Method and system for detecting interface state space distribution of centrosymmetric material
By using the phase ionogram iterative optimization method and constructing phase ionograms with Zernike polynomials, the problem of detecting electrical parameters at the micro-nano scale of material interfaces using SHG technology was solved, achieving high-resolution and high-sensitivity detection of the spatial distribution of interface states, and improving signal quality and characterization capabilities.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF MICROELECTRONICS CHINESE ACAD OF SCI LTD
- Filing Date
- 2025-12-04
- Publication Date
- 2026-04-10
AI Technical Summary
Existing SHG technology has difficulty achieving micro-nano scale spatial resolution and high surface sensitivity detection of material interface electrical parameters.
The phase ionization diagram iterative optimization method is adopted. The phase ionization diagram is constructed by Zernike polynomial and its coefficient vector, the incident light is modulated, and iterative optimization is performed until the light intensity meets the convergence condition. The spatial distribution of the material interface states is determined by the target phase ionization diagram.
This method achieves high spatial resolution and high surface sensitivity detection of the spatial distribution of material interface states, improves the signal quality of SHG technology, and obtains in-situ characterization of the nonlinear optical response of materials and the microscopic physical state of the interface.
Smart Images
Figure CN121830581A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to the technical field of nonlinear optical characterization, and particularly relates to a method and system for detecting spatial distribution of interface state of centrosymmetric material. BACKGROUND
[0002] At present, as an important nonlinear optical characterization method, second harmonic generation (SHG) technology is mainly applied to the research on interface electrical properties of materials, and can effectively extract interface state density, carrier distribution, surface potential, and interface charge transfer behavior and other electrical parameters. With the deepening of the research on the interface micro-physical and chemical processes, higher requirements are put forward for the spatial resolution of the SHG technology, so as to promote the measurement of the above-mentioned electrical parameters from the macro scale to the micro-nano scale, and realize the visualization of the spatial distribution of the interface electronic state. Developing a new SHG characterization method with high surface sensitivity and high spatial resolution has become an important technical direction for deepening the understanding of interface science. SUMMARY
[0003] Embodiments of the present disclosure aim to provide a method and system for detecting spatial distribution of interface state of centrosymmetric material, to solve the problems in the prior art.
[0004] Embodiments of the present disclosure adopt the following technical solutions: a method for detecting spatial distribution of interface state of centrosymmetric material, comprising: splitting a preset laser pulse to form a reference light and an incident light; constructing a phase hologram and modulating the incident light according to the phase hologram; irradiating the interface of a sample with the modulated incident light to obtain reflected light; collecting light intensity after the reflected light and the reference light are coherent, and judging whether the light intensity satisfies a convergence condition; in the case that the light intensity does not satisfy the convergence condition, iteratively optimizing the phase hologram until the light intensity modulated according to the optimized phase hologram satisfies the convergence condition; in the case that the light intensity satisfies the convergence condition, taking the current phase hologram as a target phase hologram; and determining interface state spatial distribution information of the sample according to the target phase hologram.
[0005] In some embodiments, the phase hologram is constructed based on a Zernike polynomial and a coefficient vector thereof.
[0006] In some embodiments, the Zernike polynomial is in the form of Noll index.
[0007] In some embodiments, the iteratively optimizing the phase hologram until the light intensity modulated according to the optimized phase hologram satisfies the convergence condition comprises: setting a gain coefficient and a perturbation amplitude, and initializing an iteration number; generating a random perturbation vector according to the current iteration number wherein, is the iteration number, is the coefficient vector of the ; according to the random perturbation vector, a positive perturbation is applied to the current coefficient vector to obtain a positive perturbation eikonal; the incident light is modulated according to the positive perturbation eikonal, and a positive perturbation light intensity is determined; according to the random perturbation vector, a negative perturbation is applied to the current coefficient vector to obtain a negative perturbation eikonal; the incident light is modulated according to the negative perturbation eikonal, and a negative perturbation light intensity is determined; a light intensity gradient estimate is determined according to the positive perturbation light intensity and the negative perturbation light intensity; the current coefficient vector is updated according to the gain coefficient and the light intensity gradient estimate, and the light intensity after the coherent superposition of the reflected light and the reference light is re-acquired according to the updated coefficient vector, to determine whether the light intensity satisfies a convergence condition; in the case where the light intensity does not satisfy the convergence condition, the iteration number is incremented by 1 and a random perturbation vector is re-generated The current coefficient vector is iterated until the light intensity modulated based on the current coefficient vector satisfies a convergence condition.
