A second harmonic characterization system based on coherent probing technique

Abstract

The application relates to a second harmonic characterization system based on a coherent detection technology, comprising: an incident light path assembly for wavelength, power control, polarization direction adjustment and filtering of laser pulses, and then the laser pulses are divided into two beams, one of which is irradiated onto a sample after optical axis adjustment and focusing in the incident light path, and the SHG carrying defect information is generated after the light beam is modulated by the sample; the other beam enters a coherent detection light path; a coherent detection light path assembly is used for frequency doubling, filtering, polarization direction and intensity adjustment, optical path compensation and phase shifting of the light beam entering the coherent detection light path, so as to form a reference light beam introducing an optical path and phase disturbance; an exit light path assembly is used for collimating optical axis adjustment of the signal light beam reflected by the sample, and then the signal light beam is combined with the reference light beam; the combined light is coherent on a detector, and the interface signal is extracted by determining a specific phase matching state after phase scanning. The application realizes interface signal extraction of a non-centrosymmetric material system, and expands the use scene of the SHG characterization technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nonlinear optical characterization, and particularly relates to a second harmonic characterization system based on coherent detection technology. BACKGROUND

[0002] In the field of modern optics and optoelectronics, second harmonic generation (SHG) technology has become an important nonlinear optical phenomenon, which is widely used in material analysis, biological imaging and optical communication, etc. Second harmonic refers to the process that when light waves pass through a nonlinear medium, a new light wave with a frequency twice that of the original light is generated. This process not only depends on the nonlinear properties of the medium, but also is affected by wavelength, light intensity and phase matching, etc., so that the SHG technology becomes a powerful tool for detecting material properties and internal structure. For example, the SHG technology can be used to locate and identify the structure defects such as stacking faults and dislocations of the wafer, and to characterize the non-uniform strain information in the material. At the same time, the time-dependent second harmonic can obtain the information of interface state density and fixed oxide charge.

[0003] When the SHG technology is applied in the wafer characterization field, the bulk signal of the non-centrosymmetric material system is strong, so that the interface signal carrying the defect information is submerged in the strong bulk signal, which affects the accurate measurement of the defect information. Therefore, the existing SHG technology is not applicable in the non-centrosymmetric material system with strong bulk signal, which greatly restricts the development and application of the technology. SUMMARY

[0004] In view of the above analysis, the application aims to disclose a second harmonic characterization system based on coherent detection technology, which uses coherent detection technology to extract the interface signal by the difference in phase between the second harmonic interface signal and the bulk signal.

[0005] The application discloses a second harmonic characterization system based on coherent detection technology, which comprises an incident light path assembly, an outgoing light path assembly, a coherent detection light path assembly, a sample and a sample stage.

[0006] The incident light path assembly is used to control the wavelength, power, polarization direction and filter of the main laser pulse, and then split the laser pulse into two beams. One beam is used as a signal beam to adjust the optical axis and focus on the sample on the sample stage after being irradiated, and the light beam is modulated by the sample to generate SHG carrying defect information. The other beam enters the coherent detection light path.

[0007] The coherent detection light path assembly is used to frequency double, filter, adjust the polarization direction and intensity, compensate the optical path and phase shift the light beam entering the coherent detection light path, so as to form a reference light beam with introduced optical path and phase disturbance.

[0008] The exit light path component is used for collimating the signal light beam reflected by the sample, adjusting the optical axis, and then combining the signal light beam with the reference light beam; the combined light is polarized and filtered to realize coherence on the detector, and then photoelectric detection is performed;

[0009] When the reference light beam with the introduced optical path and phase disturbance is consistent with the polarization direction, optical path and phase of the interface reflected light beam, the light beams are coherent, and the SHG characterization of the interface signal is detected by photoelectric detection.

[0010] Further, the sample belongs to a non-centrosymmetric material system including silicon carbide, gallium nitride and diamond.

[0011] Further, the incident light path component comprises a laser, a first half-wave plate, a first polarizer, a first filter, a beam splitter, a first beam adjuster and a focusing mirror.

[0012] The laser is used to generate incident linearly polarized ultrashort laser pulses, which are output to the first half-wave plate.

[0013] The first half-wave plate is used to change the polarization direction of the incident laser beam according to the test requirements.

