lock-in amplifier to record the frequency response characteristics of phonon resonance. The frequency response characteristics refer to the response ability of the system to input signals with different frequencies, including resonance frequency, response intensity, full width at half maximum, and phase information. The full width at half maximum refers to the width of the response curve at half of the maximum value, which is an important parameter to measure the sharpness of resonance. During the recording process, use a frequency-sweeping technique to scan within the preset frequency range with a step of 10 MHz to draw a complete frequency response curve. This precise frequency response measurement provides basic data for the formation of subsequent phonon propagation channels.

[0031] When adjusting the frequency response characteristics of phonon resonance, a piezoelectric ceramic micro-displacement platform is used to apply a directional stress to the main reference channel, and the stress direction is consistent with the distribution direction of the common film layer. The phonon propagation channel refers to the path along which phonon energy preferentially propagates in the multi-layer film system. By adjusting the magnitude and direction of the stress, the frequency response characteristics of phonon resonance are changed, which are specifically manifested as the displacement of the resonance peak and the change of the peak shape. A near-field scanning optical microscope combined with phonon imaging technology is used to obtain the phonon propagation intensity distribution map. The phonon propagation intensity distribution refers to the distribution of phonon energy in space, usually represented by a two-dimensional or three-dimensional image. This distribution map uses pseudo-color to represent the phonon propagation intensity at different positions, with red indicating high intensity and blue indicating low intensity. Such fine adjustment and high-resolution imaging technology make the formation process of the phonon propagation channel controllable and visible.

[0032] When controlling the directionality of the phonon propagation channel, first, the phonon propagation intensity distribution data is processed by two-dimensional Fourier transform to obtain the phonon wave vector distribution map. The phonon wave vector is a physical quantity that characterizes the propagation direction and momentum of phonons, and the wave vector distribution data refers to the distribution of phonon wave vectors in different directions. According to the wave vector distribution characteristics, a liquid crystal spatial light modulator is used to precisely modulate the polarization state of the incident laser. The polarization state modulation refers to the purposeful control of the electric field vibration direction of the light wave. The modulated light field forms a specific phonon wavefront pattern at the film interface of the main reference channel. The phonon wavefront refers to the spatial surface composed of phonon waves with the same phase at the same moment. By controlling the tilt direction and curvature of the wavefront pattern, the directional control of the phonon propagation channel is achieved. The directional energy transmission path refers to the specific propagation channel for energy to travel from the source point to the target point, which has directionality and selectivity. Such precise directional control significantly improves the energy transmission efficiency.

[0033] When recording the parameters in the directional energy transmission path, an optical power meter and a phase-sensitive detection system are used to measure the light intensity attenuation coefficient and the phase delay parameter in the energy transmission path respectively. The light intensity attenuation coefficient refers to the degree of light intensity attenuation along the transmission direction, with the unit of dB / mm. The phase delay parameter refers to the degree of phase change of the light wave during transmission, usually expressed in radians or as a ratio relative to the wavelength. The optical transmission coupling data refers to the data set that characterizes the energy and phase transfer characteristics between two optical channels. For each directional energy transmission path, the parameter changes at at least 5 different incident angles are recorded to form a complete optical transmission coupling data set. These precisely measured optical transmission coupling data are the key parameters that characterize the physical correlation between the passbands in the multi-pass filter, providing a data basis for subsequent periodic perturbation detection and spectral drift correlation analysis.

[0034] In an embodiment of the present invention, controlling the directionality of the phonon propagation channel based on the phonon propagation intensity distribution and establishing a directional energy transmission path from the main reference channel to the observation channel includes: Perform a Fourier transform on the phonon propagation intensity distribution according to the spatial distribution characteristics to obtain phonon wavevector distribution data; Perform polarization state modulation on the phonon propagation channels according to the phonon wavevector distribution data to obtain a phonon polarization direction map; Perform phonon wavefront modulation on the film interfaces of the main reference channels according to the phonon polarization direction map and the phonon wavevector distribution data to form phonon transmission channels; Use the phonon transmission channels to couple the energies of the main reference channel and the observation channel to establish a directional energy transmission path.

[0035] The following specifically describes the steps involved in the above embodiments: When performing a Fourier transform on the phonon propagation intensity distribution according to the spatial distribution characteristics, first use a high-resolution phonon imaging system to obtain two-dimensional spatial distribution data of the phonon propagation intensity, with the spatial resolution controlled within 10 nm. The phonon propagation intensity distribution refers to the spatial distribution of phonon energy in the multi-pass filter film layer, represented by the image data measured by a near-field scanning optical microscope. Input the obtained two-dimensional distribution data into a digital signal processor for two-dimensional fast Fourier transform (FFT) operation. The Fourier transform is a mathematical processing method that converts a spatial-domain signal into a wavevector-domain signal. During the Fourier transform process, first perform Hanning window function processing on the original data to reduce edge effects, and then perform a 2048×2048-point FFT operation to finally obtain the phonon wavevector distribution data. The phonon wavevector distribution data refers to the distribution of phonon wavevector components in different directions and magnitudes, characterizing the directionality and momentum distribution of phonon propagation. For example, when phonons propagate strongly in a specific direction, the wavevector components in the corresponding direction will appear as bright spots or high-value regions in the distribution map. This method of obtaining the wavevector distribution through Fourier transform can reveal the essential characteristics of phonon propagation at the microscopic level and provide a data basis for subsequent precise control of phonon propagation.

[0036] When modulating the polarization state of the phonon propagation channel based on the phonon wave vector distribution data, a spatial light modulator (SLM) is used in combination with a polarization control system to modulate the polarization state of the probe beam. The polarization state refers to the state of the vibration direction of the optical wave electric field vector, which can be linear polarization, circular polarization or elliptical polarization. First, the phonon wave vector distribution data is processed by a computer to extract the wave vector components and their intensities in the main propagation direction, and a wave vector-polarization mapping relationship table is constructed. According to this mapping relationship, different phase delays are applied to each pixel unit of the SLM, and the phase delay range is 0-2π with an accuracy of π / 100, so that the probe beam has a polarization state matching the phonon wave vector distribution at different positions. The modulated polarization distribution is recorded by a polarization imaging system to form a phonon polarization direction map. The phonon polarization direction map refers to the distribution of the phonon vibration direction in space, usually represented by a pseudo-color image, and different colors represent different polarization directions. For example, in the TiO2 / SiO2 multilayer film structure of a multi-pass filter, through this polarization state modulation, the polarization direction of the probe light can be precisely matched with the vibration direction of the transverse acoustic phonon mode, thereby enhancing the phonon-photon interaction in a specific direction. This precise polarization state modulation technology significantly improves the direction selectivity of the phonon propagation channel and reduces the energy loss in non-target directions.

[0037] When performing phonon wavefront modulation on the film layer interface of the main reference channel based on the phonon polarization direction map and the phonon wave vector distribution data, a piezoelectric nano-displacement array is used to apply an accurate mechanical stress distribution to the film layer interface of the main reference channel. The phonon wavefront refers to the equiphase surface formed by phonon waves with the same phase at the same moment, and phonon wavefront modulation refers to changing the phase distribution of phonon waves by external means. First, the phonon polarization direction map and the wave vector distribution data are converted into a stress distribution pattern, and the magnitude and direction of the stress required at each position are calculated. Then, through a 64×64 array of piezoelectric nano-displacement devices, a spatially distributed stress field is generated on the film layer interface of the main reference channel, and the stress range is controlled at 10-50 MPa with a displacement accuracy of 0.1 nm. This stress distribution causes spatial changes in the acoustic properties of the film layer interface, forming a phonon transmission channel. The phonon transmission channel refers to the path along which phonon energy preferentially propagates in the multilayer film system, which has the characteristics of low scattering loss and high transmission efficiency. For example, between the main reference channel and a specific observation channel, a phonon transmission channel with a width of 200-500 nm can be formed, and the phonon propagation loss in this channel is more than 30% lower than that in the surrounding area. This phonon transmission channel formation technology based on precise wavefront modulation solves the problem that it is difficult to control the phonon propagation direction in traditional methods and provides a physical way for precise energy transmission between channels in multi-pass filters.