[0008] In some embodiments, each element of the random perturbation vector independently obeys a Bernoulli distribution, and a positive perturbation or a negative perturbation based on the perturbation amplitude is performed with the same probability.
[0009] In some embodiments, the determination of the interface state spatial distribution information of the sample based on the target eikonal includes: obtaining a phase matrix of the target eikonal, and performing sign inversion on the phase matrix to obtain an inverted phase matrix; performing segmentation processing on the inverted phase matrix to obtain a continuous absolute phase distribution; removing optical system phase differences in the absolute phase distribution to obtain a target signal; and determining the interface state spatial distribution information of the sample based on the target signal through forward simulation and backward iteration.
[0010] In some embodiments, the determination of the interface state spatial distribution information of the sample based on the target signal through forward simulation and backward iteration includes: assuming an interface electronic state distribution , and solving Maxwell equations by a finite element method to calculate a theoretical second harmonic generated by the electronic state distribution , wherein a parameter vector is used to parameterize variables for describing the interface electronic state spatial distribution ; the interface electronic state distribution is expressed as a linear combination of a series of preset basis functions :
[0011] adjusting the parameter vector to optimize a target function with the target signal as the target :
[0012] wherein, as the target signal; a parameter vector at a minimum of the target function as the target parameter vector, and determining interface state space distribution information of the sample .
[0013] The embodiment of the present disclosure provides a detection system for interface state space distribution of a center-symmetrical material, comprising: an incident light path assembly, a reference light path assembly, an exit light path assembly, a sample stage and a processor; wherein the incident light path assembly is used for generating a preset laser pulse and splitting the preset laser pulse to form reference light and incident light, the reference light is incident into the reference light path assembly, the incident light is modulated based on a phase grating based on a spatial light modulator, and the modulated incident light is irradiated onto the surface of a sample carried on the sample stage to form reflected light; the reference light path assembly is used for modulating the reference light based on coherent matching; the exit light path assembly is used for combining the reflected light and the reference light, and collecting light intensity after the reflected light and the reference light are coherent through a photodetector; the processor is used for judging whether the light intensity satisfies a convergence condition; in the case that the light intensity does not satisfy the convergence condition, driving the spatial light modulator to iteratively optimize the phase grating until the light intensity modulated according to the optimized phase grating satisfies the convergence condition; in the case that the light intensity satisfies the convergence condition, taking the current phase grating as a target phase grating; and determining interface state space distribution information of the sample according to the target phase grating.
[0014] In some embodiments, the incident light path assembly comprises: a laser light source, a first half-wave plate, a first polarizer, a first filter, a first beam splitter, a spatial light modulator, a first optical axis adjuster, a first lens adjustment frame and a focusing lens which are sequentially arranged; the reference light path assembly comprises: a frequency doubling crystal, a second filter, a second half-wave plate, an attenuation plate, an optical path compensation device, a phase shifter and a mirror which are sequentially arranged; and the exit light path assembly comprises: a collimating mirror, a second lens adjustment frame, a second optical axis adjuster, a beam combiner, a second polarizer, a low-pass filter and a photodetector which are sequentially arranged.
[0015] In some embodiments, further comprising: an altimeter and a microscope above the sample stage; The incident light path assembly further comprises a second beam splitter arranged between the focusing lens and the sample stage, and the detection system further comprises a spot topography analyzer.
