Second harmonic interface separation device based on self-coherence technology

Abstract

The invention provides a second harmonic interface separation device based on a self-coherence technology, and the device comprises an incident light path system which is used for regulating and controlling the polarization direction of a light beam and filtering stray light, so that the light beam is focused on a sample placed on a sample stage; the emergent light path system is used for collimating and filtering light beams emitted by the sample; and the second harmonic self-coherence system is used for dividing the light beam into a transmission light beam and a reflection light beam which can generate an interference effect, so that the resolvability of the signal is enhanced. According to the embodiment, interference light signals of different depths of the sample are obtained by regulating and controlling the optical path difference and the phase difference of the light beams, and material interface signals and body signals are selectively extracted, so that the problem of symmetry confusion is solved, and defect information in the material is obtained.

Description

Technical Field

[0001] This invention relates to the technical field of non-centrosymmetric material detection, and in particular to a second harmonic interface separation device based on self-coherence technology. Background Technology

[0002] Second harmonic generation (SHG) is a nonlinear optical microscopy technique developed in recent years that uses high-intensity laser irradiation to generate second-order polarization in materials. Among numerous characterization methods, SHG has demonstrated its ability to characterize the electric field and structural properties of material interfaces due to its non-destructive testing, high stability, and ease of operation. For example, this technique can be used to accurately locate and identify structural defects such as stacking faults and dislocations in silicon carbide (SiC) wafers, thereby revealing information about non-uniform strain in the material. Furthermore, by studying time-dependent SHG signals, important information about interface state density and fixed oxide charges can be provided. These characteristics make SHG technology a promising field for applications in materials science.

[0003] While current second harmonic generation (SHG) technology demonstrates strong capabilities in characterizing the electric fields and structural properties of material interfaces, significant technical bottlenecks remain in practical applications. The most prominent issue is the often strong bulk second harmonic signal in non-centrosymmetric materials, and the fact that the bulk signal and surface signal share the same symmetry characteristics in some materials. This makes it difficult to directly separate the pure surface signal using traditional methods. This signal aliasing severely restricts the accurate characterization of material interfaces, particularly when studying structural defects such as stacking faults and dislocations in silicon carbide (SiC) wafers, as it fails to effectively distinguish the signal responses generated by interface defects from those generated by bulk defects. Summary of the Invention

[0004] The summary section of this invention provides a brief overview of the concepts, which will be described in detail in the detailed description section that follows. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0005] Some embodiments of the present invention provide a second harmonic interface separation device based on self-coherent technology to solve the technical problems mentioned in the background section above.

[0006] Some embodiments of the present invention provide a second harmonic interface separation device based on self-coherence technology, including an incident optical path system for controlling the polarization direction of the beam and filtering stray light, so that the beam is focused onto a sample placed on a sample stage, wherein the sample is a non-centrosymmetric material. The outgoing optical path system is used to collimate and filter the light beam emitted from the sample. The second harmonic self-coherent system is used to split a light beam into a transmitted beam and a reflected beam that can produce an interference effect. By adjusting the optical path difference and phase difference of the beam, the interface signal and volume signal of the sample can be selectively extracted.

[0007] Optionally, the incident optical path system includes a laser, a half-wave plate, a first polarizer, a filter, and an emitting objective lens; The half-wave plate is used to control the polarization direction of the beam; the first polarizer is used to further enhance the polarization characteristics of the beam; the filter is used to filter the beam; and the emission objective is used to focus the beam onto the sample.

[0008] Optionally, the incident light path system further includes a beam splitter and a light spot morphology analyzer; The beam splitter is positioned between the focusing lens and the sample, so that the light beam is split into two paths after passing through the beam splitter. One beam is focused onto the sample, and the other beam is incident on the spot morphology analyzer. The beam spot morphology analyzer is used to analyze the focal spot intensity distribution of the incident beam and monitor the morphology of the signal beam incident on the sample.

[0009] Optionally, a height measuring instrument / observation mirror is also provided above the sample stage to obtain the height information of the sample being tested.

[0010] Optionally, the outgoing optical path system is used to receive the light beam emitted from the sample, including a probe objective and a filter; The detection objective lens is used to collimate the outgoing light beam; the filter is used to remove the fundamental frequency light from the collimated light beam while retaining the second harmonic.