[0038] When using the phonon transmission channel to perform energy coupling between the main reference channel and the observation channel, phonon energy with a specific frequency is injected into the main reference channel through a pulsed laser, and the phonon energy propagates directionally to the target observation channel through the previously formed phonon transmission channel. Energy coupling refers to the directional transfer process of energy from one system to another system. The laser pulse width is set to 100 fs - 1 ps, the repetition frequency is 10 - 100 MHz, and the energy density is controlled within 0.1 - 1 J / cm 2 range. When the injected phonon energy propagates in the transmission channel, a time-resolved Brillouin scattering spectrometer is used to monitor the energy transmission process, and the energy transmission efficiency, propagation speed, and directivity parameters are recorded. After the phonon energy is successfully transmitted to the target observation channel, the response signal of the observation channel is measured through an optical detection system, thereby establishing a directional energy transmission path from the main reference channel to the observation channel. The directional energy transmission path refers to a specific propagation path of energy from the source point to the target point, with clear directivity and selectivity. For example, for the main reference channel in the 500 - 550 nm band and the observation channel in the 600 - 650 nm band, a directional transmission path with an energy transmission efficiency of more than 85% can be established, and the transmission time delay is less than 100 ps. This directional energy coupling technology based on the phonon transmission channel realizes efficient energy transfer between different channels in the multi-channel filter, laying a foundation for accurately measuring the optical transmission coupling characteristics between channels.

[0039] Please continue to refer to Figure 1 , and perform periodic perturbation detection on the observation channel according to the optical transmission coupling data to obtain spectral drift correlation data between channels; In an embodiment of the present invention, the performing periodic perturbation detection on the observation channel according to the optical transmission coupling data to obtain spectral drift correlation data between channels includes: Construct the spectral response spatial distribution of the observation channel according to the light intensity attenuation coefficient and phase delay parameter of the optical transmission coupling data; Based on the spectral response spatial distribution, apply an angular perturbation wave with a periodic change in the observation channel to obtain the relationship between the transmitted light intensity and the angle; According to the relationship between the transmitted light intensity and the angle, modulate the frequency of the angular perturbation wave to the frequency corresponding to the trough of the transmitted light intensity wave, and record the light intensity response curve; According to the light intensity response curve, determine the standing wave frequency of the angular perturbation wave in the observation channel, and establish the frequency response network of the observation channel; Modulate the optical field phase between different observation channels through the standing wave frequency in the frequency response network to obtain the phase correlation data between channels; Determine the timing relationship of spectral drift between the observation channels according to the phase correlation data to form spectral drift correlation data between channels.

[0040] The following is a specific description of the steps involved in the above embodiments: When constructing the spectral response spatial distribution of the observation channel based on the light intensity attenuation coefficient and phase delay parameter of the optically transmitted coupled data, first import the obtained light intensity attenuation coefficient and phase delay parameter into the data processing system. The light intensity attenuation coefficient refers to the degree of attenuation of the light intensity during transmission, with the unit of dB / mm; the phase delay parameter refers to the phase change generated by the light wave during transmission, with the unit of rad / mm. Use a three-dimensional imaging spectrometer to perform a spatial scan on the observation channel, set the scan step size to 5μm, and the scan range covers the entire observation channel area (usually 0.5mm×0.5mm). At the same time, record the spectral transmittance of each spatial point to form an initial data set. Then combine the light intensity attenuation coefficient and phase delay parameter with the initial data set, and calculate the response value of each spatial point at different wavelengths through a convolution algorithm to obtain the spectral response spatial distribution of the observation channel. The spectral response spatial distribution refers to the response intensity distribution of different spatial positions in the observation channel to light of different wavelengths, which is represented by a three-dimensional color image, where the X and Y axes represent spatial coordinates, the Z axis represents the response intensity, and the color represents the wavelength. For example, for an observation channel with a central wavelength of 550nm, the response intensity distribution map of each spatial point in the wavelength range of 500 - 600nm can be obtained. This method of constructing the spectral response spatial distribution based on measured parameters can accurately reflect the optical characteristics of the observation channel and provide spatial targeting information for subsequent precise perturbation.

[0041] When applying a periodically varying angular perturbation wave in the observation channel based on the spectral response spatial distribution, use a piezoelectric angle adjustment platform to modulate the angle of the filter. The angular perturbation wave refers to an incident angle modulation signal that periodically varies at a certain frequency. First, determine the most sensitive region based on the spectral response spatial distribution, that is, the channel region with the strongest response to angle changes, usually select the region with the largest response intensity gradient. Then use a piezoelectric angle adjustment platform to apply a periodic angular change to the filter, control the angular change range within ±2 degrees, with a resolution of 0.001 degrees, and gradually increase the frequency from 0.1Hz to 100Hz, with a step size of 0.1Hz. At the same time, use a high-sensitivity photodetector to monitor the change in transmitted light intensity in real time. The response time of the photodetector is less than 10μs to ensure that fast-changing light signals can be accurately captured. Record the transmitted light intensity values at different angles and plot the curve of the transmitted light intensity changing with the angle. For example, for an observation channel with a central wavelength of 550nm, when the incident angle changes from 0 degrees to 0.5 degrees, the transmitted light intensity may drop from 100% to 80%, and when the angle continues to increase, the transmitted light intensity will show a periodic change. This method of obtaining the relationship between light intensity changes through angular perturbation can effectively detect the angle-sensitive characteristics of the multi-pass filter and reveal the coupling mechanism between channels.

[0042] According to the relationship between the transmitted light intensity and the angle, when the frequency of the angular perturbation wave is modulated to the frequency corresponding to the trough of the transmitted light intensity wave, first analyze the transmitted light intensity - angle curve to determine the trough position. The trough of the transmitted light intensity refers to the local minimum point in the transmitted light intensity curve. Use data analysis software to perform peak detection on the transmitted light intensity - angle curve and accurately mark the angle values at all trough positions. Then, based on these trough angle values, calculate the corresponding angular perturbation frequencies. Set the driving frequency of the piezoelectric angle - adjusting platform to the frequency corresponding to the trough angle, with the frequency accuracy controlled within 0.01 Hz. Use a digital oscilloscope to record the change in light intensity response at this frequency, set the sampling rate to 10 kHz, and the recording time to no less than 60 seconds to ensure capturing the complete response characteristics. Plot the angular perturbation frequency - light intensity response curve to form the light intensity response curve. The light intensity response curve refers to the relationship curve of the light intensity changing with the angular perturbation frequency, reflecting the response characteristics of the filter to angular perturbations of different frequencies. For example, when the angular perturbation frequency is 10.5 Hz, the transmitted light intensity in a certain observation channel may show obvious periodic attenuation, indicating the presence of resonance at this frequency. This method of accurately aligning the angular perturbation frequency with the trough of the transmitted light intensity can effectively excite the characteristic response of the observation channel and provide accurate data for determining the standing - wave frequency.

[0043] When determining the standing - wave frequency of the angular perturbation wave in the observation channel based on the light intensity response curve, use a spectrum analyzer to perform spectrum analysis on the light intensity response curve. The standing - wave frequency refers to the characteristic frequency at which the angular perturbation wave forms a stable standing wave in the observation channel. First, perform a fast Fourier transform (FFT) on the light intensity response curve to convert the time - domain signal into a frequency - domain signal, with the number of FFT points set to 8192 points to obtain sufficient frequency resolution. Identify the resonance peaks from the spectrum, that is, the frequency points where the energy is concentrated, and these frequency points are the potential standing - wave frequencies. Then, verify whether these frequency points are the true standing - wave frequencies through a phase - detection method, that is, check whether the phase relationship at these frequency points satisfies the standing - wave condition. Sort the verified standing - wave frequency points according to the energy magnitude and select the top 3 - 5 standing - wave frequencies as the characteristic frequencies of the observation channel. Use these characteristic frequencies to construct the frequency - response network of the observation channel. The frequency - response network refers to the topological structure that describes the response relationship of the observation channel to different frequencies, usually represented in the form of a directed graph, where the nodes represent the channels and the edges represent the frequency - response relationships. For example, for a certain observation channel, the standing - wave frequencies may be determined to be 10.5 Hz, 15.3 Hz, and 22.7 Hz, and these frequencies constitute the frequency - characteristic fingerprint of this channel. This method of establishing the frequency - response network based on the standing - wave frequency can accurately characterize the dynamic characteristics of the observation channel from the frequency domain perspective and provide a frequency basis for subsequent inter - channel phase modulation.