[0016] The beneficial effects of the embodiments of the present disclosure are that the dynamic compensation of the wavefront distortion of the incident light is realized based on the iteration of the phase grating, so that the reflected light formed by the reflection of the incident light after the sample interface reaches the optimal interference state with the reference light, and the optimized phase grating not only improves the signal quality of the final coherent light, but also serves as a quantitative basis for the wavefront modulation amount of the reaction sample interface, and the interface electronic state spatial distribution information of the sample can be obtained by further inversion, realizing the in-situ characterization mode of synchronously obtaining the nonlinear optical response and the interface microscopic physical state of the material. BRIEF DESCRIPTION OF DRAWINGS
[0017] In order to more clearly illustrate the technical solutions in the one or more embodiments of the present specification or the prior art, the drawings needed to be used in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present specification, and other drawings can be obtained by those skilled in the art without creative labor.
[0018] Figure 1 The flow chart of the method for detecting the interface state spatial distribution of the center-symmetric material in the first embodiment of the present disclosure is shown in Figure 2 The schematic diagram of the step of iteratively optimizing the phase grating in the first embodiment of the present disclosure is shown in Figure 3 The structural schematic diagram of the system for detecting the interface state spatial distribution of the center-symmetric material in the second embodiment of the present disclosure is shown in DETAILED DESCRIPTION
[0019] In order to make the person skilled in the art better understand the technical solutions in the one or more embodiments of the present specification, the technical solutions in the one or more embodiments of the present specification will be described clearly and completely below in combination with the drawings in the one or more embodiments of the present specification. Obviously, the described embodiments are only some embodiments of the present specification, not all embodiments. Based on the one or more embodiments of the present specification, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present document.
[0020] In order to solve the problems in the prior art, the first embodiment of the present disclosure provides a method for detecting the interface state spatial distribution of the center-symmetric material, and the flow chart is shown in Figure 1 The method mainly includes the following steps: S10, splitting the preset laser pulse to form reference light and incident light.
[0021] The preset laser pulse is an ultrashort pulse laser, and two consistent light rays are formed after light splitting. One is used as incident light to irradiate the sample interface after modulation to form a second harmonic, and the other is used as reference light to satisfy the coherence with the reflected light after reflection. In actual laser pulse processing, filtering, polarization, attenuation and other treatments of the laser should also be included, which will be described in detail in combination with the detection system of the second embodiment.
[0022] S20, constructing a phase hologram and modulating the incident light according to the phase hologram.
[0023] S30, irradiating the interface of the sample with the modulated incident light to obtain reflected light.
[0024] S40, collecting the light intensity after the coherence of the reflected light and the reference light, and judging whether the light intensity satisfies the convergence condition; in the case that the light intensity does not satisfy the convergence condition, performing step S50 to iteratively optimize the phase hologram, and re-executing S30 and S40 until the light intensity modulated according to the optimized phase hologram satisfies the convergence condition; in the case that the light intensity satisfies the convergence condition, performing step S60 to take the current phase hologram as a target phase hologram.
[0025] The spatial inhomogeneity of the interface electronic state modulates the local second-order nonlinear optical response of the material, thereby causing the wavefront of the generated second harmonic (SHG) to be distorted. In order to avoid the distortion of the interface signal wavefront output from the sample, the signal light beam enters a spatial light modulator for phase modulation based on a phase hologram and then enters a focusing mirror to focus the laser onto the sample on the sample stage to generate a second harmonic.
[0026] The phase hologram of the embodiment is used to pre-modulate the incident light to compensate for the wavefront distortion caused by the defects of the sample interface , so as to achieve the best coherence with the reference light. In this embodiment, the phase hologram is characterized and fitted based on Zernike polynomials and their coefficient vectors. Zernike polynomials are a set of complete orthogonal polynomials defined on a unit circle, which can effectively describe optical wavefront aberration. Zernike polynomials are described by two parameters: radial order and angular frequency . The standard form includes even and odd polynomials, which can be generally expressed as:
[0027] wherein, and are polar coordinates, is a normalized radial coordinate ( ), is an angular coordinate ( ); is the radial order of the polynomial (non-negative integer). It is the angular frequency (an integer, and satisfies) and (even numbers); It is the normalization coefficient, and its mathematical expression is:
[0028] in, It is the Kronecker function, specifically:
[0029] It is a radial polynomial, defined as:
[0030] It is an angular function, and for even terms we have For odd terms, .
