Method and apparatus for direct quantitative measurement of near-field electric field intensity, and storage medium

Abstract

The present disclosure relates to the technical field of electric field measurement, and comprises a method and apparatus for direct quantitative measurement of near-field electric field intensity, and a storage medium. The method comprises: controlling a tip of a scattering type scanning near-field optical microscope to move above a test point on the surface of a sample to be measured and in a first direction perpendicular to the surface of said sample, so as to obtain a first measurement result corresponding to each movement position; determining a first trend curve and a second trend curve on the basis of the first measurement result; determining a vibration equilibrium position of the tip on the basis of the first trend curve; determining shape parameters of an equivalent geometric shape of the tip on the basis of the second trend curve; controlling the tip to move in a second direction parallel to the surface of said sample to obtain a second measurement result; and determining the near-field electric field intensity of the surface of said sample on the basis of the second measurement result, the shape parameters, the vibration equilibrium position, and an electric field intensity measurement model. The near-field electric field intensity distribution on the surfaces of samples to be measured can be directly obtained, thereby achieving electric field intensity comparison between two scanning results.

Description

Method, device and storage medium for directly quantitatively measuring near-field electric field intensity

[0001] This application claims priority to the Chinese patent application No. 202411088463.8, filed on August 8, 2024, and entitled "Method, device and storage medium for directly quantitatively measuring near-field electric field intensity", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of electric field measurement, and particularly relates to a method, device and storage medium for directly quantitatively measuring near-field electric field intensity. BACKGROUND

[0003] Scanning near-field optical microscope (s-SNOM) is a scanning near-field optical microscope technology based on scattering principle. It uses a sharp metal-coated probe as a light scatterer to collect near-field optical information through the interaction between the probe and the sample surface. s-SNOM can be used to characterize nanomaterials, such as: to characterize surface plasmons, surface phonon polaritons and other electromagnetic waves, and the corresponding material range includes metals, dielectric materials, current two-dimensional materials, etc.

[0004] Specifically, the probe in s-SNOM is usually an atomic force microscope (AFM) tip, and the working principle of s-SNOM includes: when a beam of light irradiates the material surface of a sample, the energy of the light wave will excite the electrons or other carriers on the material surface, causing them to oscillate under the action of the light field. This oscillation will produce a near-field electric field distribution near the material surface, which is related to the dielectric properties of the material surface and reflects the response of the material to light. When the tip is placed in the near-field region of the material surface of the sample, the free electrons on the tip will oscillate, and this oscillation will produce polarization. The scattering signal caused by these oscillating electrons will be introduced into the remote detector, and the detector can measure the near-field electric field by analyzing the scattering signal.

[0005] However, each scan of s-SNOM can be under different scanning conditions, and the specific value of the coupling between the tip and the surface of the sample to be measured is unclear. Based on this, the intensity information (such as the intensity of surface waves or scattered light intensity) obtained by two scans cannot be directly compared. For example: for the Extraordinary Optical Transmission (EOT) or array coupling phenomenon, it is impossible to compare the electric field intensity of a single unit in different arrays.

[0006] SUMMARY

[0007] Therefore, the present disclosure provides a method and device for directly and quantitatively measuring near-field electric field intensity, and a storage medium, which can solve the problem that the near-field electric field intensity cannot be directly measured, and directly obtain the near-field electric field intensity distribution on the surface of a sample to be measured, thereby realizing the comparison of electric field intensity between two scanning results.

[0008] According to an aspect of the present disclosure, a method for directly and quantitatively measuring near-field electric field intensity is provided, which comprises:

[0009] controlling a tip of a scattering scanning near-field optical microscope to move above a test point on a surface of a sample to be measured in a first direction perpendicular to the surface of the sample to be measured, to obtain a first measurement result corresponding to each moving position;

[0010] determining a first asymptotic curve and a second asymptotic curve based on the first measurement result; wherein the first asymptotic curve is used to indicate the change relationship between the amplitude of the tip and the moving position; and the second asymptotic curve is used to indicate the change relationship between the near-field electric field formed between the tip and the surface of the sample to be measured and the moving position;

[0011] determining a vibration equilibrium position of the tip based on the first asymptotic curve;

[0012] determining a shape parameter of an equivalent geometric shape of the tip based on the second asymptotic curve;

[0013] controlling the tip to move in a second direction parallel to the surface of the sample to be measured, to obtain a second measurement result;

[0014] determining the near-field electric field intensity of the near-field electric field based on the second measurement result, the shape parameter, the vibration equilibrium position and a preset electric field intensity measurement model; wherein the electric field intensity measurement model is used to indicate the relationship between the second measurement result, the shape parameter, the vibration equilibrium position and the near-field electric field intensity.

[0015] In a possible implementation, the determination of the vibration equilibrium position of the tip based on the first asymptotic curve comprises:

[0016] determining a vibration equilibrium stage in the first asymptotic curve; wherein the vibration equilibrium stage refers to a stage in which the amplitude of the tip remains substantially unchanged with the change of the moving position;

[0017] determining the vibration equilibrium position based on the amplitude at the moving position corresponding to the vibration equilibrium stage.

[0018] In a possible implementation, the equivalent geometric shape comprises an equivalent sphere; correspondingly,

[0019] The shape parameter of the equivalent geometric shape of the needle tip is determined based on the second asymptotic curve, comprising:

[0020] The radius of the equivalent sphere is determined based on the second asymptotic curve and the electric field intensity measurement model, to obtain the shape parameter.

[0021] In a possible implementation, the electric field intensity measurement model is established based on the second measurement result, a needle tip scattering function and a signal amplification function; the near-field electric field intensity is in a positive correlation with the second measurement result, and in a negative correlation with an output result of the needle tip scattering function and an output result of the signal amplification function.

[0022] The output result of the needle tip scattering function is related to the shape parameter and the vibration balance position; the output result of the signal amplification function is related to a device parameter of the scattering-type scanning near-field optical microscope; during the measurement on the surface of the sample to be measured, the device parameter is a constant.

[0023] In a possible implementation, the needle tip scattering function is determined based on a distribution of a total electric field scattered by the needle tip in space.

[0024] In a possible implementation, the equivalent geometric shape comprises an equivalent sphere, correspondingly,

[0025] The needle tip scattering function is represented by the following formula: z(t) = z0 + z1 · cos(2πft);

[0026] wherein z0 represents the vibration balance position, z1 represents an amplitude of the needle tip, f represents a vibration frequency of the needle tip, a represents a radius of the equivalent sphere, Ω represents a receiving angle of a third parabolic mirror in the scattering-type scanning near-field optical microscope, the third parabolic mirror being used to collect a scattered signal after needle tip scattering; E total represents an electric field intensity of the total electric field scattered by the needle tip, r, θ, represent spherical coordinates of the total electric field in space, n represents a modulation coefficient of the scattering-type scanning near-field optical microscope, and i represents an imaginary unit.