[0044] When modulating the optical field phase between different observation channels by the standing wave frequency in the frequency response network, a spatial light modulator (SLM) is used to perform spatial phase modulation on the incident optical field. The optical field phase refers to the phase distribution state of the light wave in space. First, the standing wave frequency information of each determined observation channel is input into the SLM control system. For the standing wave frequency of each observation channel, a corresponding phase modulation pattern is designed, with the phase modulation depth controlled within the range of 0 - 2π, and the spatial resolution reaching 10μm × 10μm. The designed phase modulation pattern is loaded onto the SLM to modulate the incident optical field. An interference imaging system is used to monitor the phase changes of each observation channel after modulation in real time, with the phase measurement accuracy reaching λ / 20. The phase differences between each observation channel at different standing wave frequencies are recorded to construct the phase correlation matrix between channels. The phase correlation data refers to the data set describing the phase relationship between different observation channels, including the phase difference and its variation law with the standing wave frequency. For example, for two adjacent observation channels, there may be a phase difference of π / 4 at a standing wave frequency of 10.5Hz, and the phase difference may become π / 2 at a standing wave frequency of 15.3Hz. This method of optical field phase modulation based on the standing wave frequency can accurately control and characterize the phase relationship between observation channels, providing a phase basis for subsequent analysis of spectral drift.

[0045] When determining the timing relationship of spectral drift between observation channels according to the phase correlation data, a spectral dynamic analysis system is used to perform a perturbation response test on the multi-channel filter. Spectral drift refers to the shift of the central wavelength or bandwidth of the filter passband due to changes in external factors; the timing relationship refers to the sequence and causal relationship of spectral drift in different channels over time. First, a small thermal perturbation is applied to the multi-channel filter, with the temperature change range controlled within ±0.5℃ and the heating / cooling rate being 0.1℃ / minute. A high-precision spectrometer is used to monitor the spectral changes of each observation channel in real time, with the wavelength resolution reaching 0.01nm and the time resolution being 100ms. Combining the previously obtained phase correlation data, the time delay and amplitude relationship of spectral drift in each observation channel are calculated, with the time delay accuracy reaching 1ms. A spectral drift timing diagram between observation channels is plotted to show the sequence and amplitude relationship of drift in different channels, forming the spectral drift correlation data between channels. The spectral drift correlation data refers to the data set describing the mutual relationship of spectral drift between different observation channels, including information such as drift amplitude, direction, and timing. For example, under thermal perturbation, the channel with a central wavelength of 550nm may first undergo a 0.2nm redshift, and then the channel with a central wavelength of 600nm undergoes a 0.15nm redshift with a 20ms delay. This method of spectral drift timing analysis based on phase correlation can accurately reveal the spectral drift coupling mechanism between channels in the multi-channel filter, providing a key basis for subsequent film deposition design.

[0046] In an embodiment of the present invention, determining the standing wave frequency of the angular perturbation wave in the observation channel according to the light intensity response curve and establishing the frequency response network of the observation channel includes: Performing wavelet transform decomposition on the light intensity response curve to obtain frequency component data; Calculating the standing wave node positions in the observation channel according to the frequency component data to form a standing wave distribution map; Performing phase compensation calculation according to the standing wave distribution map and the frequency component data to obtain the standing wave frequency parameter; Using the standing wave frequency parameter to perform frequency response modulation on the observation channel to establish a frequency response network.

[0047] The following specifically describes the steps involved in the above embodiment: When performing wavelet transform decomposition on the light intensity response curve, a digital signal processor is used to process the previously obtained light intensity response curve data. Wavelet transform is a time-frequency analysis method that can provide the local characteristics of a signal simultaneously in the time domain and the frequency domain. First, the light intensity response curve data is segmented according to a window length of 2048 points, and the window overlap rate is set to 50% to ensure the continuity of the analysis. Then, the db4 (Daubechies-4) wavelet basis function is selected for five-layer wavelet decomposition. The db4 wavelet basis function has good local characteristics and smoothness, which is suitable for analyzing the subtle changes in the light intensity signal. Wavelet decomposition divides the signal into approximation coefficients (low-frequency part) and detail coefficients (high-frequency part), and each layer of decomposition obtains a set of frequency components. The decomposition results of all levels are comprehensively sorted out to form frequency component data. The frequency component data refers to the amplitude and phase information of different frequency components in the light intensity response curve, which is represented in the form of a data matrix. For example, for the observation channel with a central wavelength of 550 nm, after wavelet transform decomposition, the main frequency components may be distributed in three intervals of 8 - 12 Hz, 15 - 18 Hz, and 22 - 25 Hz. This frequency decomposition method based on wavelet transform has better time-frequency localization characteristics compared with the traditional Fourier transform, and can accurately capture the non-stationary and transient characteristics in the light intensity response curve, providing high-quality frequency component information for the subsequent calculation of the standing wave node positions.

[0048] When calculating the positions of standing-wave nodes in the observation channel based on frequency-component data, a spatial phase mapping technique is used to finely scan the observation channel. A standing-wave node refers to the position point in a standing wave where the amplitude is zero, that is, the spatial point where the phase changes abruptly or the energy is minimal. First, a phase-sensitive optical coherence tomography scanner is used to perform a two-dimensional scan of the observation channel with a step size of 5 μm, and the scanning range covers the entire observation channel area (usually 0.5 mm × 0.5 mm). For each main frequency component obtained by wavelet transform, the phase distribution and energy distribution at this frequency are recorded during the scanning process. According to the spatial coordinates of the phase mutation points and energy minimum points, the positions of the standing-wave nodes at this frequency are determined. The information on the positions of the standing-wave nodes of all main frequency components is integrated to form a standing-wave distribution map of the observation channel. The standing-wave distribution map refers to the spatial distribution of standing-wave nodes with different frequencies in the observation channel, usually represented by a two-dimensional color image, and different colors represent standing-wave nodes with different frequencies. For example, in an observation channel with a central wavelength of 550 nm, the standing-wave nodes with a frequency of 10 Hz may show an annular distribution, while the standing-wave nodes with a frequency of 15 Hz may show a radial distribution. This method of calculating standing-wave nodes based on frequency components can accurately reveal the spatial characteristics of the energy distribution in the observation channel, providing an intuitive basis for understanding the light field-structure interaction in a multi-pass filter.

[0049] When performing phase compensation calculations based on the standing-wave distribution map and frequency-component data, a digital phase synthesizer is used to precisely regulate the phase distribution in the observation channel. Phase compensation refers to the process of eliminating unwanted phase deviations in the system by adding specific phase delays. First, according to the spatial distribution characteristics of the standing-wave nodes with different frequencies in the standing-wave distribution map, the phase differences between regions are calculated. For regions with discontinuous or jumping phases, corresponding phase compensation functions are designed, with a phase compensation range of 0 - 2π and a compensation accuracy of π / 100. Then, the phase compensation functions are combined with the frequency-component data to calculate the precise compensation values required for each frequency component. After phase compensation, the coherence and energy distribution of each frequency component are recalculated, and the characteristic parameters of each frequency component are extracted, including the central frequency, bandwidth, Q value (quality factor), and frequency stability, to form standing-wave frequency parameters. The standing-wave frequency parameters refer to the key parameter set describing the standing-wave characteristics in the observation channel, including frequency values, intensity coefficients, and phase characteristics. For example, for a certain observation channel, the standing-wave frequency parameters may include a central frequency of 10.2 Hz, a bandwidth of 0.5 Hz, a Q value of 20, and a frequency stability of ±0.02 Hz. This precise phase compensation calculation not only improves the accuracy of the standing-wave frequency parameters but also eliminates the phase errors caused by optical path differences and structural non-uniformities in the system, ensuring the accuracy of subsequent frequency response modulation.

[0050] When using the standing - wave frequency parameter to modulate the frequency response of the observation channel, an adaptive frequency control system is adopted to dynamically regulate the light - field distribution in the observation channel. Frequency - response modulation refers to changing the frequency characteristics of the system to exhibit specific frequency - response behaviors. First, the standing - wave frequency parameter is loaded into the frequency control system, and the modulation target and accuracy requirements are set. A piezoelectric phase modulator is used to spatially modulate the phase of the incident light field, and the modulation region precisely corresponds to the spatial range of the observation channel, with the modulation depth controlled within the range of 0 - 2π. For each standing - wave frequency parameter, a corresponding modulation signal is generated, and the frequency accuracy of the modulation signal is controlled within ±0.01 Hz. By continuously adjusting the phase and amplitude of the modulation signal, the observation channel forms a stable frequency - response characteristic at each standing - wave frequency. The response characteristics at different standing - wave frequencies are connected to form a complete frequency - response curve, and a frequency - response correlation network between observation channels, namely the frequency - response network, is established. The frequency - response network refers to the topological structure that describes the collective frequency - response characteristics of the observation channels, characterizing the response relationships between channels at different frequencies. For example, in a system composed of three adjacent observation channels, the frequency - response network can show that the coupling strength between channel 1 and channel 2 is 0.8 at the standing - wave frequency of 10.2 Hz, while the coupling strength between channel 2 and channel 3 is 0.5. This frequency - response modulation technology based on the standing - wave frequency parameter realizes precise control of the frequency characteristics of the observation channel, making the dynamic response characteristics of the multi - pass filter measurable and adjustable.