[0031] Any continuous wavefront phase distribution All of them can be approximated by a linear combination of finite Zernike polynomials, expressed as:
[0032] in, The phase distribution to be fitted is the phase lattice diagram to be optimized in this embodiment. For the first Zernike polynomials; Corresponding to the number The coefficient vector of the Zernike polynomial, which is also the weight to be optimized; The total number of Zernike polynomial terms used determines the accuracy and complexity of wavefront fitting. In this embodiment, the Zernike polynomial uses the Noll indexing method, using the first 37 terms for wavefront fitting, corresponding to all aberration terms (36 terms in total) from radial order 0 to 7, and the 8th order spherical aberration term (the 37th term). This combination of aberration terms can effectively characterize the wavefront distortion modes encountered in most optical systems.
[0033] When constructing the phase diagram, first set the initial values of the coefficient vector of the initial Zernike polynomial. The initial phase diagram is constructed based on this, and the incident light is modulated. The modulated incident light is used to illuminate the interface of the sample to obtain reflected light. The reflected light is then combined with the reference light using a beam combiner, and the coherence of the combined light is collected as a performance indicator. The feedback is used as the convergence condition. In the actual experiment, the coherence of the combined beam is represented by the intensity of the combined beam. When the convergence condition is not met, the coefficient vector of the Zernike polynomial is iteratively optimized until it converges to a set of optimal coefficients. The optimal phasing diagram required to be loaded onto the spatial light modulator is obtained. Its expression is:
[0034] This optimal phase diagram is used to premodulate the wavefront of the incident probe light to compensate for wavefront distortion caused by defects at the sample interface, thereby achieving optimal coherence with the reference light.
[0035] In fact, the optimization of the phase ionization diagram in this embodiment is reflected in the coefficient vector of the Zernike polynomial. The iterative optimization performed can be achieved using the Stochastic Parallel Gradient Descent (SPGD) algorithm. Figure 2 This embodiment illustrates the steps for iterative optimization of the phase hysteresis diagram, which mainly include: S201, Set gain coefficient and disturbance amplitude ; S202, Initialize the number of iterations ; S203, Generate a random perturbation vector based on the current iteration number. ,in, For the first The coefficient vector of the Zernike polynomial. Specifically, each element of the random perturbation vector independently follows a Bernoulli distribution and takes the value of a positive perturbation with equal probability. or negative disturbance ; S204, based on the random perturbation vector , towards the current coefficient vector Applying a positive perturbation, we obtain Load the corresponding positive perturbation phase diagram ; S205, based on the positive perturbation phase diagram Modulate the incident light to determine the intensity of the positive perturbation light. ; S206, based on the random perturbation vector , towards the current coefficient vector Applying a negative perturbation, we obtain Load the corresponding negative perturbation phase diagram ; S207, based on the negative perturbation phase diagram Modulate the incident light to determine the intensity of the negative perturbation light. ; S208, based on the positive perturbation light intensity and negative perturbation light intensity Determine the light intensity gradient estimate ; S209, based on the gain coefficient and light intensity gradient estimation value For the current coefficient vector Perform iterative updates to obtain the updated coefficient vector. And based on the updated coefficient vector The intensity of the reflected and reference light is re-acquired and then compared to determine whether the intensity satisfies the convergence condition. If the intensity does not satisfy the convergence condition, the iteration count is incremented by 1 and a new random perturbation vector is generated. The current coefficient vector is iterated until the light intensity modulated based on the phase hysteresis diagram determined by the current coefficient vector satisfies the convergence condition. In this embodiment, the convergence condition can be the light intensity... When a preset threshold is reached, convergence is considered achieved.
[0036] S70, determine the interface state spatial distribution information of the sample based on the target phase diagram.
[0037] In this embodiment, when the SPGD algorithm iteratively finds a target phase lattice that can perfectly compensate for the distortion, this phase lattice itself contains the spatial distribution information of the interface electronic states. Based on this target phase lattice, the spatial distribution information of the interface electronic states of the sample can be inferred.