[0027] In a possible implementation, the scattering-type scanning near-field optical microscope comprises a first light path and a second light path, the first light path being used to process a first light beam obtained after the laser is split, and the second light path being used to process a second light beam obtained after the laser is split.

[0028] The signal amplification function is determined based on an instrument function, wherein the device parameters in the instrument function include:

[0029] The permittivity and permeability in the air;

[0030] The ratio of the electric field intensity of the first light beam to the electric field intensity of the original light before the last beam splitter, wherein the last beam splitter is located in the first light path and the second light path;

[0031] The ratio of the electric field intensity of the second light beam to the electric field intensity of the original light before the last beam splitter;

[0032] The amplification coefficient of the detector for converting light into an electrical signal;

[0033] The first type of Bessel function;

[0034] The attenuation constant of all light paths; and

[0035] The beam area of the first light beam after passing through the diaphragm, wherein the first light path includes the diaphragm.

[0036] According to another aspect of the present disclosure, a device for directly and quantitatively measuring near-field electric field intensity is provided, the device comprising:

[0037] A laser emitter for emitting laser light;

[0038] A first beam splitter for splitting the received laser light into a first light beam and a second light beam;

[0039] A first light path comprising, in order along the beam propagation direction, a galvanometer mirror, a mirror, a diaphragm, a second beam splitter, and a first parabolic mirror, wherein the first light path processes the first light beam to obtain a processed first light beam, and the processed first light beam enters a detector;

[0040] A second light path comprising, in order along the beam propagation direction, a second parabolic mirror, a needle tip, a third parabolic mirror, the second beam splitter, and the first parabolic mirror, wherein the second light path processes the second light beam to obtain a processed second light beam, and the processed second light beam enters the detector;

[0041] A detector for converting the detected light beams into electrical signals, and processing the electrical signals to obtain measurement results, wherein the detected light beams include the processed first light beam and the processed second light beam;

[0042] A controller comprising a processor and a memory for storing processor-executable instructions;

[0043] The processor is configured to implement the above-described method when executing the instructions stored in the memory.

[0044] In a possible implementation, the second parabolic mirror is located below the surface of the sample to be measured, and the needle tip and the third parabolic mirror are located above the surface of the sample to be measured.

[0045] According to another aspect of the present disclosure, a non-transitory computer-readable storage medium is provided, which stores computer program instructions, wherein the computer program instructions, when executed by a processor, implement the method described above.

[0046] According to another aspect of the present disclosure, a computer program product is provided, which includes computer readable code, or a non-transitory computer readable storage medium carrying computer readable code, and when the computer readable code is run in a processor of an electronic device, the processor in the electronic device executes the method described above.

[0047] By controlling the needle tip of the scattering scanning near-field optical microscope to move above the test point on the surface of the sample to be measured in a first direction perpendicular to the surface of the sample to be measured, a first measurement result corresponding to each moving position is obtained; a first asymptote and a second asymptote are determined based on the first measurement result; a vibration balance position of the needle tip is determined based on the first asymptote; a shape parameter of the equivalent geometric shape of the needle tip is determined based on the second asymptote; the needle tip is controlled to move in a second direction parallel to the surface of the sample to be measured, and a second measurement result is obtained; and the near-field electric field intensity of the surface of the sample to be measured is determined based on the second measurement result, the shape parameter, the vibration balance position, and a preset electric field intensity measurement model; the electric field intensity measurement model is used to indicate the relationship between the second measurement result, the shape parameter, the vibration balance position, and the near-field electric field intensity; the problem that the near-field electric field intensity cannot be directly measured can be solved; the near-field electric field intensity distribution of the surface of the sample to be measured can be directly obtained, so that the electric field intensity comparison between two scanning results can be realized.

[0048] Other features and aspects of the present disclosure will become apparent from the following detailed description of example embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0049] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate example embodiments, features, and aspects of the present disclosure and serve to explain the principles of the present disclosure.

[0050] FIG. 1 shows a block diagram of an apparatus for directly quantitatively measuring a near-field electric field intensity according to an embodiment of the present disclosure;

[0051] FIG. 2 shows a flowchart of a method for directly quantitatively measuring a near-field electric field intensity according to an embodiment of the present disclosure;

[0052] FIG. 3 shows a schematic diagram of the movement of a needle tip in a first direction according to an embodiment of the present disclosure;

[0053] FIG. 4 shows a schematic diagram of a first asymptotic curve according to an embodiment of the present disclosure;

[0054] FIG. 5 shows a schematic diagram of a second asymptotic curve according to an embodiment of the present disclosure;

[0055] FIG. 6 shows a schematic diagram of quantitative results of near-field electric field intensity and simulation results according to an embodiment of the present disclosure;

[0056] FIG. 7 shows a schematic diagram of quantitative results of near-field electric field intensity and simulation results according to another embodiment of the present disclosure;

[0057] FIG. 8 shows a block diagram of a device for directly quantitatively measuring near-field electric field intensity according to an embodiment of the present disclosure;

[0058] FIG. 9 shows a block diagram of a device for directly quantitatively measuring near-field electric field intensity according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0059] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numbers in different drawings represent the same or similar elements. Although various aspects of embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0060] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0061] In addition, for the purpose of convenience and brevity, detailed descriptions of well-known devices, methods, procedures, components, and circuits will not be described in detail. It will be appreciated that the present disclosure can be practiced with the elements recited in the detailed description without those specifically recited elements.

[0062] FIG. 1 shows a block diagram of a device for directly quantitatively measuring near-field electric field intensity according to an embodiment of the present disclosure. As shown in FIG. 1, the device includes a laser emitter 110, a first beam splitter 120, a first optical path 130, a second optical path 140, a probe 150, and a controller (not shown).

[0063] The laser emitter 110 serves as a light source for emitting laser light (i.e., original light in the following). In one example, the laser emitter 110 is a He-Ne laser (Necsel), and in other embodiments, the laser emitter can also be of other types, which are not limited in the present embodiment. Optionally, the spot diameter of the laser light can be a value in the range of 2-100 μm, which is not limited in the present embodiment.