[0014] The first polarizer is used to strengthen the extinction ratio of the light beam output by the first half-wave plate, and to strengthen the polarization characteristics of the polarized light.

[0015] The first filter is used to filter the light beam output by the first polarizer, and to filter out stray light other than the wavelength of the laser output by the laser.

[0016] The beam splitter is used to split the light beam output by the first filter into two beams, one of which is used as a signal light beam to enter the first beam adjuster, and the other of which enters the coherent detection light path.

[0017] The first beam adjuster is used to further adjust the optical axis of the incoming signal light beam to obtain a signal light beam that meets the test conditions.

[0018] The focusing mirror is used to focus the light beam output by the first beam adjuster onto the sample on the sample stage to generate a second harmonic.

[0019] Further, the incident light path component further comprises a beam splitter and a spot topography analyzer.

[0020] The beam splitter is located between the focusing mirror and the sample, and is used to split a part of the signal light beam focused on the sample to the spot topography analyzer.

[0021] The spot topography analyzer is used to analyze the focal spot intensity distribution of the received light beam split from the beam splitter, and to monitor the topography of the signal light beam incident on the sample.

[0022] Further, a microscope and a height gauge are arranged right above the sample;

[0023] The position of the light beam irradiation is observed by the microscope arranged right above the sample, and the height of the sample is measured by the height gauge arranged right above the sample.

[0024] Further, the coherent detection light path assembly comprises a frequency doubling crystal, a second filter, a second half-wave plate, an attenuating plate, an optical path compensation device and a phase shifter;

[0025] The frequency doubling crystal is used for frequency doubling the split light entering the coherent detection light path to generate a reference light beam carrying a second harmonic;

[0026] The second filter is used for filtering out the fundamental light from the light beam output by the frequency doubling crystal;

[0027] The second half-wave plate is used for adjusting the polarization direction of the light beam output by the second filter to be the same as that of the signal light beam;

[0028] The attenuating plate is used for controlling the intensity of the output light beam to complete the intensity matching of the signal light to realize coherence;

[0029] The optical path compensation device is used for compensating the optical path of the light beam output by the second half-wave plate;

[0030] The phase shifter is used for changing the phase of the light beam output by the optical path compensation device;

[0031] After frequency doubling, filtering, polarization direction and intensity adjustment by the coherent detection light path assembly, and after optical path compensation and phase shifting, a reference light beam is obtained, which has the same frequency, amplitude, polarization direction, introduced optical path and phase disturbance as the signal light beam; the reference light beam enters the exit light path assembly to combine with the signal light beam reflected by the sample.

[0032] Further, the exit light path assembly comprises a collimating mirror, an objective lens adjustment frame, a second light beam adjuster, a combiner, a second polarizer, a second filter and a detection device;

[0033] The collimating mirror is used for collimating the signal light beam reflected by the sample; the SHG signal light beam reflected by the sample carries defect information;

[0034] The objective lens adjustment frame is used for adjusting the position of the collimating mirror;

[0035] The second light beam adjuster is used for further adjusting the optical axis of the light beam output by the collimating mirror;

[0036] The combiner is used for combining the signal light beam output from the second light beam adjuster with the reference light beam entering the combiner to output a combined light;

[0037] The second polarizer is used for filtering the combined light in a tunable polarization direction component and ensuring that the vibration directions of the light beams on the detector are consistent, thereby optimizing the coherent effect;

[0038] The second filter is a short-pass filter used for short-pass filtering the combined light output from the second polarizer, transmitting short-wavelength light and reflecting long-wavelength light; the fundamental light is reflected, and the combined second-harmonic light beam is output to the detection device;

[0039] The detection device is a photoelectric detection device used for photoelectrically detecting the combined second-harmonic light beam entering.

[0040] Further, the sample stage further comprises a circular arc guide rail, an incident arm, an outgoing arm, a first tangential stepper motor and a second tangential stepper motor.

[0041] The circular arc guide rail is located directly above the sample stage; the incident arm and the outgoing arm are slidably arranged on the circular arc guide rail and can slide on the circular arc guide rail around the center point of the sample stage.

[0042] The incident arm is a support structure of the incident light path assembly, and the outgoing arm is a support structure of the outgoing light path assembly; by controlling the positions of the incident arm and the outgoing arm on the circular arc guide rail, the incident angle of the signal light beam incident to the sample is determined, and the outgoing light path assembly is located in the reflected light beam of the sample, so that the sample detection under the set incident angle is realized.