[0038] Specifically, firstly, the target phase lattice image loaded on the spatial light modulator after the SPGD algorithm converges is obtained, and then the phase matrix of the target phase lattice image is obtained. At this point, the optimal phase diagram loaded on the SLM is... This is the negative conjugate of the wavefront distortion caused by the sample. Therefore, to obtain the wavefront distortion information of the sample itself, sign inversion must be performed to obtain the inverted phase matrix. :
[0039] Subsequently, the Goldstein branching method or least squares method was used to reverse the phase matrix. Segmentation is performed to obtain a continuous absolute phase distribution. To eliminate the inherent aberrations of the optical system from the total wavefront distortion and separate the target signal generated purely from the sample interface. :
[0040] Where the first T terms (T is usually 5 to 10) fit the system aberration, which is subtracted to obtain the target signal, and finally the interface electronic state information is obtained by forward simulation and reverse iteration.
[0041] Specifically, assuming an electronic state distribution , the SHG wavefront that it should theoretically produce is calculated by solving Maxwell's equations by the finite element method is a set of variables used to parameterize the description of the interface electronic state spatial distribution , and the interface electronic state distribution is represented as a linear combination of a series of preset basis functions :
[0042] The weights of the preset basis functions are used to describe which basis functions are superimposed to form the real electronic state distribution; the measured target signal is the target, and the parameters are automatically adjusted to minimize the objective function :
[0043] When the optimization converges, the parameter vector at the minimum of the objective function is taken as the target parameter vector, and the quantitative interface electronic state spatial distribution is obtained.
[0044] The embodiments of the present disclosure realize dynamic compensation of wavefront distortion of incident light based on iteration of the phase hologram, so that the reflected light formed by the reflection of the incident light after the sample interface reaches the best interference state with the reference light. The optimized phase hologram not only improves the signal quality of the final coherent light, but also serves as a quantitative basis for the wavefront modulation of the sample interface, and further inversion of the phase hologram can obtain the interface electronic state spatial distribution information of the sample, realizing the in-situ characterization method of synchronously obtaining the nonlinear optical response and the interface microscopic physical state of the material.
[0045] Based on the same inventive concept, the second embodiment of the present disclosure provides a detection system for center-symmetric material interface state space distribution, which mainly comprises: an incident light path assembly, a reference light path assembly, an exit light path assembly, a sample stage and a processor; wherein the incident light path assembly is used to generate a preset laser pulse and split the preset laser pulse to form a reference light and an incident light, the reference light is shot into the reference light path assembly, the incident light is modulated based on a phase grating based on a spatial light modulator, and the modulated incident light is irradiated onto the surface of a sample carried on the sample stage to form a reflected light; the reference light path assembly is used to modulate the reference light based on coherent matching; the exit light path assembly is used to combine the reflected light and the reference light, and collect the light intensity after the coherent of the reflected light and the reference light through a photodetector; the processor is used to judge whether the light intensity meets the convergence condition; in the case that the light intensity does not meet the convergence condition, the spatial light modulator is driven to iteratively optimize the phase grating until the light intensity modulated according to the optimized phase grating meets the convergence condition; in the case that the light intensity meets the convergence condition, the current phase grating is taken as a target phase grating; and the interface state space distribution information of the sample is determined according to the target phase grating.
[0046] Specifically, the system components of the embodiment mainly consist of the following components, as shown in Figure 3 The incident light path assembly comprises a laser light source 1, a first half-wave plate 2, a first polarizer 3, a first filter 4, a first beam splitter 5, a spatial light modulator 6, a first optical axis adjuster 7, a first lens adjustment frame 8 and a focusing lens 9 arranged in sequence; the reference light path assembly comprises a frequency doubling crystal 16, a second filter 17, a second half-wave plate 18, an attenuation plate 19, an optical path compensation device 20, a phase shifter 21 and a mirror 22 arranged in sequence; the exit light path assembly comprises a collimating mirror 23, a second lens adjustment frame 24, a second optical axis adjuster 25, a beam combiner 26, a second polarizer 27, a low-pass filter 28 and a photodetector 29 arranged in sequence, and the photodetector 29 can be a spectrometer or a single photon counter.