[0011] Optionally, the output optical path system further includes an objective lens adjustment frame and a beam adjuster. The probe objective lens is mounted on the objective lens adjustment frame for fine-tuning the probe objective lens; the beam adjuster is positioned between the probe objective lens and the filter for fine-tuning the output beam.

[0012] Optionally, the second harmonic self-coherent system includes a beam splitter, a fixed mirror, a movable mirror, a phase shifter, and a second polarizer. The beam splitter is used to split the incident beam into a transmitted beam and a reflected beam, wherein the transmitted beam propagates along the original direction and the reflected beam is reflected by the beam splitter to propagate in a perpendicular direction. The phase shifter is positioned between the beam splitter and the movable mirror. The phase shifter is used to introduce a specific phase difference into the reflected beam, thereby enabling precise control over the formation and changes of the interference pattern. The transmitted beam and the reflected beam, after being reflected by the fixed mirror and the movable mirror respectively, coincide at the beam splitter, producing an interference effect.

[0013] Optionally, the movable reflector can be moved along the propagation direction of the transmitted light beam to change the optical path length.

[0014] Optionally, the device further includes an optical path adjustment system, including an arc guide rail, an incident optical path support, and an outgoing optical path support; The circular arc guide rail is located above the sample stage; the incident light path bracket is used to install the incident light path system; the exit light path bracket is used to install the exit light path system and the second harmonic self-coherent system. The incident light path support and the exit light path support can be slidably mounted on the arc guide rail, and can slide around the sample stage to adjust the incident light angle.

[0015] Optionally, the sample stage is provided with a motion module, which is used to move the sample under test in the x, y, and z directions, and rotate it 360 degrees around the axis with the normal direction of the xy plane as the axis, thereby changing the azimuth angle of the incident light.

[0016] The above embodiments of the present invention have the following beneficial effects: By setting up a second harmonic self-coherent system, the interface signal and volume signal generated by non-centrosymmetric materials can be effectively separated.

[0017] The difficulty in separating interface and volume signals stems from the fact that when a light beam penetrates the material under test, the nonlinear properties of the material generate second harmonics, which can reflect internal defect information. Specifically, defects at the material's interface and within its volume result in different second harmonic responses. Therefore, distinguishing between interface and volume signals is crucial for studying interface defects in symmetrical materials. Because the second harmonics at the material interface and in its volume share similar symmetry, traditional analytical methods struggle to differentiate them.

[0018] Based on this, the second harmonic self-coherent system of the present invention splits the light beam into a transmitted beam and a reflected beam. By adjusting the optical path difference and phase difference, interference light signals at different depths of the sample are obtained, thereby selectively extracting material interface signals and volume signals, thus solving the symmetry confusion problem and obtaining defect information inside the material. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1This is a schematic diagram of an embodiment of the second harmonic interface separation device based on self-coherence technology of the present invention; Figure 2 This is a schematic diagram of the structure of some embodiments of the second harmonic self-coherent system of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Circular arc guide rail; 2. Incident light path support; 3. Laser; 4. Half-wave plate; 5. First polarizer; 6. Filter; 7. Emitting objective lens; 8. Beam splitter; 9. Spot morphology analyzer; 10. Altimeter / observation lens; 11. Sample stage; 12. Probe objective lens; 13. Objective lens adjustment frame; 14. Beam adjuster; 15. Filter; 16. Beam splitter; 17. Phase shifter; 18. Movable mirror; 19. Fixed mirror; 20. Second polarizer; 21. Optical signal receiving device. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] Please see Figure 1 , Figure 1 This is a schematic diagram of an embodiment of the second harmonic interface separation device based on self-coherence technology of the present invention, as shown below. Figure 1 As shown, the second harmonic interface separation device based on self-coherence technology of the present invention includes an incident optical path system, a sample stage 11, an exit optical path system, and a second harmonic self-coherence system. The incident optical path system is used to control the polarization direction of the light beam and filter out stray light, so that the light beam is focused onto the sample placed on the sample stage 11; the exit optical path system is used to collimate and filter the light beam emitted from the sample; the second harmonic self-coherence system is used to split the light beam into a transmitted beam and a reflected beam, and after interference effect is generated, receive and analyze the optical signal.