[0043] The first tangential stepper motor is connected with the incident arm and drives the incident arm to slide in the direction perpendicular to the circular arc guide rail, thereby changing the focal point position of the incident light path.

[0044] The second tangential stepper motor is connected with the outgoing arm and drives the outgoing arm to slide in the direction perpendicular to the circular arc guide rail, thereby changing the position of the collimating mirror in the outgoing light path and ensuring the collimation state of the light beam in the outgoing light path.

[0045] Further, the sample stage is provided with a motion module, so that the sample moves in space to enable the laser to characterize the entire region of the sample.

[0046] The motion module comprises an XY plane motion module, a Z-axis compensation module and a rotation module around the Z-axis; the XY motion module is used for adjusting the position of the measured material, so that the second-harmonic multi-thread detection system can complete step-by-step scanning during operation; the Z-axis compensation module is used for compensating for the system deviation caused by different sample thicknesses; and the rotation module around the Z-axis is used for rotating the measured material around the detection center point to adjust the azimuth angle in the detection process and obtain the dependence of the SHG of the measured material on the azimuth angle.

[0047] Further, the control unit is further included;

[0048] The control unit is configured to control the controllable mechanical devices including the circular arc guide rail, the first and second tangential stepper motors, the first and second light beam adjusters, the sample stage, the height gauge, and the objective adjustment frame, to adjust the light path state according to the required incident angle and sample thickness, and to ensure the SHG signal intensity.

[0049] The present application can achieve one of the following beneficial effects:

[0050] Compared with the existing second harmonic characterization system, the system introduces coherent detection technology to extract bulk signal and interface signal in a non-centrosymmetric material system, and further expands the use scenarios of the second harmonic characterization technology.

[0051] Furthermore, the controllable mechanical devices are used to adjust the light path state when the incident angle and sample thickness change, and to ensure the signal intensity. BRIEF DESCRIPTION OF DRAWINGS

[0052] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments thereof, and together with the description serve to explain the principles of the application.

[0053] Figure 1 The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments thereof, and together with the description serve to explain the principles of the application.

[0054] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments thereof, and together with the description serve to explain the principles of the application. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present application will be specifically described below in conjunction with the accompanying drawings, wherein the drawings constitute a part of this application and are used to illustrate the principles of the embodiments of the present application.

[0056] One embodiment of the present application discloses a second harmonic characterization system based on coherent detection technology, as shown in Figure 1 The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments thereof, and together with the description serve to explain the principles of the application.

[0057] The incident light path assembly, the emergent light path assembly, the coherent probe light path assembly, the sample and the sample stage;

[0058] The incident light path assembly is used for splitting the main laser pulse into two beams after wavelength control, power control, polarization direction adjustment and filtering, one of which is used for irradiating the sample on the sample stage after optical axis adjustment and focusing in the incident light path, and the other of which enters the coherent probe light path;

[0059] The coherent probe light path assembly is used for forming the reference beam with introduced optical path and phase disturbance after frequency doubling, filtering, polarization direction and intensity adjustment, optical path compensation and phase shifting of the beam entering the coherent probe light path;

[0060] The emergent light path assembly is used for collimating and adjusting the optical axis of the signal beam reflected by the sample, and then combining the signal beam with the reference beam; and the combined light is subjected to polarization direction strengthening and filtering, and then coherent detection is realized on the detector and photoelectric detection is performed;

[0061] When the polarization direction, optical path and phase of the reference beam with introduced optical path and phase disturbance are consistent with those of the interface reflected beam, the beams are coherent, and the SHG of the interface signal is detected through photoelectric detection.

[0062] Specifically, the sample belongs to a non-centrosymmetric material system including silicon carbide, gallium nitride and diamond.

[0063] Specifically, the incident light path assembly comprises a laser, a first half-wave plate, a first polarizer, a first filter, a beam splitter, a first beam adjuster and a focusing mirror.

[0064] The laser is used for generating an incident linearly polarized ultrashort laser pulse, which is output to the first half-wave plate.

[0065] Preferably, the linearly polarized ultrashort laser pulse has a wavelength of 800 nm and a pulse width of 100 fs.

[0066] The first half-wave plate is used for changing the polarization direction of the incident laser beam according to test requirements.