[0047] In actual detection, the laser light source 1 emits ultrashort pulse laser, the light beam passes through the first half-wave plate 2 to change the polarization direction, and then passes through the first polarizer 3 to strengthen the extinction ratio of the polarized light and the polarization characteristics of the polarized light; the laser output from the first polarizer 3 is incident into the first filter 4 to filter out stray light, and then passes through the first beam splitter 5 to divide the light beam into two beams, one of which is used as a signal beam to enter the spatial light modulator 6, and the other enters the coherent detection light path (corresponding to the reference light path assembly); in order to avoid distortion of the interface signal wavefront output from the sample, the signal beam enters the spatial light modulator 6 for phase modulation and then is incident into the focusing lens 9 to focus the laser onto the sample 13 on the sample stage 12 to generate a second harmonic, and the specific phase modulation process of the spatial light modulator 6 is as described in the first embodiment of the present disclosure; the combined light intensity measured by the last photodetector 29 is set as a performance index The embodiments are not repeated here.
[0048] In the coherent detection light path, the frequency doubling crystal 16, the second filter 17, the second half-wave plate 18, the output light beam intensity is controlled by the attenuator 19, and the intensity matching of the signal light is realized to achieve coherence, and then the light path compensation device 20 and the phase shifter 21 are further incident to the light path compensation device 20 and the phase shifter 21 to realize the coherence with the interface signal. In the exit light path, the signal reflected from the sample is collimated by the collimating mirror 23, the collimating mirror is adjusted by the objective lens adjustment frame 24, and the collimated light beam is further adjusted by the second optical axis adjuster 25. The adjusted light beam enters the beam combiner 26 and is combined with the light path emitted from the coherent detection light path, and the combined light is output. The polarization direction of the combined light is adjusted by the second polarizer 27, and then the second filter 28 is used to filter out the fundamental light, and finally the photoelectric detection device 29 is used for detection.
[0049] In some embodiments, the incident light path assembly further comprises a spot topography analyzer 11 for analyzing the focal spot intensity distribution of the received light beam from the beam splitter 10, and monitoring the topography of the signal light beam incident on the sample. In some embodiments, a microscope 14 and a height gauge 15 are arranged directly above the sample to observe the position of the light beam and measure the height of the sample.
[0050] The embodiments of the present application realize dynamic compensation of the wavefront distortion of the incident light based on the iteration of the phase hologram, so that the reflected light formed by the reflection of the incident light at the sample interface reaches the best interference state with the reference light. The optimized phase hologram not only improves the signal quality of the final coherent light, but also serves as a quantitative basis for the wavefront modulation of the sample interface. Further inversion of the phase hologram can obtain the interface electronic state spatial distribution information of the sample, and realize the in-situ characterization method of simultaneously obtaining the nonlinear optical response and the microphysical state of the material.
[0051] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present disclosure, and not to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present disclosure.
Claims
1. A method for detecting the spatial distribution of interface states in centrosymmetric materials, characterized in that, include: The preset laser pulse is split to form a reference beam and an incident beam; Construct a phase lattice diagram and modulate the incident light according to the phase lattice diagram; The interface of the sample is irradiated with modulated incident light to obtain reflected light; The intensity of the reflected light and the reference light after coherence is collected, and it is determined whether the intensity satisfies the convergence condition. If the light intensity does not meet the convergence condition, the phase lattice is iteratively optimized until the light intensity modulated according to the optimized phase lattice meets the convergence condition. If the light intensity satisfies the convergence condition, the current phase diagram is used as the target phase diagram; The interface state spatial distribution information of the sample is determined based on the target phase diagram.
2. The detection method according to claim 1, characterized in that, The phase diagram is constructed based on Zernike polynomials and their coefficient vectors.
3. The detection method according to claim 2, characterized in that, The Zernike polynomials are indexed using the Noll indexing method.