[0051] Please continue to refer to Figure 1 , according to the spectral - drift correlation data, modulate the deposition power and air pressure during the film deposition process to form a crosstalk suppression layer between channels; In an embodiment of the present invention, the modulating the deposition power and air pressure during the film deposition process according to the spectral - drift correlation data to form a crosstalk suppression layer between channels includes: Analyze the drift - frequency difference between adjacent observation channels in the spectral - drift correlation data, and divide the film deposition process into multiple deposition cycles according to the magnitude of the frequency difference; Set different deposition - power modulation frequencies for each deposition cycle to form a power - modulation curve opposite to the drift frequency of the observation channel, and record the deposition - power compensation data; According to the deposition - power compensation data, calculate the air - pressure modulation amplitude for each deposition cycle, form an air - pressure fluctuation gradient between adjacent deposition cycles, and obtain the air - pressure modulation curve; According to the air - pressure modulation curve, form a periodic structure with alternating refractive indices during the film deposition process, and measure the refractive - index change amplitude; Divide the stress transition region between adjacent observation channels according to the refractive - index change amplitude, and record the stress - distribution gradient; The stress distribution gradient is hierarchically modulated according to the drift frequency difference to form an inter-channel crosstalk suppression layer in the film layer.

[0052] The following specifically describes the steps involved in the above embodiments: When analyzing the drift frequency difference between adjacent observation channels in the spectral drift correlation data, a high-precision spectral data processing system is used to process the previously obtained spectral drift correlation data. The drift frequency difference refers to the difference value between the frequency characteristics of spectral drifts of adjacent observation channels, with the unit of Hz. First, the spectral drift correlation data is imported into the data processing system, and the spectral drift frequency characteristics of each observation channel are extracted. The Fourier analysis method is used to calculate the drift main frequency of each observation channel, and the frequency resolution is set to 0.01 Hz. Then, the drift frequency difference between adjacent observation channels is calculated to form a difference distribution map. According to the magnitude of the frequency difference in the difference distribution map, a threshold segmentation point is set, and the difference range is divided into 3-5 intervals. Each interval corresponds to a deposition cycle in the film layer deposition process. The deposition cycle refers to the time period with relatively consistent deposition parameters during the film layer deposition process. For example, when the drift frequency difference between adjacent channels is 0-0.5 Hz, it is divided into the first deposition cycle, 0.5-1.5 Hz is the second deposition cycle, 1.5-3.0 Hz is the third deposition cycle, and greater than 3.0 Hz is the fourth deposition cycle. This method of dividing the deposition cycle based on the drift frequency difference takes into account the differences in the drift characteristics of different channels in the multi-channel filter, enabling precise regulation of subsequent deposition processes for different frequency difference intervals.

[0053] When setting different deposition power modulation frequencies for each deposition cycle, the deposition power is dynamically modulated using the precision power controller of the magnetron sputtering deposition system. The deposition power modulation frequency refers to the frequency at which the deposition power changes periodically during the film deposition process, with the unit of Hz. First, for each deposition cycle, analyze the drift frequency characteristics of the observation channel within that cycle. According to the value and direction of the drift frequency, design a power modulation frequency that is opposite to it, that is, when the observation channel shows a positive drift frequency, set a reverse power modulation frequency. The magnitude of the power modulation frequency is proportional to the drift frequency, and the proportionality factor is set between 1.2 - 1.5. Use a digital power modulator to generate a power waveform that meets the requirements, with the modulation depth controlled within the range of ±10%, and the base power set to 200 - 300W. Record the actual power value, modulation frequency, and power response curve during the power modulation process in real time to form deposition power compensation data. Deposition power compensation data refers to the set of power regulation data used to offset spectral drift during the film deposition process. For example, for the second deposition cycle (the drift frequency difference is 0.5 - 1.5Hz), if the observation channel shows a positive drift frequency of 1.0Hz, then set the power modulation frequency to -1.2Hz (the negative sign indicates reverse), and the power fluctuation range is 270W ± 27W. This power modulation method opposite to the drift frequency can actively suppress the inherent spectral drift trend of the multi-pass filter during the deposition process and reduce the mutual influence between channels from the source.

[0054] When calculating the air pressure modulation amplitude for each deposition cycle based on the deposition power compensation data, a high-precision air pressure control system is used to dynamically adjust the air pressure in the deposition chamber. The air pressure modulation amplitude refers to the range of periodic changes in the chamber air pressure during the thin film deposition process, with the unit of Pa. First, according to the power change curve in the deposition power compensation data, calculate the gradient and fluctuation characteristics of the power change within each deposition cycle. Adopt the air pressure-power response conversion algorithm to convert the power change curve into the corresponding air pressure modulation requirement, and set the conversion coefficient to 0.5 - 0.8 Pa / W. To enhance the difference between adjacent deposition cycles, an additional air pressure gradient is applied at the cycle boundary to form an air pressure fluctuation gradient. The air pressure fluctuation gradient refers to the rate difference of air pressure changes between adjacent deposition cycles, with the unit of Pa / min. The gradient magnitude is set to 5 - 8% of the average air pressure within the cycle, and the direction is the same as the power modulation direction. The intake air volume is adjusted in real time through a precision mass flow controller to make the chamber air pressure change according to the set curve, and record the air pressure change curve of the entire deposition process to form an air pressure modulation curve. For example, for the deposition process with a base air pressure of 0.5 Pa, the air pressure modulation amplitude of the first deposition cycle is ±0.02 Pa, and that of the second deposition cycle is ±0.04 Pa, forming an air pressure fluctuation gradient of 0.025 Pa / min at the junction of the two cycles. This precise air pressure modulation method combined with power modulation realizes the multi-parameter collaborative control of thin film growth kinetics during the film deposition process, significantly improving the structural accuracy and stability of the multi-pass filter.

[0055] When forming a periodic structure with alternating refractive indices during the film deposition process according to the gas pressure modulation curve, an in-situ optical monitoring system is used to monitor the film growth process in real-time. The periodic structure with alternating refractive indices refers to a film layer structure in a multi-layer film system where the refractive index changes periodically according to a specific pattern. First, the gas pressure change during the deposition process is controlled according to the gas pressure modulation curve, while monitoring the growth rate and optical properties of the film. The change in gas pressure causes changes in the energy distribution and oxidation degree of sputtered particles, which in turn affects the density and stoichiometry of the deposited film, and ultimately forms a periodic change in refractive index. A single-wavelength monitor and a spectroscopic ellipsometer are used to measure the refractive index change of the film in real-time. The measurement wavelength is set to 550 nm, and the sampling frequency is 10 Hz. By controlling the deposition parameters, high and low refractive index materials (such as TiO2 and SiO2) are alternately deposited according to the designed periodic structure, and the thickness of each film layer is controlled within the range of 50 - 150 nm, with a thickness accuracy of ±1 nm. The change in the refractive index of the film during the entire deposition process is measured to obtain the amplitude of the refractive index change. The amplitude of the refractive index change refers to the maximum change in the refractive index of the film layer in the periodic structure, which is dimensionless. For example, for a TiO2 / SiO2 multi-layer film system, a periodic structure with refractive indices alternating between 1.46 - 2.35 can be formed, and the amplitude of the refractive index change is 0.89. This technique for forming a periodic refractive index structure based on gas pressure modulation not only achieves optical isolation between channels in a multi-pass filter but also enhances the selective transmission characteristics of the filter through the interference effect of the periodic structure.

[0056] When dividing the stress transition region between adjacent observation channels according to the amplitude of refractive index change, a high-resolution stress analysis system is used to characterize the stress distribution of the thin film. The stress transition region refers to the region where the stress state gradually changes between adjacent observation channels in the multi-pass filter. First, according to the refractive index change amplitude data, the internal stress distribution of the thin film is calculated by the pressure-stress response algorithm, and the algorithm conversion accuracy is set to ±5 MPa. The stress distribution is closely related to the refractive index change. Regions with large refractive index change amplitudes usually correspond to regions with large stress change gradients. The Raman spectroscopy stress measurement technique is used to perform a surface scan on the multi-pass filter, with a spatial resolution of 2 μm and a stress measurement accuracy of ±10 MPa. According to the measurement results, the contour lines of the stress distribution are determined, and 3-5 stress transition regions are divided between adjacent observation channels. The stress change gradient in each region is in the range of 10-50 MPa / mm. Record the boundary positions, widths, and stress change rates of each stress transition region to form the stress distribution gradient. The stress distribution gradient refers to the rate of change of stress with respect to the spatial coordinate, with the unit of MPa / mm. For example, for adjacent observation channels with central wavelengths of 550 nm and 600 nm, three stress transition regions are divided between them. The stress gradient in the inner region is 15 MPa / mm, the middle region is 30 MPa / mm, and the outer region is 20 MPa / mm. This stress zoning method based on refractive index change transforms the stress distribution in the multi-pass filter from a random and disordered state to a controllable and ordered state, providing a structural basis for subsequent crosstalk suppression.