[0067] The first polarizer is used for strengthening the extinction ratio of the light beam output by the first half-wave plate, and strengthening the polarization characteristics of the polarized light.

[0068] The first filter is used for filtering the light beam output by the first polarizer, and filtering out stray light other than the wavelength of the laser output by the laser.

[0069] The beam splitter is used to split the light beam output by the first filter into two beams, one of which enters the first beam adjuster as a signal light beam, and the other enters the coherent detection light path;

[0070] The first beam adjuster is used to further adjust the optical axis of the entering signal light beam to obtain a signal light beam meeting the test conditions.

[0071] The focusing mirror is used to focus the light beam output by the first beam adjuster onto the sample on the sample stage to generate a second harmonic.

[0072] Preferably, the incident light path assembly further comprises a beam splitter and a spot topography analyzer.

[0073] The beam splitter is located between the focusing mirror and the sample, and is used to split a part of the signal light beam focused on the sample to the spot topography analyzer.

[0074] The spot topography analyzer is used to analyze the focal spot intensity distribution of the received light beam split from the beam splitter, and monitor the topography of the signal light beam incident on the sample.

[0075] By monitoring the topography of the signal light beam, it is determined whether it is a Gaussian distribution; in the preferred scheme, a spatial light modulator can also be added in front of the spot topography analyzer to shape the light beam into a special light beam, such as a flat-top light beam.

[0076] In a more preferred scheme, a microscope and an altimeter are arranged directly above the sample.

[0077] The microscope arranged directly above the sample is used to observe the position of the light beam irradiation; and the altimeter arranged directly above the sample is used to measure the height of the sample.

[0078] Specifically, the coherent detection light path assembly comprises a frequency doubling crystal, a second filter, a second half-wave plate, an attenuator, an optical path compensation device, and a phase shifter.

[0079] The frequency doubling crystal is used to frequency-double the split light entering the coherent detection light path to generate a reference light beam carrying a second harmonic.

[0080] The second filter is used to filter out the fundamental light from the light beam output by the frequency doubling crystal.

[0081] The second half-wave plate is used to adjust the polarization direction of the light beam output by the second filter to be the same as that of the signal light beam.

[0082] The attenuator is used to control the intensity of the output light beam to complete the intensity matching of the signal light to achieve coherence.

[0083] The optical path compensation device is configured for compensating the optical path of the light beam output by the second half-wave plate.

[0084] The phase shifter is configured for changing the phase of the light beam output by the optical path compensation device.

[0085] After the frequency doubling, filtering, polarization direction and intensity adjustment of the coherent detection light path assembly, the reference light beam with the same frequency, amplitude, polarization direction, optical path and phase disturbance as the signal light beam is obtained after the optical path compensation and phase change, and the reference light beam enters the exit light path assembly to combine with the signal light beam reflected by the sample.

[0086] The reference light beam is introduced into the optical path and phase disturbance, and is used for searching the reference light beam coherent with the interface signal or bulk signal carrying SHG reflected by the sample.

[0087] In order to enable the reference light beam to align and enter the exit light path assembly to combine, the coherent detection light path assembly further comprises a light path adjustment device, for example, a plane mirror or other device capable of changing the light path, so that the reference light beam can enter the combining device in the exit light path assembly, and the light path adjustment device should be used in cooperation with the optical path compensation device to ensure that the optical path of the reference light beam matches the optical path of the signal light beam from beam splitting to beam combining.

[0088] Specifically, the exit light path assembly comprises a collimating mirror, an objective lens adjustment frame, a second light beam adjuster, a combiner, a second polarizer, a second filter and a detection device.

[0089] The collimating mirror is configured for collimating the signal light beam reflected by the sample, and the SHG signal light beam reflected by the sample carries defect information.

[0090] The objective lens adjustment frame is configured for adjusting the position of the collimating mirror.

[0091] The second light beam adjuster is configured for further adjusting the optical axis of the light beam output by the collimating mirror.

[0092] The combiner is configured for outputting the combined light after combining the signal light beam output from the second light beam adjuster with the reference light beam entering the combiner.

[0093] The second polarizer is configured for screening the adjustable polarization direction component of the combined light and ensuring that the vibration directions of the light beams on the detector are consistent, thereby optimizing the coherent effect.