[0064] The first beam splitter 120 is used to divide the received laser light into a first light beam and a second light beam. Illustratively, after the laser light emitted by the laser emitter 110 is incident on the first beam splitter 120, a portion of the light is reflected to obtain the first light beam, and another portion of the light is transmitted to obtain the second light beam.

[0065] The first light path 130 includes, in sequence along the light beam propagation direction, a galvanometer 131, a mirror 132, an aperture 133, a second beam splitter 134, and a first parabolic mirror 135. The first light path 130 processes the first light beam to obtain a processed first light beam, which enters the detector 150.

[0066] The galvanometer 131 vibrates to cause the first light beam to scan in space to form a light beam track. By controlling the vibration frequency and amplitude of the galvanometer, the scanning speed and scanning range of the light beam can be controlled. Illustratively, the vibration frequency of the galvanometer 131 is M=303 Hz, and in other embodiments, the value of M can also be other values, which are not limited in the present embodiment. In the example shown in FIG. 1, the reflecting surface of the galvanometer 131 receives the first light beam and reflects it to the reflecting surface of the mirror 132, which is further reflected to the aperture 133 via the mirror 132.

[0067] The aperture 133 is used to limit the size of the light beam to prevent unnecessary light from entering. In one example, the light beam area of the first light beam processed by the aperture 133 is S R .

[0068] The second beam splitter 134 is used to transmit the first light beam processed by the aperture 133 to the first parabolic mirror 135, and the first parabolic mirror 135 is used to focus the light processed by the second beam splitter 134 to a focal point, at which the detector 150 is located to detect the processed first light beam.

[0069] The second light path 140 includes, in sequence along the light beam propagation direction, a second parabolic mirror 141, a needle tip 142, a third parabolic mirror 143, the second beam splitter 134, and the first parabolic mirror 135. The second light path 140 processes the second light beam to obtain a processed second light beam, which enters the detector 150.

[0070] The second parabolic mirror 141 is used to focus the second light beam to the needle tip 142.

[0071] The tip 142 is used to interact with the surface of the sample to be measured to form a near-field electric field between the tip 142 and the surface of the sample to be measured, and to make the tip 142 scatter the received second light beam to the third parabolic mirror 143.

[0072] The vibration of the tip 142 realizes the interaction with the surface of the sample to be measured, and the vibration parameters at least include the frequency and the amplitude. The frequency affects the rate of the interaction of the tip 142 with the sample to be measured, and the amplitude affects the proximity of the tip 142 to the sample to be measured. In other embodiments, the vibration parameters can also include the phase, which is used to reflect the mechanical properties of the interaction of the tip 142 with the sample, and the present embodiment does not limit the type of the vibration parameters. In one example, the frequency f of the vibration of the tip 142 can be 280 kHz, or a value approximately equal to 280 kHz, and the present embodiment does not limit the frequency of the vibration of the tip 142.

[0073] The tip 142 can be a tip coated with platinum-iridium (Pt-Ir), and in other embodiments, the material of the tip 142 can also be other materials, such as metals, silicon, etc., which can interact with the surface of the sample to be measured, and the present embodiment does not limit the material of the tip 142.

[0074] The third parabolic mirror 143 is used to collect the second light beam scattered by the tip 142, and focus the scattered second light beam to the second beam splitter 134. Correspondingly, the second beam splitter 134 is also used to reflect the light focused by the third parabolic mirror 143 to the second beam splitter 134 to the first parabolic mirror 135, so that the first parabolic mirror 135 focuses the light processed by the second beam splitter 134 to the focal point.

[0075] In the present embodiment, the first light path 130 is used to input the reference light to the detector 150, and the second light path 140 is used to irradiate the surface of the sample to be measured to generate a near-field electric field on the surface of the sample to be measured, and input the signal light to the detector 150 to determine the electric field intensity of the near-field electric field in combination with the reference light and the signal light.

[0076] The detector 150 is used to convert the detected light beam into an electrical signal, and process the electrical signal to obtain a measurement result. According to the light beam transmission principle of the first light path 130 and the second light path 140, the light beam detected by the detector 150 includes the processed first light beam and the processed second light beam.

[0077] The processing of the electrical signal includes amplifying the electrical signal and demodulating the electrical signal at the frequency nf±mM to obtain the measurement result. In one example, the measurement result includes the amplitude information and the phase information of the electric field detected by the detector.

[0078] Wherein, f represents the frequency of the tip vibration, M represents the vibration frequency of the galvanometer, n and m represent demodulation coefficients, n represents a main demodulation order, and m is a secondary demodulation order.

[0079] Optionally, the detector 150 can be a semiconductor detector 150 based on Mercury Cadmium Telluride (MCT) material, or can also be a Cadmium Telluride (CdTe) detector 150, a Mercury Cadmium Telluride (HgCdTe) detector 150, etc., and the type of the detector 150 is not limited in the embodiment.

[0080] The conventional s-SNOM supports detection of characterization of the surface material of the to-be-measured sample. The material characterization method generally includes: the surface wave (i.e. electromagnetic wave in the near-field region) of the material surface excited by the tip interferes with the incident light to form a fringe, the interval of the fringe is measured to obtain the wavelength of the surface wave, and the material properties are analyzed based on the wavelength, such as: analyzing the dielectric constant of the material, or the waveguide properties of the material. However, at present, when the surface material is characterized, the commonly used s-SNOM is under the condition of oblique incidence, and the oblique incidence will cause the problems of fixed spot area and phase difference. Based on this, in an example, the s-SNOM in the embodiment is a transmission type s-SNOM. That is, the second parabolic mirror is located below the surface of the to-be-measured sample, and the tip and the third parabolic mirror are located above the surface of the to-be-measured sample. At this time, the tip will not be directly excited by the light source, but will be irradiated to the tip after being transmitted through the to-be-measured sample, which can reduce the difficulty of fitting the equivalent geometry of the tip. At the same time, since the incident light path and the detection light path of the second light beam are decoupled, the irradiation area of the tip incident light can be adjusted to avoid the problem of fixed spot area. In addition, the second light beam is vertically incident from below the to-be-measured sample, so there is no difference in phase.

[0081] The controller is connected with the galvanometer, the tip and the detector 150 respectively, to control the vibration of the galvanometer and the tip, and obtain the measurement results obtained by the detector 150.