[0027] The laser light passes through the incident optical path system and then illuminates the sample under test. Due to the nonlinear optical effects of the sample, the laser induces a second harmonic signal, which contains important information about the material's property parameters. When the second harmonic signal passes through the exit optical path system, it undergoes autocorrelation processing to enhance signal resolvability. The autocorrelated optical signal is then received by the optical signal receiving device 21 and analyzed through subsequent data processing. Finally, a detailed analysis of the material's properties is completed on a computer.

[0028] The incident optical path system includes a laser 3, a half-wave plate 4, a first polarizer 5, a filter 6, and an emitting objective lens 7. The beam emitted from the laser 3 has its polarization direction controlled by the half-wave plate 4. Then, it passes through the first polarizer 5, where its polarization characteristics are further enhanced. The polarization direction of the emitted beam from the first polarizer 5 is determined by the angle between its polarization direction and the fast axis of the half-wave plate 4. After passing through the filter 6, the beam is filtered to remove stray light of other wavelengths. Finally, it passes through the emitting objective lens 7, which focuses the beam onto the sample placed on the sample stage 11.

[0029] In some alternative embodiments, the incident light path system may further include a beam splitter 8 and a beam morphology analyzer 9. The beam splitter 8 is positioned between the focusing lens and the sample, such that the light beam is split into two paths after passing through the beam splitter 8. One beam is focused onto the sample, and the other beam is incident on the beam morphology analyzer 9. The beam morphology analyzer 9 is capable of analyzing the focal spot intensity distribution of the incident light beam and monitoring the morphology of the signal beam incident on the sample.

[0030] The samples described above are non-centrosymmetric materials, such as silicon carbide (SiC) wafers. The samples are placed on the sample stage 11, and a height measuring instrument / observation mirror 10 can be set above the sample stage 11 to obtain the height information of the sample being measured.

[0031] The outgoing optical path system, including a probe objective 12 and a filter 15, is used to receive the light beam emitted from the sample. The light beam emitted from the sample is received and collimated by the probe objective 12. The collimated light beam then passes through the filter 15, which removes the fundamental frequency light from the beam, retaining only the second harmonic, thereby providing a clean signal input for subsequent self-coherent analysis.

[0032] In some embodiments, the probe objective 12 can be mounted on the objective adjustment frame 13. A beam adjuster 14 is added between the probe objective 12 and the filter 15, allowing for fine adjustments to both the probe objective 12 and the emitted beam. The beam passing through the filter 15 enters the second harmonic self-coherent system.

[0033] Please see Figure 2 , Figure 2 These are schematic diagrams illustrating the structure of some embodiments of the second harmonic self-coherent system of the present invention. For example... Figure 2 As shown, the second harmonic self-coherent system includes a beam splitter 16, a fixed mirror 19, a movable mirror 18, a phase shifter 17, and a second polarizer 20. The light beam first passes through the beam splitter 16, which splits the incident beam into a transmitted beam and a reflected beam. The transmitted beam propagates along its original direction, while the reflected beam is reflected by the beam splitter 16 to propagate in a perpendicular direction. The transmitted beam and the reflected beam are then transmitted to the fixed mirror 19 and the movable mirror 18, respectively. Specifically, the fixed mirror 19 and the movable mirror 18 are located on opposite sides of the beam splitter 16, with the fixed mirror 19 on one side of the transmitted beam's optical path and the movable mirror 18 on the other side of the reflected beam's optical path.

[0034] A phase shifter 17 is positioned between the beam splitter 16 and the movable mirror 18. After the reflected beam passes through the phase shifter 17, the phase shifter 17 can introduce a specific phase difference, thereby enabling precise control over the formation and changes of the interference pattern. The movable mirror 18 can move back and forth along the propagation direction of the transmitted beam to change the optical path length.

[0035] The transmitted and reflected beams, after being reflected by the fixed mirror 19 and the movable mirror 18, coincide at the beam splitter 16. Due to the optical path difference, an interference effect occurs, thereby enhancing the resolvability of the optical signal. The interfered beam then passes through the second polarizer 20 to ensure a certain polarization state before entering the optical signal receiving device 21, such as a spectrometer or a single-photon counter. Finally, by analyzing the second harmonic signal acquired by the optical signal receiving device 21, detailed data on the optical properties of the sample can be obtained.