[0094] The second filter is a short-pass filter configured for performing short-pass filtering on the combined light output by the second polarizer, transmitting short-wavelength light and reflecting long-wavelength light; the fundamental frequency light is reflected, and the combined second harmonic light beam is output to the detection device.

[0095] The detection device is a photoelectric detection device, which is used for photoelectric detection of the incoming combined second harmonic light beam.

[0096] Preferably, the photoelectric detection device is a spectrometer / single photon counter.

[0097] Preferably, the exit light path assembly further comprises an objective lens adjusting frame of the collimating mirror, which is used for adjusting the position of the collimating mirror; after the parameters including the incident angle of the signal light beam and the thickness of the sample are changed, the position of the collimating mirror is adjusted to satisfy the collimation of the reflected light beam of the sample.

[0098] Since the interface signal and the bulk signal of SHG are simultaneously carried in the reflected light beam when the sample of a non-centrosymmetric material system is detected, and the positions of the interface signal and the bulk signal of SHG are different, the optical path and the phase are different, in the implementation process of the second harmonic characterization system based on the coherent detection technology in the embodiment, the optical path compensation device and the phase shifter of the coherent detection light path assembly are adjusted to perform the matching optical path scanning and the matching phase scanning, then the coherence with the interface signal of SHG and the coherence with the bulk signal of SHG occur in the combined light in the beam combiner, the detection results under the corresponding coherence are obtained after the coherent results are detected by the detection device, and the coherence with the interface signal of SHG and the coherence with the bulk signal of SHG are distinguished according to the different optical path lengths and the different detection waveforms, and the optical path compensation value of the optical path compensation device and the phase shift value of the phase shifter in the two cases.

[0099] The optical path compensation value of the optical path compensation device and the phase shift value of the phase shifter are set to the value of the coherence with the interface signal of SHG, and then the SHG extraction of the interface signal of the sample is realized.

[0100] Similarly, if the SHG of the bulk signal needs to be extracted, the optical path compensation value of the optical path compensation device and the phase shift value of the phase shifter can be set to the value of the coherence with the bulk signal of SHG.

[0101] In the preferred scheme, the circular arc guide rail, the incident arm and the exit arm, the first tangential stepper motor and the second tangential stepper motor;

[0102] The circular arc guide rail is located directly above the sample table; the incident arm and the exit arm are slidably assembled on the circular arc guide rail and can slide on the circular arc guide rail around the center point of the sample table.

[0103] The incident arm is a support structure of the incident light path assembly, and the exit arm is a support structure of the exit light path assembly; by controlling the positions of the incident arm and the exit arm on the circular arc guide rail, the incident angle of the signal light beam incident to the sample is determined, and the exit light path assembly is located in the reflected light beam of the sample, so that the sample detection under the set incident angle is realized.

[0104] The coherent detection light path assembly is located in a space surrounded by the circular arc guide rail, the incident arm and the exit arm; the reference light beam output by the phase shifter is reflected by a mirror into the beam combiner of the exit light path assembly;

[0105] The first tangential stepper motor is connected with the incident arm and drives the incident arm to slide in the direction perpendicular to the circular arc guide rail, so as to change the focal point position of the incident light path;

[0106] The second tangential stepper motor is connected with the exit arm and drives the exit arm to slide in the direction perpendicular to the circular arc guide rail, so as to change the position of the collimating mirror in the exit light path and ensure the collimation state of the light beam in the exit light path.

[0107] In the preferred scheme, the sample stage is provided with a motion module, so that the sample (measured material) moves in space to enable the laser to characterize the entire region of the sample;

[0108] The motion module comprises an XY plane motion module, a Z-axis compensation module and a rotation module around the Z-axis; the XY motion module is used to adjust the position of the measured material, so that the secondary harmonic multi-thread detection system can complete step scanning during operation; the Z-axis compensation module is used to compensate for the system deviation caused by different sample thicknesses, and the rotation module around the Z-axis is used to rotate the measured material around the detection center point, so as to adjust the azimuth angle in the detection process and obtain the dependence of the measured material SHG on the azimuth angle.

[0109] After the light beam enters the measured material, the secondary harmonic wave emitted will carry the defect information of the sample due to the nonlinear effect of the material.

[0110] In the preferred scheme, a control unit is further included.