[0082] In the embodiment, the controller includes a processor and a memory for storing processor-executable instructions. Wherein, the processor is configured to execute the following steps when executing the instructions stored in the memory:

[0083] The tip of the scattering scanning near-field optical microscope is controlled to move above the test point on the surface of the to-be-measured sample along a first direction perpendicular to the surface of the to-be-measured sample, to obtain a first measurement result corresponding to each movement position;

[0084] determine a first asymptotic curve and a second asymptotic curve based on the first measurement result; wherein the first asymptotic curve is used to indicate a change relationship between the amplitude of the needle tip and the moving position; and the second asymptotic curve is used to indicate a change relationship between the near-field electric field formed between the needle tip and the surface of the sample to be measured and the moving position;

[0085] determine a vibration balance position of the needle tip based on the first asymptotic curve;

[0086] determine a shape parameter of the equivalent geometric shape of the needle tip based on the second asymptotic curve;

[0087] control the needle tip to move in a second direction parallel to the surface of the sample to be measured to obtain a second measurement result;

[0088] determine a near-field electric field intensity of the near-field electric field based on the second measurement result, the shape parameter, the vibration balance position and a preset electric field intensity measurement model; wherein the electric field intensity measurement model is used to indicate a relationship between the second measurement result, the shape parameter, the vibration balance position and the near-field electric field intensity.

[0089] The above-mentioned related descriptions are described in detail in the following method embodiments, and will not be described here.

[0090] In other embodiments, the controller can be implemented in the same device as the other components described above, such as an s-SNOM, or the controller can be an independent device in communication with the other components described above, and the implementation of the controller is not limited in this embodiment.

[0091] In this embodiment, the relationship between the second measurement result and the near-field electric field intensity of the surface of the sample to be measured is derived through the electric field intensity measurement model, and the near-field electric field intensity of the surface of the sample to be measured can be directly obtained using the second measurement result, and the near-field electric field intensity distribution of the surface of the sample to be measured is directly obtained, so that the electric field intensity comparison between the two scanning results can be realized.

[0092] Next, the method for directly and quantitatively measuring the near-field electric field intensity provided by the present application is described in detail. FIG. 2 shows a flowchart of a method for directly and quantitatively measuring the near-field electric field intensity according to an embodiment of the present disclosure. This embodiment takes the method for use in the device for directly and quantitatively measuring the near-field electric field intensity shown in FIG. 1, and is specifically used in the controller in the device. As shown in FIG. 2, the method comprises:

[0093] Step 201: Control the needle tip of the scattering scanning near-field optical microscope to move above the test point on the surface of the sample to be measured in a first direction perpendicular to the surface of the sample to be measured to obtain a first measurement result corresponding to each moving position.

[0094] In one example, the surface of the sample to be measured is obtained by processing a plasmonic surface of gold, silver or the like. Optionally, the processing process comprises: preparing a plasmonic surface with a preset thickness by using a thin film growth method; and processing the sample to be measured on the plasmonic surface by using a focused ion beam (FIB).

[0095] The thin film growth method includes, but is not limited to, methods such as electron beam evaporation deposition or magnetron sputtering, and the embodiment does not limit the implementation manner of the thin film growth method. The preset thickness can be 100 nm or other thickness, and the embodiment does not limit the thickness of the plasmonic surface.

[0096] Optionally, the sample to be measured can be a pattern, such as a geometric shape or the like, or can also be a structure, such as a micro-nano structure or the like, and the embodiment does not limit the type of the sample to be measured.

[0097] The test point on the surface of the sample to be measured can be any point on the surface of the sample to be measured or a specified point on the surface of the sample to be measured, and the embodiment does not limit the setting manner of the test point.

[0098] In the embodiment, the tip moves within a preset distance range above the surface of the sample to be measured, the minimum value of the preset distance range is greater than 0, and the maximum value is less than the order of magnitude of 100 nanometers, so that the tip and the surface of the sample to be measured can interact to form a near-field electric field.

[0099] Optionally, the control of the movement of the tip in the first direction perpendicular to the surface of the sample to be measured comprises: controlling the tip to move upward (i.e., move away from the surface of the sample to be measured) from a first moving position, and each time the distance of upward movement is a first distance interval, until the tip moves to a second moving position. Alternatively, the control of the movement of the tip in the first direction perpendicular to the surface of the sample to be measured comprises: controlling the tip to move downward (i.e., move close to the surface of the sample to be measured) from the second moving position, and each time the distance of downward movement is a second distance interval, until the tip moves to the first moving position.

[0100] The first moving position is determined based on the minimum distance between the tip and the surface of the sample to be measured, and the second moving position is determined based on the maximum distance between the tip and the surface of the sample to be measured. The first distance interval and the second distance interval are the same or different, and the embodiment does not limit the value of the first distance interval and the second distance interval.

[0101] Taking the downward movement of the tip from the second moving position as an example, the process of obtaining the first measurement result is shown in FIG. 3. According to FIG. 3, the tip moves within a moving distance range d to form a near-field electric field E i The measurement is performed to obtain the first measurement result at each moving position.

[0102] At step 202, a first asymptotic curve and a second asymptotic curve are determined based on the first measurement result; the first asymptotic curve is used to indicate a change relationship between the amplitude of the needle tip and the moving position; and the second asymptotic curve is used to indicate a change relationship between the near-field electric field formed between the needle tip and the surface of the sample to be measured and the moving position.

[0103] The first measurement result includes a measurement result of the scattering scanning near-field optical microscope at each moving position. Illustratively, the first measurement result includes the amplitude of the needle tip corresponding to each moving position and the electric field intensity detected by the probe at the measurement point.

[0104] Illustratively, the amplitude of the needle tip can be measured by a component of the AFM module in the s-SNOM system, such as by a laser detection system in the AFM module.

[0105] After obtaining the amplitude of the needle tip corresponding to each moving position, the first asymptotic curve can be generated based on the respective moving positions and the corresponding amplitudes. For example, the first asymptotic curve generated based on the first measurement result is shown in FIG. 4. As shown in FIG. 4, the moving position d of the needle tip above the test point is within the range of 0-80 nm, and accordingly, the amplitude z1(d) of the needle tip gradually increases from 60 nm, and then reaches a balanced value z c .

[0106] Similarly, after obtaining the detected electric field intensity corresponding to each moving position, the second asymptotic curve can be generated based on the respective moving positions and the corresponding electric field intensities. For example, the second asymptotic curve generated based on the first measurement result is shown in FIG. 5. As shown in FIG. 5, the moving position d of the needle tip above the test point is within the range of 0-80 nm, and accordingly, as the distance between the moving position d and the test point gradually increases, the detected electric field intensity S 3,2 gradually decreases. In FIG. 5, the circles represent the measured electric field intensity corresponding to each moving position, and the curve connecting the circles represents the second asymptotic curve generated by fitting.