[0057] When performing hierarchical modulation of the stress distribution gradient according to the drift frequency difference, a precision ion beam assisted deposition system is used to finally modulate the film structure of the multi-pass filter. Hierarchical modulation refers to the modulation process of applying different parameters to film layers at different depths. First, establish a correspondence table between the stress distribution gradient and the drift frequency difference, and the correspondence coefficient is set to 8-12 MPa·mm -1 ·Hz -1 . According to this correspondence, design a hierarchical modulation scheme: regions with large drift frequency differences are modulated using high-energy ion beams (300-500 eV), medium-difference regions are modulated using medium-energy ion beams (150-300 eV), and low-difference regions are modulated using low-energy ion beams (50-150 eV). The ion beam density is controlled at 0.1-0.5 mA / cm 2Within a certain range, the incident angle is set to 30 - 60 degrees. By precisely controlling the energy, density, and incident angle of the ion beam, a specific stress modulation structure is formed in different stress transition regions, and finally a crosstalk suppression layer between channels is formed in the film layer of the multi-pass filter. The crosstalk suppression layer between channels refers to a special functional film layer structure that can weaken the signal interference between adjacent observation channels. The thickness of this crosstalk suppression layer is usually 100 - 300 nm, with a specific stress distribution and refractive index gradient, which can effectively block the energy coupling between channels. For example, the crosstalk suppression layer formed between the observation channels with central wavelengths of 550 nm and 600 nm can attenuate the crosstalk signal between channels by more than 20 dB. This hierarchical modulation technology based on the stress distribution gradient and the difference in drift frequencies realizes the effective suppression of crosstalk between channels in the multi-pass filter, significantly improving the channel isolation and spectral stability of the filter.

[0058] In one embodiment of the present invention, the step of dividing the stress transition region between adjacent observation channels according to the amplitude of the refractive index change and recording the stress distribution gradient includes: Performing stress field decomposition on the amplitude of the refractive index change to obtain the principal stress component data; Calculating the stress transfer coefficient between adjacent observation channels according to the principal stress component data to form a stress transfer matrix; Calculating the boundary stress of the stress transition region according to the stress transfer matrix and the principal stress component data to obtain stress transition parameters; Using the stress transition parameters to calculate the stress distribution between adjacent observation channels and recording the stress distribution gradient.

[0059] The following specifically describes the steps involved in the above embodiments: When decomposing the amplitude of refractive index change into stress fields, a photoelastic stress analysis system is used to finely measure the multi-pass filter. Stress field decomposition refers to the process of decomposing a complex stress distribution state into the main stress components in different directions. First, a high-resolution photoelastic polarization microscope is used to scan the filter sample, with a spatial resolution set to 1 μm and an angular resolution of 1 degree, and the scanning range covering adjacent observation channels and their transition regions (usually 1 mm × 1 mm). At each scanning point, the phase difference between the optical path difference and the reference light is recorded, and the phase difference accuracy reaches λ / 100. The phase difference data is correlated with the amplitude of refractive index change obtained above to establish the refractive index-stress correspondence. Then, the principal stress decomposition algorithm is used to decompose the stress field, decomposing the complex stress state into three components: the principal stress in the X direction, the principal stress in the Y direction, and the shear stress in the XY direction. The principal stress component data refers to the data set representing the magnitudes of the main stresses in each direction in the multi-pass filter, with the unit of MPa. For example, for a filter with a TiO2 / SiO2 multi-layer structure, the range of the principal stress value in the X direction is from +50 to -30 MPa, the range of the principal stress value in the Y direction is from +40 to -20 MPa, and the range of the shear stress value in the XY direction is ±15 MPa. This stress field decomposition method based on refractive index change can accurately reveal the stress distribution state in the multi-pass filter, providing accurate basic data for subsequent stress transfer analysis.

[0060] When calculating the stress transfer coefficient between adjacent observation channels based on the principal stress component data, a stress propagation analysis system is used to characterize the stress transfer characteristics. The stress transfer coefficient refers to the attenuation or amplification ratio when stress transfers from one region to another, dimensionless. First, a small mechanical vibration excitation is applied to the boundary region between adjacent observation channels, with the vibration frequency set to 10 - 100 Hz and the amplitude controlled within the range of 10 - 50 nm. A laser Doppler vibrometer is used to measure the vibration transfer characteristics, recording the vibration amplitude change and phase delay from one observation channel to the adjacent observation channel. Combining the principal stress component data obtained above, the stress transfer coefficient is calculated through the stress-vibration response analysis algorithm. For each pair of adjacent observation channels in the multi-pass filter, the stress transfer coefficients in the X direction, Y direction, and XY direction are calculated to form a stress transfer matrix. The stress transfer matrix refers to a two-dimensional array describing the stress transfer relationship between each observation channel in the multi-pass filter, and the matrix elements are the stress transfer coefficients in each direction. For example, for three adjacent observation channels with central wavelengths of 500 nm, 550 nm, and 600 nm respectively, the stress transfer matrix between them may contain nine elements, representing the stress transfer characteristics in three directions between the three channels. This method for calculating the stress transfer coefficient based on vibration analysis can quantitatively characterize the stress transfer characteristics in the multi-pass filter, providing key parameters for the optimal design of the stress transition region.

[0061] When calculating the boundary stress of the stress transition region based on the stress transfer matrix and the principal stress component data, an exact simulation is carried out using boundary element analysis software. The boundary stress refers to the stress state at the boundary of the stress transition region, with the unit of MPa. First, a geometric model of the stress transition region is constructed, and the model accuracy is controlled at the micron level, including the complete boundaries of adjacent observation channels. The stress transfer matrix and the principal stress component data are input into the analysis software, and the material parameters (such as Young's modulus, Poisson's ratio, and density, etc.) are set. The value of Young's modulus is set in the range of 50 - 200 GPa according to different materials. The finite element method is used to calculate the stress distribution at the boundary of the stress transition region, and the calculation accuracy is set to ±1 MPa. Parameters such as the stress gradient, stress concentration factor, and stress decay length at the boundary are extracted to form stress transition parameters. The stress transition parameters refer to a set of characteristic parameters that describe how stress changes in the transition region, including the stress gradient (MPa / μm), stress concentration factor (dimensionless), and stress decay length (μm), etc. For example, for a filter with a TiO2 / SiO2 multilayer film structure, the stress gradient in the stress transition region is 0.2 - 0.5 MPa / μm, the stress concentration factor is 1.5 - 2.5, and the stress decay length is 50 - 100 μm. This exact boundary stress calculation method enables the design of the stress transition region in the multi-pass filter to change from empirical adjustment to quantitative optimization, significantly improving the structural stability of the filter.

[0062] When calculating the stress distribution between adjacent observation channels using the stress transition parameters, the stress field reconstruction technology is adopted to accurately calculate the stress distribution in the entire transition region. The stress distribution refers to the distribution state of stress in space, usually represented in the form of a tensor field. First, the stress transition parameters are input into the stress field reconstruction system, and the calculation grid size is set to 1μm×1μm, covering the entire transition region between the observation channels. Based on the boundary stress conditions obtained previously, the stress diffusion equation is used for iterative calculation, with the iterative accuracy set to 0.1 MPa and the number of iterations controlled within 100 - 500 times. The stress tensor values of each grid point in the transition region are calculated to generate a complete stress distribution map. Then, the rate of change of stress along the transition region is calculated, that is, the stress distribution gradient. The stress distribution gradient refers to the rate at which the stress value changes with the spatial position, with the unit of MPa / μm. The stress distribution gradient values at key positions are recorded to form a stress distribution gradient data set. For example, for the transition region between two adjacent observation channels, the stress distribution gradient in the X direction may be 0.3 MPa / μm, in the Y direction is 0.2 MPa / μm, and in the XY direction is 0.1 MPa / μm. This stress distribution calculation method based on the stress transition parameters realizes the accurate characterization and control of the stress distribution in the multi-pass filter, provides a stress distribution basis for the precise formation of the crosstalk suppression layer, and ultimately achieves the technical effect of improving the channel isolation and spectral stability of the multi-pass filter.