[0111] The control unit is used to control the controllable mechanical devices including the circular arc guide rail, the first and second tangential stepper motors, the first and second light beam adjusters, the sample stage, the height gauge and the objective lens adjustment frame, so as to adjust the light path state according to the parameter requirements including the required incident angle and the sample thickness, and ensure the SHG signal intensity.

[0112] For example, when the sample of different thickness is replaced, the height information fed back by the height gauge is used to adjust the height of the sample stage, so as to maintain the optimal measurement height of the system.

[0113] In summary, compared with the existing secondary harmonic characterization system, the secondary harmonic characterization system based on the coherent detection technology disclosed in the embodiment introduces the coherent detection technology, realizes the extraction of the bulk signal and the interface signal in the non-centrosymmetric material system, and further expands the use scene of the secondary harmonic characterization technology.

[0114] And, by controllable mechanical device, ensure that the light path system realizes the adjustment to the light path state when the incident angle, sample thickness and other parameters change, and ensures the signal intensity.

[0115] The above merely provides the preferred but not limiting embodiment of the present application, and any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A second harmonic characterization system based on coherent detection technology, characterized in that: include: Incident light path component, output light path component, coherent detection light path component, sample and sample stage; The incident light path component is used to perform wavelength control, power control, polarization direction adjustment and filtering on the main laser pulse, and then split it into two beams of light. One beam is used as a signal beam in the incident light path, and then the optical axis is adjusted and focused before irradiating the sample on the sample stage. The beam is modulated by the sample to generate SHG carrying defect information; the other beam enters the coherent detection light path; The coherent detection optical path component is used to perform frequency doubling, filtering, polarization direction and intensity adjustment, optical path compensation and phase shifting on the light beam entering the coherent detection optical path, thereby forming a reference beam that introduces optical path and phase disturbances; The output optical path component is used to collimate the signal beam reflected by the sample, adjust the optical axis, and then combine it with the reference beam; after the combined beam is polarized and filtered, it is coherent on the detector and photoelectric detection is performed; When the reference beam with introduced optical path and phase perturbations is consistent with the polarization direction, optical path and phase of the beam reflected from the sample interface, beam coherence occurs, and the SHG characterization of the interface signal is detected by photoelectric detection.

2. The second harmonic characterization system based on coherent detection technology according to claim 1, characterized in that: The samples belong to a non-centrosymmetric material system including silicon carbide, gallium nitride and diamond.

3. The second harmonic characterization system based on coherent detection technology according to claim 1, characterized in that: The incident light path assembly includes: a laser, a first half-wave plate, a first polarizer, a first filter, a beam splitter, a first beam adjuster and a focusing mirror; The laser is used to generate an ultrashort laser pulse with incident linear polarization and output it to the first half-wave plate; The first half-wave plate is used to change the polarization direction of the incident laser beam according to test requirements; The first polarizer is used to enhance the extinction ratio of the light beam output by the first half-wave plate, thereby enhancing the polarization characteristics of the polarized light; The first filter is used to filter the light beam output by the first polarizer to remove stray light other than the laser wavelength output by the laser; The beam splitter is used to split the light beam output by the first filter into two beams, one of which enters the first beam adjuster as a signal beam, and the other enters the coherent detection optical path; The first beam adjuster is used to further adjust the optical axis of the incoming signal beam to obtain a signal beam that meets the test conditions; The focusing mirror is used to focus the light beam output by the first beam adjuster onto the sample on the sample stage to generate second harmonic.

4. The second harmonic characterization system based on coherent detection technology according to claim 3, characterized in that: The incident light path components also include: a beam splitter and a light spot profile analyzer; The beam splitter is located between the focusing mirror and the sample, and is used to split a portion of the signal light beam focused on the sample to the light spot profile analyzer; The light spot profile analyzer is used to analyze the focal spot intensity distribution of the light beam received from the spectroscope and to monitor the profile of the signal light beam incident on the sample.

5. The second harmonic characterization system based on coherent detection technology according to claim 4, characterized in that: Set up a microscope and altimeter directly above the sample; The position of the light beam is observed by a microscope placed just above the sample; the height of the sample is measured by a height gauge placed just above the sample.