[0107] At step 203, a vibration balance position of the needle tip is determined based on the first asymptotic curve.

[0108] The vibration balance position refers to an initial position at which the amplitude of the needle tip does not change with the moving position.

[0109] In one example, determining the vibration balance position of the needle tip based on the first asymptotic curve includes: determining a vibration balance stage in the first asymptotic curve; and determining the vibration balance position based on the amplitude at the moving position corresponding to the vibration balance stage. The vibration balance stage refers to a stage in which the amplitude of the needle tip remains substantially unchanged as the moving distance changes.

[0110] In this embodiment, "substantially consistent" means that the amplitude of the tip remains unchanged or the variation is less than or equal to a preset allowable fluctuation threshold.

[0111] Illustratively, determining the vibration balance stage in the first asymptotic curve comprises: comparing the amplitude corresponding to the i th moving position with the amplitude corresponding to the i+1 th moving position to obtain a variation of the amplitude; if the variation is less than or equal to the allowable fluctuation threshold, setting i=i+1, and performing again the step of comparing the amplitude corresponding to the i th moving position with the amplitude corresponding to the i+1 th moving position to obtain a variation of the amplitude; if the n continuous variations are all less than or equal to the allowable fluctuation threshold, determining that the curve part indicated by each moving position corresponding to the n variations is the vibration balance stage. Wherein, n is a preset positive integer.

[0112] In other embodiments, the manner of determining the vibration balance stage in the first asymptotic curve can also be other manners, such as: calculating the slope of each point on the first asymptotic curve, and determining that the point and the curve part after the point are the vibration balance stage when the slope is less than a preset slope threshold, and the embodiment does not limit the manner of determining the vibration balance stage.

[0113] Illustratively, determining the vibration balance position based on the moving position corresponding to the vibration balance stage comprises: determining the amplitude corresponding to the initial moving position of the vibration balance stage as the vibration balance position. For example, in FIG. 4, the amplitude z corresponding to the initial moving position d of the vibration balance stage is determined as the vibration balance position. c The amplitude z c corresponding to the initial moving position d of the vibration balance stage is determined as the vibration balance position.

[0114] In other embodiments, the vibration balance position can also be the average of the amplitudes corresponding to each moving position in the vibration balance stage, and the embodiment does not limit the manner of determining the vibration balance position.

[0115] Step 204, determining the shape parameter of the equivalent geometric shape of the tip based on the second asymptotic curve.

[0116] In the traditional near-field electric field research between the tip and the surface of the sample to be measured, the tip and the surface of the sample to be measured are generally simulated as a dipole model, at this time, the geometric shape of the tip is not considered, which can cause the problem that the analysis result of the near-field electric field is not accurate enough. The real geometric shape of the tip is relatively complex and is difficult to express through a mathematical model. Based on this, in this embodiment, the real geometric shape of the tip is replaced by an equivalent geometric shape of the tip, the calculation complexity of the equivalent geometric shape is lower than that of the real geometric shape of the tip, the geometric shape of the tip is considered, the accuracy of the near-field electric field analysis is ensured, and the problem that the geometric shape of the tip is difficult to determine is avoided, and the calculation complexity is reduced.

[0117] The equivalent geometric shape is a geometric shape that can simulate the scattering function of the tip, for example, the equivalent geometric shape includes but is not limited to an equivalent spherical shape, or an equivalent ellipsoidal shape, and the embodiment is not limited to the implementation of the equivalent geometric shape.

[0118] In the embodiment, the equivalent geometric shape includes an equivalent spherical shape, and correspondingly, the shape parameter of the equivalent geometric shape of the tip is determined based on the second asymptotic curve, including determining the radius of the equivalent spherical shape based on the second asymptotic curve and the electric field intensity measurement model, to obtain the shape parameter.

[0119] Specifically, the term representing the near-field electric field intensity in the electric field intensity measurement model is normalized to convert the term representing the near-field electric field intensity into a constant, to obtain the converted electric field intensity measurement model; the detected electric field intensity corresponding to each moving position in the second asymptotic curve is input into the converted electric field intensity measurement model, to obtain the radius of the equivalent spherical shape corresponding to the second asymptotic curve. For example, the equivalent spherical radius a corresponding to the second asymptotic curve shown in FIG. 5 is 22.6 nm.

[0120] The related content of the electric field intensity measurement model is described in detail below, and the term representing the near-field electric field intensity can be normalized to 1 or other numerical values, and the embodiment is not limited to the normalization result.

[0121] Optionally, the step 204 can be executed after the step 203, or can be executed before the step 203, or can be executed simultaneously with the step 203, and the embodiment is not limited to the execution order of the steps 203 and 204.

[0122] In step 205, the tip is controlled to move in a second direction parallel to the surface of the sample to be measured, to obtain a second measurement result.

[0123] When the scattering-type scanning near-field optical microscope scans the surface of the sample to be measured, the tip moves along a working plane parallel to the surface of the sample to be measured, and the moving direction on the working plane is the second direction. In other words, the first direction is perpendicular to the second direction.

[0124] The second measurement result includes the measurement result of the scattering-type scanning near-field optical microscope corresponding to different surface positions on the surface of the sample to be measured. Illustratively, the second measurement result includes the electric field intensity of the electric field detected by the detector after the near-field electric field scattered by the tip corresponding to each surface position.

[0125] Controlling the tip to move in the second direction parallel to the surface of the sample to be measured to obtain the second measurement result includes: controlling the tip to vibrate at a preset vibration frequency and move in the second direction parallel to the surface of the sample to be measured to obtain the second measurement result output by the detector.

[0126] At step 206, the near-field electric field intensity of the surface of the sample to be measured is determined based on the second measurement result, the shape parameter, the vibration balance position, and a preset electric field intensity measurement model, wherein the electric field intensity measurement model is used to indicate the relationship between the second measurement result, the shape parameter, the vibration balance position, and the near-field electric field intensity.

[0127] The near-field electric field intensity refers to the electric field intensity of the near-field electric field formed between the needle tip and the surface of the sample to be measured. Since the near-field electric field is scattered by the needle tip and is processed by the detection light path in the second light path before being detected by the detector, the second measurement result detected by the detector is related to not only the near-field electric field intensity itself, but also the scattering ability of the needle tip and the device parameters of the scattering near-field optical microscope. Based on this, the electric field intensity measurement model is established based on the change relationship between the near-field electric field intensity, the scattering ability of the needle tip, the device parameters, and the second measurement result.