[0063] Please continue to refer to Figure 1 and, according to the spectral drift correlation data, form a three-layer dielectric layer structure with gradually increasing optical thickness on the crosstalk suppression layer, and set a periodically varying coupling control layer between the dielectric layer structures of different channels; In an embodiment of the present invention, the forming a three-layer dielectric layer structure with gradually increasing optical thickness on the crosstalk suppression layer and setting a periodically varying coupling control layer between the dielectric layer structures of different channels according to the spectral drift correlation data includes: Calculate the spectral drift compensation amount between observation channels according to the phase correlation data in the spectral drift correlation data to obtain the optical path difference compensation parameter; Based on the optical path difference compensation parameter, deposit a first dielectric layer, a second dielectric layer, and a third dielectric layer on the crosstalk suppression layer in sequence, and record the thickness gradient data of the three layers of dielectrics; Analyze the thickness gradient data of the three layers of dielectrics to obtain the optical path difference change curve between the dielectric layers, and record the optical path difference distribution data; Calculate the periodic modulation parameter between adjacent observation channels according to the optical path difference distribution data to form a periodic thickness change sequence; Deposit a coupling control layer between the three-layer dielectric structures of adjacent observation channels according to the thickness change sequence.

[0064] The following is a specific description of the steps involved in the above embodiment: When calculating the spectral drift compensation amount between observation channels according to the phase correlation data in the spectral drift correlation data, a phase-spectral conversion system is used to accurately process the data. The spectral drift compensation amount refers to the wavelength or optical path adjustment amount required to offset the spectral drift, with the unit of nm. First, extract the phase correlation data from the previously obtained spectral drift correlation data. The phase correlation data is a data set describing the phase relationship between different observation channels. Use a digital phase processor to analyze the phase correlation data, calculate the phase difference value and phase drift trend between each pair of adjacent observation channels. Convert the phase difference into the corresponding wavelength drift amount through a phase-wavelength conversion algorithm, and the conversion coefficient is set to 0.01 - 0.05 nm / degree (phase angle). Calculate the required optical path difference compensation value according to the wavelength drift amount. The optical path difference is equal to the product of the physical thickness and the refractive index. The optical path difference compensation parameter refers to the optical path difference value that needs to be adjusted to achieve spectral drift compensation, with the unit of nm. For example, for adjacent observation channels with central wavelengths of 550 nm and 600 nm, if a 5-degree phase difference is measured between them, corresponding to a 0.2-nm wavelength drift, the required optical path difference compensation parameter is 10 nm. This method of calculating the optical path difference compensation based on phase correlation realizes an accurate mapping from the phase domain to the spectral domain, providing a quantitative design basis for subsequent dielectric layer deposition.

[0065] When depositing three dielectric layers successively on the crosstalk suppression layer based on the optical path difference compensation parameters, a high-precision ion beam assisted deposition system is used for precise control. First, a three-layer dielectric structure scheme is designed according to the optical path difference compensation parameters. The first dielectric layer is made of a low refractive index material (such as SiO2, with a refractive index of about 1.46), the second dielectric layer is made of a medium refractive index material (such as Al2O3, with a refractive index of about 1.76), and the third dielectric layer is made of a high refractive index material (such as TiO2, with a refractive index of about 2.35). On the surface of the crosstalk suppression layer formed above, the ion beam cleaning technology is first used to remove possible surface contamination. The cleaning ion energy is controlled at 200 - 300 eV, and the scanning rate is 2 - 5 mm / s. Then, the high-precision ion beam assisted deposition system is started. The energy of the assisted ion beam is set at 50 - 150 eV, the deposition rate is controlled at 0.1 - 0.3 nm / s, and the chamber vacuum is maintained below 1×10 -6 Pa. The three dielectric materials are deposited successively, and the thickness of each layer is precisely controlled according to the design scheme, with the thickness monitoring accuracy reaching ±0.5 nm. At the same time, an in-situ ellipsometer is used to monitor the thickness change of each dielectric layer in real time, record the thickness change from the center to the edge of the observation channel, and form the thickness gradient data of the three dielectric layers. The thickness gradient data refers to the data set describing the spatial change rate of the film thickness, with the unit of nm / mm. For example, the thickness gradient of the first dielectric layer from the center to the edge is 2 nm / mm, that of the second dielectric layer is 3 nm / mm, and that of the third dielectric layer is 4 nm / mm. This design of the three-layer dielectric structure with gradually increasing optical thickness forms a gradient-changing optical path difference distribution, which can effectively compensate for the spectral drift between observation channels.

[0066] When analyzing the thickness gradient data of the three-layer medium, an optical thin film analysis system is used for precise characterization. First, a high-resolution optical profiler is used to perform a three-dimensional scan of the deposited three-layer medium structure, with the spatial resolution set to 0.1 μm and the scan range covering adjacent observation channels and their transition regions. According to the scan data, the thickness distribution map of each layer of the medium is drawn to form an intuitive spatial thickness gradient expression. Then, the product of the physical thickness and the refractive index of the material at each point, that is, the optical path difference, is calculated to generate the spatial distribution map of the optical path difference. The surface fitting is performed on the optical path difference distribution data to obtain the optical path difference change curve. The optical path difference change curve refers to the function relationship curve of the optical path difference changing along the spatial coordinate. Along the connection direction between the observation channels, the key characteristic points of the optical path difference distribution are extracted, including extreme points, inflection points, and zero points, etc., and the coordinates and optical path difference values of these characteristic points are recorded to form the optical path difference distribution data. The optical path difference distribution data refers to the set of key data points describing the spatial distribution characteristics of the optical path difference. For example, for the region between two adjacent observation channels, the optical path difference distribution data contains three extreme points (the maximum value is 300 nm, the second maximum value is 250 nm, and the minimum value is 150 nm) and two inflection points (slope change points). This optical path difference analysis method based on the thickness gradient realizes the precise characterization of the optical properties of the multi-layer medium structure and provides a data basis for subsequent periodic modulation.

[0067] When calculating the periodic modulation parameters between adjacent observation channels according to the optical path difference distribution data, an optical periodic structure optimization system is used for design. The periodic modulation parameters refer to the set of parameters describing the characteristics of the periodic structure, including the spatial period (period length), modulation depth (amplitude), and phase, etc. First, the spatial variation characteristics in the optical path difference distribution data are analyzed to extract the spatial frequency components. The Fourier transform is performed on the optical path difference distribution data using spatial spectrum analysis software to obtain the main spatial frequency components, and the frequency resolution is set to 0.01 μm. -1 According to the spatial frequency characteristics, a periodic modulation scheme is designed: the spatial period is set to the reciprocal of the main frequency in the optical path difference distribution (usually 1 - 10 μm), the modulation depth is set to 30 - 50% of the amplitude of the optical path difference change, and the phase is set to match the position of the optical path difference extreme point. Combining these parameters, a complete thickness change sequence is generated. The thickness change sequence refers to the numerical sequence of the periodic change of the thin film thickness along the connection direction between the observation channels. For example, for a design with a spatial period of 5 μm and a modulation depth of 20 nm, the thickness values in the thickness change sequence may fluctuate ±10 nm above and below the reference thickness (such as 100 nm), showing a sine or sine-like periodic change. This periodic thickness design method based on the optical path difference distribution realizes the collaborative optimization of spectral drift compensation and the optical properties of the periodic structure, and significantly improves the spectral stability of the multi-pass filter.

[0068] When depositing the coupling regulation layer between the three-layer dielectric structures of adjacent observation channels according to the thickness change sequence, an ultra-precision film-making system is used for precise deposition. The coupling regulation layer refers to a special functional film layer that can regulate the optical coupling characteristics between adjacent observation channels. First, according to the previously designed thickness change sequence, a suitable material combination is selected. Usually, a dual-material structure with alternating refractive indices is adopted, such as SiO2 / TiO2 or SiO2 / Ta2O5. Using precisely controlled electron beam evaporation or ion beam sputtering technology, deposition is carried out in the area between the three-layer dielectric structures of adjacent observation channels. During the deposition process, a computer-controlled dynamic mask technology is used to achieve a periodically varying thickness distribution. The mask position accuracy is controlled within ±1μm, and the thickness control accuracy reaches ±0.2nm. The mask moving speed and the deposition rate are coordinated and regulated to form a periodically varying thickness that meets the design requirements. The total thickness of the coupling regulation layer is controlled within the range of 50 - 200nm, and the number of periods is set to 5 - 20 according to the design requirements. For example, for the transition region between adjacent observation channels with a spatial period of 5μm and a total length of 100μm, a coupling regulation layer with 20 periods can be designed. Each period includes 5nm thick SiO2 and 3nm thick TiO2, and the total thickness is 160nm. This periodically varying coupling regulation layer structure realizes precise coupling control of the light field between observation channels through Bragg reflection and optical interference effects, effectively compensates for spectral drift under different working conditions, and significantly improves the spectral stability and channel isolation of the multi-pass filter.