[0036] The second harmonic self-coherent system adjusts the optical path length using a movable mirror 18 and introduces a phase difference using a phase shifter 17, thereby controlling the optical path difference and phase difference of the beam. By adjusting the optical path length, it can match the optical path of reflected light from different depths of the sample, thus acquiring interference signals from different depths of the sample. This allows for the selective extraction of material interface signals and volume signals, resolving the symmetry confusion problem and obtaining information about defects within the material.

[0037] In some alternative implementations, the device may further include an optical path adjustment system, comprising an arc-shaped guide rail 1, an incident optical path support 2, and an exit optical path support. The arc-shaped guide rail 1 may be semi-circularly mounted on the sample stage 11. The incident optical path support 2 is used to mount the incident optical path system, and the exit optical path support is used to mount the exit optical path system and the second harmonic self-coherent system. The movable reflector 18 may be slidably mounted on the exit optical path support via a slide rail or similar device with a locking mechanism, with its sliding direction coinciding with the propagation direction of the transmitted beam.

[0038] The aforementioned incident light path support 2 and exit light path support are slidably mounted on the arc-shaped guide rail 1, allowing them to slide around the sample stage 11 located below, thereby controlling the incident light angle. As an example, two arc-shaped guide rail sliders can be installed on the arc-shaped guide rail 1, with the incident light path support 2 and exit light path support respectively mounted on them, allowing manual adjustment of the incident light angle. Alternatively, positioning bolts can be installed on the arc-shaped guide rail sliders; after adjusting the incident light angle, the positioning bolts can be tightened onto the arc-shaped guide rail to fix the incident light path support 2 and exit light path support.

[0039] As another example, two sliders can be installed on the arc-shaped guide rail 1, each slider having four rollers for clamping the two sides of the arc-shaped rail. Each roller is controlled by a motor, thereby enabling the slider to slide on the arc-shaped guide rail 1. The aforementioned incident light path bracket 2 and exit light path bracket are respectively installed on the sliders, and the incident angle of the light beam can be determined by controlling the stroke of the aforementioned motor.

[0040] In this way, by adjusting the incident light angle and combining the half-wave plate 4 and the first polarizer 5, the polarization direction can be adjusted, thus achieving multi-dimensional detection of azimuth angle, incident angle and polarization angle dependence.

[0041] In some optional implementations of the embodiments, the sample stage 11 is provided with a motion module, which enables the sample stage 11 and the material to be tested it carries to move in multiple dimensions, including movement in the x, y, and z directions, and 360-degree rotation with the xy plane normal direction as the axis, thereby changing the azimuth angle of the incident light. As an example, the motion module may be a multi-dimensional adjustment frame.

[0042] The circular arc guide rail 1 above the sample stage 11 can control the incident angle of the fundamental frequency light, and the polarizer group at the transmitting end can change the polarization angle of the fundamental frequency light. Therefore, through the cooperation of various components, this device can realize the detection of the dependence of azimuth, incident angle, and polarization angle in second harmonic characterization.

[0043] The second harmonic self-coherent system of this invention can effectively separate interface signals and volume signals generated by non-centrosymmetric material samples. When a light beam penetrates the material under test, second harmonics are generated due to the nonlinear characteristics of the material. These second harmonics can reflect the defect information inside the material. Specifically, interface defects and internal defects in the material will lead to different second harmonic responses. By controlling the optical path difference and phase difference of the light beam using the second harmonic self-coherent system of this invention, interference light signals at different depths of the sample can be obtained, thereby distinguishing interface signals and volume signals, which is crucial for studying interface defects in materials.

[0044] Furthermore, this invention can further improve the selectivity of the optical signal by changing the polarization direction of the laser, thereby not only improving the sensitivity and resolution of detection, but also enabling the detection of changes in the physical and chemical properties of the sample surface to a certain extent, providing more possibilities and application prospects for materials science and surface science research. With the advancement of laser technology and the improvement of second harmonic signal processing algorithms, these technologies also have broad potential in industrial applications. For example, in the manufacturing of optoelectronic devices, second harmonic technology can be used to accurately evaluate the optical properties and electronic structure of materials, providing crucial data support for the design and optimization of novel devices.