[0128] The scattering ability of the needle tip is simulated by an equivalent geometric shape, that is, the scattering ability of the needle tip is related to the shape parameter and the vibration balance position of the equivalent geometric shape. Correspondingly, the electric field intensity measurement model is used to indicate the relationship between the second measurement result, the shape parameter, the vibration balance position, and the near-field electric field intensity.

[0129] In one example, the second measurement result S n,m may be represented by the following formula:

[0130] wherein ε0 is the dielectric constant in air, μ0 is the magnetic permeability in air, σ is the amplification coefficient of the detector, the detector is used to convert the optical signal into an electrical signal, J m (γ) is the first kind of Bessel function with m order (for example: m = 2, in other embodiments, m can also be other values), the value of γ is a constant. The first kind of Bessel function is used to describe the incident laser, generally, the laser emitter 110 works in TEM00 mode (i.e. a kind of transverse electromagnetic mode (Transverse Electromagnetic Mode, TEM) of laser), based on this, the laser can be described by the Bessel function. η is the attenuation constant of the first light path and the second light path; E t2 is the electric field of the second light beam entering the detector after being processed by the second light path; E r2 is the electric field of the first light beam entering the detector after being processed by the first light path; S D is the beam size of the light entering the detector, which is the same for the first light beam and the second light beam, n and m are the demodulation orders of the output signal, n is the main demodulation order, and m is the secondary demodulation order.

[0131] E r2 and E t2It can be determined by the following formula:

[0132] Among them, v r S represents the ratio of the electric field intensity of the first beam before it passes through the second beam splitter to the electric field intensity of the original light; R E represents the beam area of ​​the first beam after passing through the aperture; r1 This represents the electric field intensity of the first beam before it passes through the first parabolic mirror; v t S represents the ratio of the electric field intensity of the second beam before it passes through the second beam splitter to the electric field intensity of the original beam; S E represents the beam area of ​​the second beam after passing through the third parabolic mirror. t1 This represents the electric field intensity of the second beam collected by the third parabolic mirror.

[0133] Among them, E t1 It can be determined by the following formula:

[0134] Among them, S S E represents the beam area of ​​the second beam after passing through the third parabolic mirror. nf，0 Let ξ(z0, z1, f, a) represent the near-field electric field strength, and let ξ(z0, z1, f, a) represent the tip scattering function, which is related to the vibration equilibrium position z0, the tip amplitude z1, the tip vibration frequency f, and the shape parameter a.

[0135] Substituting the above formulas into the expression for the second measurement result, we obtain the electric field strength measurement model as follows: S n，m =E nf，0 ·ξ(z0,z1,f,a)·F; F=F0E r1 ;

[0136] S n，m This represents the second measurement result, where ε0 is the permittivity of air, μ0 is the permeability of air, σ is the magnification factor of the detector, and J... m (γ) is a Bessel function of the first kind, having an order of m (e.g., m = 2, but m can be other values ​​in other embodiments), and the value of γ is a constant; η is the attenuation constant of the first and second optical paths; n and m are the demodulation orders of the output signal, where n is the primary demodulation order and m is the secondary demodulation order; v r S represents the ratio of the electric field intensity of the first beam before it passes through the second beam splitter to the electric field intensity of the original light; R E represents the beam area of ​​the first beam after passing through the aperture; r1 This represents the electric field intensity of the first beam before it passes through the first parabolic mirror; v ta ratio of an electric field intensity of the second light beam before passing through the second beam splitter to an electric field intensity of the original light.

[0137] According to the above formula, the electric field intensity measurement model is established based on the second measurement result, the tip scattering function ξ(z0, z1, f, a) and the signal amplification function F; the near-field electric field intensity is positively correlated with the second measurement result, and is negatively correlated with an output result of the tip scattering function and an output result of the signal amplification function.

[0138] The output result of the tip scattering function is related to the shape parameter and the vibration equilibrium position; the output result of the signal amplification function is related to the device parameter of the scattering type scanning near-field optical microscope; and the device parameter is a constant during the measurement of the surface of the sample to be measured.

[0139] Specifically, according to the above process, the signal amplification function includes an instrument function F0 and an electric field intensity E r1 of the first light beam before passing through the first parabolic mirror obtained by each measurement.

[0140] a dielectric constant ε0 and a magnetic permeability μ0 in the air;

[0141] a ratio v r of the electric field intensity of the first light beam before the last beam splitter (i.e., the second beam splitter) to the electric field intensity of the original light;

[0142] a ratio v t of the electric field intensity of the second light beam before the last beam splitter (i.e., the second beam splitter) to the electric field intensity of the original light;

[0143] an amplification coefficient σ of the detector, the detector being used to convert light into an electric signal;

[0144] a first kind of Bessel function J m (γ) with m order, m being a positive integer and γ being a preset value;

[0145] an attenuation constant η of all light beam paths; and

[0146] a light beam area S R of the first light beam after passing through the diaphragm.

[0147] For example, the values of the device parameters are as follows: the ratio v r of the electric field intensity of the first light beam before the last beam splitter to the electric field intensity of the original light is 0.581, the ratio v t of the electric field intensity of the second light beam to the electric field intensity of the original light is 0.747, the amplification coefficient σ of the MCT detector is 1.24×10 6 V / W, and the Bessel function J mIn (γ), m = 2, γ = 2.46; attenuation constant η = 0.47 for all light paths; beam area S of the first light beam after the diaphragm R = 1.96 x 10 -5 m 2 .

[0148] In other embodiments, the values of the device parameters can also be set to other values according to measurement requirements, and the embodiments are not limited in value of the device parameters.

[0149] In the embodiments, the needle-tip scattering function is determined based on the distribution of the total electric field scattered by the needle tip in space.

[0150] Taking the equivalent geometric shape of the needle tip as an equivalent sphere for example, correspondingly, the needle-tip scattering function can be expressed by the following formula: z(t) = z0+ z1·cos(2πft);

[0151] wherein z0represents the vibration equilibrium position, z1represents the amplitude of the needle tip, f represents the vibration frequency of the needle tip, a represents the radius of the equivalent sphere, Ω represents the receiving angle of the third parabolic mirror in the scattering-type scanning near-field optical microscope, n represents the main demodulation order of the output signal, i represents the imaginary unit, E total represents the electric field intensity of the total electric field scattered by the needle tip, r, θ, represents the spatial spherical coordinates of the total electric field scattered by the needle tip, used to describe the distribution of the total electric field in space.

[0152] wherein the second measurement result further includes the amplitude z1of the needle tip, and the amplitude z1of the needle tip is measured by the AFM module in the s-SNOM system, and the related description is referred to the above, which will not be repeated herein.