[0069] Please continue to refer to Figure 1 , perform temperature-modulated annealing treatment on the multi-pass filter to form a steady-state coupling structure between channels and establish spectral drift compensation parameters.

[0070] In one embodiment of the present invention, the performing temperature-modulated annealing treatment on the multi-pass filter to form a steady-state coupling structure between channels and establish spectral drift compensation parameters includes: Using a temperature pulse sequence to perform annealing treatment on the multi-pass filter, record the change in the phase coupling intensity between the main reference channel and the observation channels at different temperature points, and obtain a temperature response curve; According to the temperature response curve, perform pulsed annealing at the temperature points where the phase coupling intensity shows a sudden change, record the attenuation coefficient and recovery time of the coupling intensity, and form a steady-state coupling structure between channels; Apply a temperature perturbation to the steady-state coupling structure between channels, obtain the response timing relationship of each observation channel, and record the temperature-stress correlation data; Analyze the spectral drift law according to the temperature-stress correlation data, and establish a drift compensation parameter table for each observation channel.

[0071] The following specifically describes the steps involved in the above embodiment: When annealing a multi-pass filter using a temperature pulse sequence, a precision temperature control system is used to perform heat treatment on the filter. The temperature pulse sequence refers to a sequence of temperature waveforms that change according to a preset pattern within a specific time. First, place the multi-pass filter on a high-precision temperature control platform with a temperature control accuracy of ±0.1°C and a temperature range set from room temperature to 300°C. Design the parameters of the temperature pulse sequence: the base temperature is set at 25°C, the peak temperature of the pulse starts from 50°C and gradually increases to 250°C in steps of 10°C, the duration of each pulse is 60 seconds, the pulse interval time is 180 seconds, the heating rate is controlled at 2°C / second, and the cooling rate is controlled at 1°C / second. During the application of each temperature pulse, use a phase-sensitive interference system to monitor the phase relationship between the main reference channel and each observation channel in real time. The phase coupling strength refers to the degree of optical field phase correlation between the main reference channel and the observation channel, quantified as the phase correlation coefficient, with a value range of 0 - 1. Record the phase coupling strength values at each temperature point and plot the curve of the phase coupling strength versus temperature, which is the temperature response curve. For example, for the main reference channel with a central wavelength of 550nm and the observation channel with a central wavelength of 600nm, the phase coupling strength may remain between 0.8 - 0.9 in the range of 25 - 100°C, drop sharply to 0.3 - 0.4 in the range of 100 - 120°C, and then stabilize at 0.5 - 0.6 in the range of 120 - 200°C. This annealing method based on the temperature pulse sequence can systematically detect the temperature-dependent characteristics of the phase coupling strength between channels in the multi-pass filter, providing temperature window information for subsequent precise annealing.

[0072] When performing pulsed annealing at the temperature point where the phase coupling strength shows a sudden change according to the temperature response curve, a rapid thermal processing system is used to precisely heat-treat the multi-pass filter. The sudden change point of the phase coupling strength refers to the temperature point at which the phase coupling strength changes sharply in the temperature response curve, usually manifested as a significant change in the curve slope. First, analyze the temperature response curve and use the derivative analysis method to determine several temperature points with the largest change in the curve slope, that is, the sudden change points of the phase coupling strength. Usually, the temperature point where the phase coupling strength changes from high to low is selected as the main processing temperature point. Place the multi-pass filter in a rapid thermal processing furnace and set precise temperature control parameters: the target temperature is set to the sudden change point temperature, the temperature control accuracy is ±0.5°C, the heating rate is 10 - 20°C / second, the holding time is 30 - 90 seconds, and the cooling rate is 5 - 10°C / second. During the annealing process, use an in-situ optical monitoring system to record the change of the phase coupling strength in real time, including the attenuation coefficient and the recovery time. The attenuation coefficient refers to the rate of attenuation of the phase coupling strength, with the unit of 1 / second; the recovery time refers to the time required for the phase coupling strength to recover from attenuation to stability, with the unit of second. For example, for a multi-pass filter with a sudden change point temperature of 110°C, the attenuation coefficient may be 0.05 / second and the recovery time is 20 seconds. Through this precise pulsed annealing treatment, the internal stress in the multi-pass filter is released, and the molecular structure reaches a more stable arrangement state, forming a steady-state coupling structure between channels. The steady-state coupling structure refers to the structural form in which the phase coupling relationship between channels reaches a relatively stable state after annealing treatment. This precise annealing method based on the sudden change point of the phase coupling strength realizes the effective release of the internal stress in the multi-pass filter, while maintaining the necessary optical coupling relationship between channels, and significantly improves the thermal stability and spectral stability of the filter.

[0073] When a temperature perturbation is applied to the steady-state coupling structure between channels, a dynamic temperature change test is performed on the multi-pass filter using a temperature gradient test system. Temperature perturbation refers to a small-amplitude temperature change applied purposefully. First, design a temperature perturbation scheme: the base temperature is set to 25 °C, the perturbation amplitude is set to ±5 °C, the perturbation frequency is set to 0.01 - 0.1 Hz, and the perturbation waveforms include sine waves, triangular waves, square waves, etc. The test duration for each waveform is 30 minutes. Place the annealed multi-pass filter on the temperature gradient test platform and apply the designed temperature perturbation. Use a high-speed spectral analyzer to simultaneously monitor the spectral changes in the main reference channel and each observation channel. The spectral sampling rate is set to 10 Hz, and the wavelength resolution reaches 0.01 nm. Record the real-time data of the spectral parameters (such as central wavelength, bandwidth, and transmittance) of each channel changing with temperature, extract the time-series characteristics such as time delay, amplitude ratio, and phase difference of the response of each channel, and form response time-series relationship data. At the same time, use a photoelastic stress analysis system to monitor the stress changes in the multi-pass filter and record the correlation data between the stress state and temperature changes, that is, temperature-stress correlation data. Temperature-stress correlation data refers to a data set that describes the quantitative relationship between temperature changes and stress changes, including information such as temperature coefficients, stress response delays, and stress distribution changes. For example, for a certain multi-pass filter, when the temperature increases by 1 °C, the compressive stress in the central region may increase by 0.5 MPa, while the tensile stress in the edge region may increase by 0.3 MPa, and there is a response time difference of 2 - 5 seconds between regions. This dynamic response test method based on temperature perturbation systematically reveals the stress change law and spectral drift characteristics of the multi-pass filter under actual working temperature fluctuations, providing a direct basis for subsequent compensation parameter calculation.

[0074] When analyzing the spectral drift law based on the temperature-stress correlation data, use a data mining system to systematically analyze the test results. First, perform time synchronization processing on the temperature-stress correlation data and the spectral change data to establish a time-series correlation database. Use a multivariate correlation analysis method to calculate the correlation coefficient matrix among temperature changes, stress changes, and spectral drift, and determine the main influencing factors and influence paths. Then, use a regression analysis method to fit the quantitative relationship of temperature-stress-spectral drift, and control the equation fitting accuracy within R 2> 0.95. Based on the fitting equation, calculate the spectral drift characteristics of each observation channel under different temperature change patterns, including drift direction, drift amplitude, drift rate, etc. The spectral drift law refers to the functional relationship between the spectral parameters of each channel in the multi-pass filter with temperature or stress changes. For the drift law of each observation channel, design corresponding compensation parameters, including temperature compensation coefficient (unit: nm / °C), stress compensation coefficient (unit: nm / MPa), and time compensation parameter (unit: nm / second), etc. Organize these compensation parameters into a drift compensation parameter table, which refers to a data table in which the system records the spectral drift characteristics of each observation channel and its compensation parameters. For example, for an observation channel with a central wavelength of 550 nm, its temperature compensation coefficient may be 0.015 nm / °C, the stress compensation coefficient is 0.02 nm / MPa, and the time compensation parameter is 0.005 nm / second. This spectral drift analysis method based on temperature-stress correlation data not only reveals the internal mechanism of spectral drift in multi-pass filters but also provides accurate compensation parameters, enabling the filter to achieve high-precision spectral stability through active compensation technology in the actual working environment, effectively solving the "whole-column defocusing" problem (i.e., multiple channels simultaneously undergo related drifts, but due to the lack of a corresponding drift coupling prediction mechanism, it becomes difficult to trace and compensate for the deterioration of system performance) that occurs in traditional multi-pass filters under temperature fluctuations.