4. The detection method according to claim 2, characterized in that, The iterative optimization of the phase lattice diagram until the light intensity modulated according to the optimized phase lattice diagram satisfies the convergence condition includes: Set the gain coefficient and perturbation amplitude, and initialize the number of iterations; Generate a random perturbation vector based on the current iteration number; Based on the random perturbation vector, a positive perturbation is applied to the current coefficient vector to obtain a positive perturbation phase diagram; The incident light is modulated according to the positive perturbation phase diagram, and the positive perturbation light intensity is determined; Based on the random perturbation vector, a negative perturbation is applied to the current coefficient vector to obtain a negative perturbation phase diagram; The incident light is modulated according to the negative perturbation phase diagram, and the intensity of the negative perturbation light is determined; The light intensity gradient estimate is determined based on the positive and negative perturbation light intensities. The current coefficient vector is updated based on the gain coefficient and the light intensity gradient estimate. The light intensity of the reflected light and the reference light after coherence is re-acquired based on the updated coefficient vector. It is then determined whether the light intensity meets the convergence condition. If the light intensity does not meet the convergence condition, the iteration count is incremented by 1 and a new random perturbation vector is generated to iterate the current coefficient vector until the light intensity modulated by the phase diagram determined based on the current coefficient vector meets the convergence condition.
5. The detection method according to claim 4, characterized in that, Each element of the random perturbation vector independently follows a Bernoulli distribution, and is subject to a positive or negative perturbation based on the perturbation magnitude with equal probability.
6. The detection method according to any one of claims 1 to 5, characterized in that, Determining the interface state spatial distribution information of the sample based on the target phase hologram includes: Obtain the phase matrix of the target phase diagram, and reverse the sign of the phase matrix to obtain the inverted phase matrix; The inverted phase matrix is segmented to obtain a continuous absolute phase distribution; The optical system phase difference is removed from the absolute phase distribution to obtain the target signal; Based on the target signal, the interface state spatial distribution information of the sample is determined through forward simulation and backward iteration.
7. The detection method according to claim 6, characterized in that, The determination of the interface state spatial distribution information of the sample based on the target signal through forward simulation and backward iteration includes: Assume an interface electronic state distribution The theoretical second harmonic generated by the electronic state distribution is calculated by solving Maxwell's equations using the finite element method. , where the parameter vector Used to parameterize the spatial distribution of electronic states at the interface. Variables; The interface electronic state distribution is represented as a series of predefined basis functions. Linear combination: Using the target signal as the objective, the parameter vector is adjusted to optimize the objective function. : in, For target signal; The parameter vector when the objective function is minimized As the target parameter vector, the interface state spatial distribution information of the sample is determined. .
8. A detection system for the spatial distribution of interface states in centrosymmetric materials, characterized in that, include: Incident optical path assembly, reference optical path assembly, exit optical path assembly, sample stage, and processor; among which, The incident light path component is used to generate a preset laser pulse and split the preset laser pulse to form a reference light and an incident light. The reference light enters the reference light path component, and the incident light is modulated based on a spatial light modulator based on a phase diagram. The modulated incident light is then irradiated onto the surface of the sample supported on the sample stage to form reflected light. The reference optical path component is used to modulate the reference light based on coherent matching; The outgoing optical path assembly is used to combine the reflected light and the reference light, and to collect the intensity of the reflected light and the reference light after coherence through a photodetector. The processor is used to determine whether the light intensity meets the convergence condition; if the light intensity does not meet the convergence condition, it drives the spatial light modulator to iteratively optimize the phase symmetry until the light intensity modulated according to the optimized phase symmetry meets the convergence condition; if the light intensity meets the convergence condition, it uses the current phase symmetry as the target phase symmetry; and determines the interface state spatial distribution information of the sample according to the target phase symmetry.
9. The detection system according to claim 8, characterized in that, The incident optical path assembly includes, in sequence, a laser source, a first half-wave plate, a first polarizer, a first filter, a first beam splitter, a spatial light modulator, a first optical axis adjuster, a first lens adjustment frame, and a focusing lens; The reference optical path assembly includes, in sequence, a frequency doubling crystal, a second filter, a second half-wave plate, an attenuator, an optical path compensation device, a phase shifter, and a reflector; The outgoing optical path assembly includes, in sequence, a collimating lens, a second lens adjustment frame, a second optical axis adjuster, a beam combiner, a second polarizer, a low-pass filter, and a photodetector.
10. The detection system according to claim 8 or 9, characterized in that, Also includes: An altimeter and a microscope are positioned directly above the sample stage; The incident light path assembly also includes a second beam splitter disposed between the focusing lens and the sample stage, and the detection system also includes a spot morphology analyzer.