[0153] Based on the above electric field intensity measurement model, the second measurement result S n，m and z1, the shape parameter a, and the vibration equilibrium position z0are input into the electric field intensity measurement model, and the near-field electric field intensity E nf，0 is obtained.

[0154] In summary, the method for directly and quantitatively measuring near-field electric field intensity provided in the embodiment can control the tip of the scattering scanning near-field optical microscope to move above the test point on the surface of the sample to be measured in a first direction perpendicular to the surface of the sample to be measured, and obtain a first measurement result corresponding to each moving position; determine a first asymptotic curve and a second asymptotic curve based on the first measurement result; determine a vibration balance position of the tip based on the first asymptotic curve; determine a shape parameter of the equivalent geometric shape of the tip based on the second asymptotic curve; control the tip to move in a second direction parallel to the surface of the sample to be measured, and obtain a second measurement result; and determine the near-field electric field intensity of the surface of the sample to be measured based on the second measurement result, the shape parameter, the vibration balance position, and a preset electric field intensity measurement model, wherein the electric field intensity measurement model is used to indicate the relationship between the second measurement result, the shape parameter, the vibration balance position, and the near-field electric field intensity. The method can solve the problem that the near-field electric field intensity cannot be directly measured, directly obtain the near-field electric field intensity distribution of the surface of the sample to be measured, and thus can realize the comparison of electric field intensities between two scanning results.

[0155] In addition, the parameters of the input electric field intensity measurement model in the application can be obtained by measuring the surface of the sample to be measured, without constructing a proportional relationship based on a reference sample to reconstruct an electric field, so as to reduce the complexity of electric field intensity measurement and improve the calculation efficiency.

[0156] In addition, the shape parameter of the equivalent geometric shape is used to determine the electric field intensity measurement model, the calculation complexity of the equivalent geometric shape is lower than that of the real geometric shape of the tip, the geometric shape of the tip is considered, the accuracy of near-field electric field analysis is ensured, the problem that the geometric shape of the tip is difficult to determine is avoided, and the calculation complexity is reduced.

[0157] Next, the near-field electric field intensity directly and quantitatively measured by the application is compared with the simulation result, and reference is made to FIG. 6. (a) and (d) in FIG. 6 represent the topography of the surface of the sample to be measured, (b) represents the near-field electric field intensity actually measured on (a), (c) represents the simulation result of the near-field electric field of the surface of the sample to be measured on (a), (e) represents the near-field electric field intensity actually measured on the surface of the sample to be measured in the dashed box in (d), and (f) represents the simulation result of the near-field electric field of the surface of the sample to be measured in the dashed box in (d).

[0158] As shown in FIG. 6, the near-field electric field intensity directly and quantitatively measured by the application is basically consistent with the simulation result, and thus it is known that the near-field electric field intensity has high accuracy.

[0159] Referring to FIG. 7, taking a nanodisk as an example, FIG. 7(a) shows the morphology of the nanodisk, FIG. 7(b) shows the second measurement result of the scattering-type scanning near-field optical microscope in the transmission mode of the nanodisk, FIG. 7(c) shows a comparison between the quantitative result obtained by quantitatively measuring the second measurement result in the line in FIG. 7(b) and the simulation result, FIG. 7(d) shows a 3D graph constructed based on the quantitative result of the nanodisk, and FIG. 7(e) shows a 3D graph constructed based on the simulation result of the nanodisk.

[0160] As can be seen from FIG. 7, the quantitative result of the nanodisk is basically consistent with the simulation result, and the measurement method of the near-field electric field intensity has high accuracy.

[0161] FIG. 8 is a block diagram of a device for directly quantitatively measuring near-field electric field intensity, according to an embodiment of the present application. The device includes a first control module 810, a curve generation module 820, a position determination module 830, a parameter determination module 840, a second control module 850, and an electric field measurement module 860.

[0162] The first control module 810 is configured to control the tip of the scattering-type scanning near-field optical microscope to move above a test point on the surface of a sample to be measured in a first direction perpendicular to the surface of the sample to be measured, so as to obtain a first measurement result corresponding to each moving position.

[0163] The curve generation module 820 is configured to determine a first asymptotic curve and a second asymptotic curve based on the first measurement result. The first asymptotic curve is used to indicate the change relationship between the amplitude of the tip and the moving position. The second asymptotic curve is used to indicate the change relationship between the near-field electric field formed between the tip and the surface of the sample to be measured and the moving position.

[0164] The position determination module 830 is configured to determine the vibration balance position of the tip based on the first asymptotic curve.

[0165] The parameter determination module 840 is configured to determine the shape parameter of the equivalent geometric shape of the tip based on the second asymptotic curve.

[0166] The second control module 850 is configured to control the tip to move in a second direction parallel to the surface of the sample to be measured, so as to obtain a second measurement result.

[0167] The electric field measurement module 860 is configured to determine the near-field electric field intensity of the surface of the sample to be measured based on the second measurement result, the shape parameter, the vibration balance position, and a preset electric field intensity measurement model. The electric field intensity measurement model is used to indicate the relationship between the second measurement result, the shape parameter, the vibration balance position, and the near-field electric field intensity.

[0168] The related description is shown in the above method embodiment.

[0169] In some embodiments, the apparatus provided by the embodiments of the present disclosure has functions or contains modules which can be used to execute the methods described in the above method embodiments, and the specific implementation can refer to the description of the above method embodiments. For brevity, it will not be repeated here.

[0170] The embodiments of the present disclosure also provide a computer readable storage medium having computer program instructions stored therein, and the computer program instructions are executed by a processor to implement the above method. The computer readable storage medium can be a volatile or non-volatile computer readable storage medium.

[0171] The embodiments of the present disclosure also provide an electronic device, comprising: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to implement the above method when executing the instructions stored in the memory.

[0172] The embodiments of the present disclosure also provide a computer program product, comprising computer readable code or a non-volatile computer readable storage medium carrying computer readable code, when the computer readable code is run in the processor of the electronic device, the processor in the electronic device executes the above method.

[0173] FIG. 9 is a block diagram illustrating an apparatus 1900 for directly quantitatively measuring near-field electric field strength, according to an exemplary embodiment. For example, the apparatus 1900 can be provided as a server or a terminal device. Referring to FIG. 9, the apparatus 1900 includes a processing component 1922, which further includes one or more processors, and a memory resource represented by a memory 1932 for storing instructions, such as an application program, executable by the processing component 1922. The application program stored in the memory 1932 can include one or more than one module each corresponding to a set of instructions. In addition, the processing component 1922 is configured to execute the instructions to perform the above method.