6. The second harmonic characterization system based on coherent detection technology according to claim 3, characterized in that: The coherent detection optical path component includes: a frequency doubling crystal, a second filter, a second half-wave plate, an attenuation plate, an optical path compensation device and a phase shifter; The frequency doubling crystal is used to frequency-double the split light entering the coherent detection optical path to generate a reference beam carrying the second harmonic; The second filter is used to filter out the fundamental frequency light of the light beam output by the frequency doubling crystal; The second half-wave plate is used to adjust the polarization direction of the light beam output by the second filter to be the same as the polarization direction of the signal light beam; The attenuation plate is used to control the intensity of the output light beam to achieve intensity matching of the signal light and achieve coherence; The optical path compensation device is used to perform optical path compensation on the light beam output by the second half-wave plate; The phase shifter is used to change the phase of the light beam output by the optical path compensation device; After frequency doubling, filtering, polarization direction and intensity adjustment by the coherent detection optical path component, and then optical path compensation and phase shifting, a reference beam is obtained, which has the same frequency, amplitude, and polarization direction as the signal beam and introduces optical path and phase disturbances; the reference beam enters the output optical path component and is combined with the signal beam reflected by the sample.

7. The second harmonic characterization system based on coherent detection technology according to claim 6, characterized in that: The output optical path assembly includes: a collimating lens, an objective lens adjustment frame, a second beam adjuster, a beam combiner, a second polarizer, a second filter and a detection device; The collimating mirror is used to collimate the signal beam reflected by the sample; the SHG signal beam reflected by the sample carries defect information; The objective lens adjustment frame is used to adjust the position of the collimating lens; The second beam adjuster is used to further adjust the optical axis of the light beam output by the collimator; The beam combiner is configured to combine the signal beam output from the second beam adjuster and the reference beam entering the beam combiner, and output a combined beam; The second polarizer is used to screen the components of the combined light beam with adjustable polarization direction and ensure that the vibration direction of the light beam on the detector is consistent, thereby optimizing the coherence effect; The second filter is a short-pass filter, which is used to perform short-pass filtering on the combined light beam output by the second polarizer, transmit short wavelengths and reflect long wavelengths; reflect the fundamental frequency light and output the combined second harmonic light beam to the detection device; The detection device is a photoelectric detection device, which is used to perform photoelectric detection on the incoming combined second harmonic light beam.

8. The second harmonic characterization system based on coherent detection technology according to any one of claims 1 to 7, characterized in that: It also includes: an arc guide rail, an incident arm, an exit arm; a first tangential stepping motor and a second tangential stepping motor; The arc guide rail is located directly above the sample stage; the incident arm and the output arm are slidably assembled on the arc guide rail, and both can slide on the arc guide rail around the center point of the sample stage; The incident arm is the supporting structure of the incident light path assembly, and the output arm is the supporting structure of the output light path assembly. By controlling the positions of the incident arm and the output arm on the arc guide rail, the incident angle of the signal light beam incident on the sample is determined, and the output light path assembly is positioned in the reflected light beam of the sample, thereby realizing sample detection at the set incident angle. The first tangential stepping motor is connected to the incident arm, driving the incident arm to slide in the direction of the vertical arc guide rail to change the focal position of the incident light path; The second tangential stepping motor is connected to the output arm, driving the output arm to slide in the direction of the vertical arc guide rail, changing the position of the collimating mirror in the output light path, and ensuring the collimation state of the light beam in the output light path.

9. The second harmonic characterization system based on coherent detection technology according to claim 8, characterized in that: The sample stage is equipped with a motion module to move the sample in space, allowing the laser to characterize the entire area of ​​the sample; The motion module includes: an XY plane motion module, a Z-axis compensation module and a rotation module around the Z axis; the XY motion module is used to adjust the position of the material under test so that the second harmonic multi-threaded detection system can complete step scanning during operation; the Z-axis compensation module is used to compensate for the system deviation caused by different sample thicknesses, and the rotation module around the Z axis rotates the material under test around the detection center point to adjust the azimuth angle during the detection process and obtain the dependence of the SHG of the material under test on the azimuth angle.

10. The second harmonic characterization system based on coherent detection technology according to claim 9, characterized in that: Also included: a control unit; The control unit is used to control controllable mechanical devices including the arc guide, the first and second tangential stepping motors, the first and second beam adjusters, the sample stage, the altimeter, and the objective lens adjustment frame, and adjust the optical path state according to parameter requirements including the incident angle and sample thickness required for the test to ensure the SHG signal intensity.

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