[0045] Overall, second harmonic generation technology, with its efficient and accurate characterization capabilities, will continue to play an important role in materials science, optical engineering, and surface physics research.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A second harmonic interface separation device based on self-coherent technology, characterized in that, include: An incident light path system is used to control the polarization direction of the light beam and filter out stray light so that the light beam is focused onto the sample placed on the sample stage, wherein the sample is a non-centrosymmetric material. The outgoing optical path system is used to collimate and filter the light beam emitted from the sample. The second harmonic self-coherent system is used to split a light beam into a transmitted beam and a reflected beam that can produce an interference effect. By adjusting the optical path difference and phase difference of the beam, the interface signal and volume signal of the sample can be selectively extracted.

2. The second harmonic interface separation device based on self-coherence technology according to claim 1, characterized in that, The incident optical path system includes a laser, a half-wave plate, a first polarizer, a filter, and an emission objective lens; The half-wave plate is used to control the polarization direction of the beam; the first polarizer is used to further enhance the polarization characteristics of the beam; the filter is used to filter the beam; and the emission objective is used to focus the beam onto the sample.

3. The second harmonic interface separation device based on self-coherence technology according to claim 2, characterized in that, The incident optical path system also includes a beam splitter and a spot morphology analyzer; The beam splitter is positioned between the focusing lens and the sample, so that the light beam is split into two paths after passing through the beam splitter. One beam is focused onto the sample, and the other beam is incident on the spot morphology analyzer. The beam spot morphology analyzer is used to analyze the focal spot intensity distribution of the incident beam and monitor the morphology of the signal beam incident on the sample.

4. The second harmonic interface separation device based on self-coherence technology according to claim 1, characterized in that, A height measuring instrument / observation mirror is also installed above the sample stage to obtain the height information of the sample being tested.

5. The second harmonic interface separation device based on self-coherence technology according to claim 1, characterized in that, The outgoing optical path system is used to receive the light beam emitted from the sample, and includes a detector objective and a filter; The detection objective lens is used to collimate the outgoing light beam; the filter is used to remove the fundamental frequency light from the collimated light beam while retaining the second harmonic.

6. The second harmonic interface separation device based on self-coherence technology according to claim 5, characterized in that, The output optical path system also includes an objective lens adjustment frame and a beam adjuster. The probe objective lens is mounted on the objective lens adjustment frame for fine-tuning the probe objective lens; the beam adjuster is positioned between the probe objective lens and the filter for fine-tuning the output beam.

7. The second harmonic interface separation device based on self-coherence technology according to claim 1, characterized in that, The second harmonic self-coherent system includes a beam splitter, a fixed mirror, a movable mirror, a phase shifter, and a second polarizer. The beam splitter is used to split the incident beam into a transmitted beam and a reflected beam, wherein the transmitted beam propagates along the original direction and the reflected beam is reflected by the beam splitter to propagate in a perpendicular direction. The phase shifter is positioned between the beam splitter and the movable mirror. The phase shifter is used to introduce a specific phase difference into the reflected beam, thereby enabling precise control over the formation and changes of the interference pattern. The transmitted beam and the reflected beam, after being reflected by the fixed mirror and the movable mirror respectively, coincide at the beam splitter, producing an interference effect.

8. The second harmonic interface separation device based on self-coherence technology according to claim 7, characterized in that, The movable reflector can move along the propagation direction of the transmitted light beam to change the optical path length.

9. The second harmonic interface separation device based on self-coherence technology according to any one of claims 1-7, characterized in that, The device also includes an optical path adjustment system, comprising an arc guide rail, an incident optical path support, and an outgoing optical path support; The circular arc guide rail is located above the sample stage; the incident light path bracket is used to install the incident light path system; the exit light path bracket is used to install the exit light path system and the second harmonic self-coherent system. The incident light path support and the exit light path support can be slidably mounted on the arc guide rail, and can slide around the sample stage to adjust the incident light angle.

10. The second harmonic interface separation device based on self-coherence technology according to claim 9, characterized in that, The sample stage is equipped with a motion module, which is used to move the sample under test in the x, y, and z directions, and rotate it 360 degrees around the axis with the normal direction of the xy plane as the axis, thereby changing the azimuth angle of the incident light.

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