[0174] The apparatus 1900 can also include a power supply component 1926 configured to perform power management of the apparatus 1900, a wired or wireless network interface 1950 configured to connect the apparatus 1900 to a network, and an input output interface 1958 (I / O interface). The apparatus 1900 can operate based on an operating system stored in the memory 1932, such as Windows Server TM , Mac OS X TM , Unix TM , Linux TM , FreeBSD TM or the like.

[0175] In an example embodiment, a non-transitory computer-readable storage medium, such as memory 1932 including computer program instructions, is also provided that can be executed by the processing component 1922 of the apparatus 1900 to perform the above-described methods.

[0176] Embodiments of the disclosure have been described above, with the understanding that these descriptions are exemplary only, and are not intended to be exhaustive or to limit the embodiments disclosed to the precise descriptions used. Changes and modifications can be made by those of ordinary skill in the art, once armed with the above descriptions and teachings, without departing from the spirit and scope of the described embodiments. The choice of words in this document is not intended to limit the scope of the embodiments disclosed, but rather to best describe the principles of each embodiment in its most practical and preferred implementation.

Claims

1. A method of directly quantitatively measuring near field electric field strength, characterized by, The method comprises: controlling a needle tip of a scattering scanning near-field optical microscope to move above a test point on a surface of a sample to be measured in a first direction perpendicular to the surface of the sample to be measured, to obtain a first measurement result corresponding to each moving position; determining a first asymptotic curve and a second asymptotic curve based on the first measurement result; wherein the first asymptotic curve is used to indicate a change relationship between an amplitude of the needle tip and the moving position; and the second asymptotic curve is used to indicate a change relationship between a near-field electric field formed between the needle tip and the surface of the sample to be measured and the moving position; determining a vibration balance position of the needle tip based on the first asymptotic curve; determining a shape parameter of an equivalent geometric shape of the needle tip based on the second asymptotic curve; controlling the needle tip to move in a second direction parallel to the surface of the sample to be measured, to obtain a second measurement result; determining a near-field electric field intensity of the near-field electric field based on the second measurement result, the shape parameter, the vibration balance position and a preset electric field intensity measurement model; wherein the electric field intensity measurement model is used to indicate a relationship between the second measurement result, the shape parameter, the vibration balance position and the near-field electric field intensity.

2. The method of claim 1, wherein, The method comprises: determining a vibration balance stage in the first asymptotic curve; wherein the vibration balance stage refers to a stage in which the amplitude of the needle tip remains substantially unchanged as the moving position changes; determining the vibration balance position based on the amplitude at the moving position corresponding to the vibration balance stage.

3. The method of claim 1, wherein, The equivalent geometric shape comprises an equivalent sphere; correspondingly, The method comprises: determining a radius of the equivalent sphere based on the second asymptotic curve and the electric field intensity measurement model, to obtain the shape parameter.

4. The method of claim 1, wherein, The electric field intensity measurement model is established based on the second measurement result, a needle tip scattering function and a signal amplification function; the near-field electric field intensity has a positive correlation with the second measurement result, and has a negative correlation with an output result of the needle tip scattering function and an output result of the signal amplification function; wherein the output result of the needle tip scattering function is related to the shape parameter and the vibration balance position; the output result of the signal amplification function is related to a device parameter of the scattering scanning near-field optical microscope; and the device parameter is a constant during measurement of the surface of the sample to be measured.

5. The method of claim 4, wherein, The needle tip scattering function is determined based on a distribution of a total electric field scattered by the needle tip in space.

6. The method of claim 5, wherein, The equivalent geometric shape comprises an equivalent sphere, correspondingly, The needle tip scatter function is represented by the following equation: z(t) = z0 + z1 · cos(2πft); wherein z0 represents the vibration balance position, z1 represents the amplitude of the needle tip, f represents the vibration frequency of the needle tip, a represents the radius of the equivalent sphere, Ω represents the receiving angle of the third parabolic mirror in the scattering scanning near-field optical microscope, the third parabolic mirror being used to collect the scattered signal after scattering of the needle tip; E total represents the electric field intensity of the total electric field scattered by the needle tip, r, θ, wherein r represents a spatial spherical coordinate of the total electric field, n represents a modulation coefficient of the scattering scanning near-field optical microscope, and i represents an imaginary unit.

7. The method of claim 4, wherein, The scattering scanning near-field optical microscope comprises a first light path and a second light path; the first light path is used to process a first light beam obtained after a laser beam is split; and the second light path is used to process a second light beam obtained after the laser beam is split. The signal amplification function is determined based on an instrument function, wherein the device parameters in the instrument function include: dielectric constant and magnetic permeability in air; a ratio of an electric field intensity of the first light beam to an electric field intensity of the original light before a last beam splitter, the last beam splitter being located in the first light path and the second light path; a ratio of an electric field intensity of the second light beam to an electric field intensity of the original light before the last beam splitter; an amplification coefficient of a detector for converting light into an electric signal; a first type of Bessel function; an attenuation constant of all light paths; and a beam area of the first light beam after a diaphragm, the first light path including the diaphragm.

8. An apparatus for directly quantitatively measuring near field electric field strength, characterized by, The apparatus includes: a laser emitter for emitting laser light; a first beam splitter for splitting the received laser light into a first light beam and a second light beam; a first light path including, in order along a beam propagation direction, a galvanometer mirror, a mirror, a diaphragm, a second beam splitter, and a first parabolic mirror, the first light path processing the first light beam to obtain a processed first light beam entering a detector; a second light path including, in order along the beam propagation direction, a second parabolic mirror, a needle tip, a third parabolic mirror, the second beam splitter, and the first parabolic mirror, the second light path processing the second light beam to obtain a processed second light beam entering the detector; a detector for converting a detected light beam into an electric signal, and processing the electric signal to obtain a measurement result, wherein the detected light beam includes the processed first light beam and the processed second light beam; a controller including a processor and a memory for storing processor-executable instructions; wherein the processor is configured to implement the method of any one of claims 1 to 7 when executing the instructions stored in the memory.

9. The apparatus of claim 8, wherein, The second parabolic mirror is located below a surface of the sample to be measured, and the needle tip and the third parabolic mirror are located above the surface of the sample to be measured.

10. A non-transitory computer readable storage medium having stored thereon computer program instructions, wherein, The computer program instructions, when executed by the processor, implement the method of any one of claims 1 to 7. The computer program instructions, when executed by the processor, implement the method of any one of claims 1 to 7.

Images