[0075] The present invention also proposes a multi-pass filter, which is prepared by using the preparation method of the multi-pass filter in any of the above embodiments. Therefore, it has the beneficial effects brought by any of the above embodiments, and will not be elaborated here one by one.

[0076] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A preparation method of a multi-pass filter, characterized in that, Including: Selecting a main reference channel, and using a narrow-linewidth laser to perform difference-frequency modulation excitation on the main reference channel to obtain optical transmission coupling data between the main reference channel and an observation channel; According to the optical transmission coupling data, performing periodic perturbation detection on the observation channel to obtain spectral drift correlation data between channels; According to the spectral drift correlation data, modulating the deposition power and air pressure during the film deposition process to form a crosstalk suppression layer between channels; According to the spectral drift correlation data, forming a three-layer dielectric layer structure with gradually increasing optical thickness on the crosstalk suppression layer, and arranging a periodically varying coupling control layer between the dielectric layer structures of different channels; Performing temperature modulation annealing treatment on the multi-channel filter to form a steady-state coupling structure between channels and establishing spectral drift compensation parameters.

2. The preparation method of the multi-pass filter according to claim 1, characterized in that, The step of selecting a main reference channel, and using a narrow-linewidth laser to perform difference-frequency modulation excitation on the main reference channel to obtain optical transmission coupling data between the main reference channel and an observation channel includes: Selecting a central channel as the main reference channel based on the correlation analysis of spectral transmittance and central wavelength, and determining the channels having a common film layer with the main reference channel as observation channels; Modulating the narrow-linewidth laser into multiple difference-frequency waveforms, and establishing a one-to-one correspondence between the frequency distribution of the difference-frequency waveforms and the phonon resonance frequency of the observation channel; Exciting phonon resonance in the main reference channel according to the difference-frequency waveforms and recording the frequency response characteristics of the phonon resonance; Adjusting the frequency response characteristics of the phonon resonance to form a phonon propagation channel in the common film layer of the main reference channel and the observation channel, and obtaining the phonon propagation intensity distribution; Based on the phonon propagation intensity distribution, controlling the directionality of the phonon propagation channel to establish a directional energy transmission path from the main reference channel to the observation channel; Respectively recording the light intensity attenuation coefficient and phase delay parameter in the directional energy transmission path to form optical transmission coupling data.

3. The preparation method of the multi-pass filter according to claim 2, characterized in that The step of based on the phonon propagation intensity distribution, controlling the directionality of the phonon propagation channel to establish a directional energy transmission path from the main reference channel to the observation channel includes: Performing Fourier transform on the phonon propagation intensity distribution according to the spatial distribution characteristics to obtain phonon wave vector distribution data; Performing polarization state modulation on the phonon propagation channel according to the phonon wave vector distribution data to obtain a phonon polarization direction map; Performing phonon wavefront modulation on the film layer interface of the main reference channel according to the phonon polarization direction map and the phonon wave vector distribution data to form a phonon transmission channel; Using the phonon transmission channel to perform energy coupling between the main reference channel and the observation channel to establish a directional energy transmission path.

4. The preparation method of the multi-pass filter according to claim 1, wherein, The step of according to the optical transmission coupling data, performing periodic perturbation detection on the observation channel to obtain spectral drift correlation data between channels includes: Constructing a spatial distribution of the spectral response of the observation channel according to the light intensity attenuation coefficient and phase delay parameter of the optical transmission coupling data; Based on the spatial distribution of the spectral response, applying a periodically varying angular perturbation wave in the observation channel to obtain the relationship between the transmitted light intensity and the angle; According to the variation relationship of the transmitted light intensity with the angle, the frequency of the angular perturbation wave is modulated to the frequency corresponding to the trough of the transmitted light intensity wave, and the light intensity response curve is recorded; According to the light intensity response curve, the standing wave frequency of the angular perturbation wave in the observation channel is determined, and the frequency response network of the observation channel is established; The optical field phase between different observation channels is modulated by the standing wave frequency in the frequency response network to obtain the phase correlation data between the channels; According to the phase correlation data, the timing relationship of the spectral drift between the observation channels is determined to form the spectral drift correlation data between the channels.

5. The preparation method of the multi-pass filter according to claim 4, characterized in that, The determining the standing wave frequency of the angular perturbation wave in the observation channel according to the light intensity response curve and establishing the frequency response network of the observation channel includes: Performing wavelet transform decomposition on the light intensity response curve to obtain frequency component data; Calculating the standing wave node positions in the observation channel according to the frequency component data to form a standing wave distribution map; Performing phase compensation calculation according to the standing wave distribution map and the frequency component data to obtain the standing wave frequency parameter; Using the standing wave frequency parameter to perform frequency response modulation on the observation channel to establish a frequency response network.

6. The preparation method of the multi-pass filter according to claim 1, characterized in that, The modulating the deposition power and the air pressure during the film deposition process according to the spectral drift correlation data to form a crosstalk suppression layer between the channels includes: Analyzing the drift frequency difference between adjacent observation channels in the spectral drift correlation data, and dividing the film deposition process into multiple deposition cycles according to the magnitude of the frequency difference; Setting different deposition power modulation frequencies for each deposition cycle to form a power modulation curve opposite to the drift frequency of the observation channel, and recording the deposition power compensation data; Calculating the air pressure modulation amplitude of each deposition cycle according to the deposition power compensation data, forming an air pressure fluctuation gradient between adjacent deposition cycles, and obtaining an air pressure modulation curve; Forming a periodic structure with alternating refractive indices during the film deposition process according to the air pressure modulation curve, and measuring the refractive index change amplitude; Dividing the stress transition region between adjacent observation channels according to the refractive index change amplitude, and recording the stress distribution gradient; Performing hierarchical modulation on the stress distribution gradient according to the drift frequency difference to form a crosstalk suppression layer between the channels in the film.

7. The preparation method of the multi-pass filter according to claim 6, characterized in that The dividing the stress transition region between adjacent observation channels according to the refractive index change amplitude and recording the stress distribution gradient includes: Performing stress field decomposition on the refractive index change amplitude to obtain the principal stress component data; Calculating the stress transfer coefficient between adjacent observation channels according to the principal stress component data to form a stress transfer matrix; Performing boundary stress calculation on the stress transition region according to the stress transfer matrix and the principal stress component data to obtain the stress transition parameter; Performing stress distribution calculation between adjacent observation channels by using the stress transition parameter, and recording the stress distribution gradient.

8. The preparation method of the multi-pass filter according to claim 1, characterized in that, The forming a three-layer dielectric layer structure with gradually increasing optical thickness on the crosstalk suppression layer and setting a periodically varying coupling control layer between the dielectric layer structures of different channels according to the spectral drift correlation data includes: Calculating the spectral drift compensation amount between the observation channels according to the phase correlation data in the spectral drift correlation data to obtain the optical path difference compensation parameter; Based on the optical path difference compensation parameters, deposit a first dielectric layer, a second dielectric layer, and a third dielectric layer on the crosstalk suppression layer in sequence, and record the thickness gradient data of the three dielectric layers; Analyze the thickness gradient data of the three dielectric layers to obtain the optical path difference change curve between the dielectric layers, and record the optical path difference distribution data; Calculate the periodic modulation parameters between adjacent observation channels according to the optical path difference distribution data to form a periodic thickness change sequence; Deposit a coupling regulation layer between the three dielectric layer structures of adjacent observation channels according to the thickness change sequence.

9. The preparation method of the multi-pass filter according to claim 1, characterized in that, Perform temperature modulation annealing on the multi-pass filter to form a steady-state coupling structure between channels, and establish spectral drift compensation parameters, including: Use a temperature pulse sequence to anneal the multi-pass filter, and record the change in the phase coupling strength between the main reference channel and the observation channels at different temperature points to obtain a temperature response curve; Perform pulsed annealing at the temperature points where the phase coupling strength changes abruptly according to the temperature response curve, and record the attenuation coefficient and recovery time of the coupling strength to form a steady-state coupling structure between channels; Apply a temperature perturbation to the steady-state coupling structure between channels, obtain the response timing relationship of each observation channel, and record the temperature-stress correlation data; Analyze the spectral drift law according to the temperature-stress correlation data, and establish a drift compensation parameter table for each observation channel.

10. A multi-pass filter, characterized in that, The multi-pass filter is prepared by using the preparation method of the multi-pass filter according to any one of claims 1 to 9.

Images