Transmission-type second harmonic characteristic testing device and testing method

Abstract

The invention discloses a transmission-type second harmonic characteristic testing device. A light source module (1) generates pumping laser; the light path adjusting module (2) is used for adjusting and controlling the power and the polarization state of the pumping laser generated by the light source module (1); a to-be-tested sample (14) is fixed in the transmission-type sample chamber (3), and the pumping laser is focused on the to-be-tested sample (14) and generates a second harmonic signal; the detection module (4) extracts and receives the second harmonic signal and detects the strength of the second harmonic signal; and the data processing device (5) processes the intensity of the received second harmonic signal, records the change of the intensity of the second harmonic signal along with time, performs average processing, and finally displays test data and results. The invention further discloses a transmission-type second harmonic characteristic testing method. The device is simple and practical, can test the optical parameters such as the second harmonic spectrum and the light intensity of the two-dimensional material, improves the test efficiency, and is convenient to popularize and apply.

Description

Technical Field

[0001] The invention belongs to the technical field of nonlinear optics and relates to a transmission type second harmonic characteristic testing device and a testing method. Background Art

[0002] The discovery of the second harmonic phenomenon in quartz crystals in 1961 opened up another major branch of the field of optics: nonlinear optics. Nonlinear optics mainly studies the nonlinear interaction between light and matter, and is widely used in the field of optoelectronic technology. Second harmonic generation (SHG) is an important component of nonlinear optics. Its process can be expressed as two photons with a frequency of ω interacting with the medium to produce a photon with a frequency of 2ω. Second harmonics have great application potential in the fields of nonlinear optical frequency doubling, optical modulation, detection and microscopic imaging. For example, the green and blue-violet lasers commonly used in laboratories and industry are often obtained by frequency doubling the near-infrared light generated by laser crystals such as Nd:YAG; and to achieve laser output with continuously adjustable wavelength, it is necessary to combine multiple nonlinear optical effects such as sum frequency, difference frequency, and cascaded second harmonics. For optical detection and imaging, the spatial resolution directly depends on the wavelength of the light source used. Through these nonlinear optical effects, people can convert long-wavelength light sources into shorter-wavelength detection light to improve the resolution of detection and imaging. As one of the most basic nonlinear optical effects, second harmonic has played an important role in actual production and life, and is also a key research topic in the field of optics.

[0003] Two-dimensional materials are currently a hot topic in the research of nonlinear optical materials. Due to the spatial asymmetry of the crystal structure, even a single layer of two-dimensional materials can produce a strong second harmonic effect, including molybdenum disulfide, molybdenum ditelluride, tungsten diselenide, etc. Researchers can adjust the second harmonic signal intensity by adjusting the thickness of the material and the stress on the material. In addition, the thickness of the material at the nanoscale can effectively control the size of the device. The intrinsic film surface is smooth and has no dangling bonds, and can be attached to a variety of substrates. The above properties make two-dimensional materials applicable to miniaturized nonlinear optical integrated devices.

[0004] The second harmonic characteristics test of a material can determine its nonlinear optical properties, but due to the small surface area of ​​two-dimensional materials (nanometer or micrometer level), the requirements for the focusing of the incident laser beam are relatively strict. Existing commercial testing devices are all implemented through a reflective laser confocal microscopy system, which uses laser to excite the material to be tested, and uses a detector to detect the second harmonic signal generated by the reflected sample to analyze the second harmonic characteristics of the sample. This device is more suitable for the study of surface properties, with a complex structure, high price, and weak test signals. Two-dimensional materials are thin and transparent. For the application of two-dimensional materials in the field of nonlinear optics, it is more desirable to obtain the properties of the material as a whole or in the internal area, and to improve the test efficiency. Summary of the invention

[0005] (I) Purpose of the invention

[0006] The purpose of the present invention is to provide a transmission-type second harmonic characteristic testing device and testing method which has a simple structure, is easy to build, simple to operate, and can test the second harmonic characteristics of the entire two-dimensional material in order to address the shortcomings of the above-mentioned existing testing devices.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a transmission type second harmonic characteristic testing device, which comprises a light source module 1, an optical path adjustment module 2, a transmission type sample chamber 3 and a detection module 4 which are sequentially arranged along the optical path direction, and a data processing device 5 connected to the detection module 4; the light source module 1 generates a pump laser; the optical path adjustment module 2 adjusts and controls the power and polarization state of the pump laser generated by the light source module 1; a sample 14 to be tested is fixed in the transmission type sample chamber 3, the pump laser is focused on the sample 14 to be tested and generates a second harmonic signal; the detection module 4 extracts and receives the second harmonic signal, and detects the intensity of the second harmonic signal; the data processing device 5 processes the intensity of the received second harmonic signal, records the change of the intensity of the second harmonic signal over time, performs average processing, and finally displays the test data and results.

[0009] The light source module 1 includes a laser 6 and an optical isolator 7 arranged on the light output side of the laser 6; the laser 6 is used to generate a pump laser; the optical isolator 7 is placed at the right end of the laser 6 to prevent reflected light or scattered light of the laser from entering the laser 6.

[0010] Wherein, the optical path adjustment module 2 includes an aperture 8 and a polarization control unit 9; the aperture 8 is placed between the optical isolator 7 and the polarization control unit 9, and is used to limit the diameter of the pump laser beam and exclude stray light; the polarization control unit 9 includes two half-wave plates 10 and a polarization beam splitter 11 located between the two half-wave plates 10, and is used to control the power and polarization state of the pump laser.

[0011] The transmission sample chamber 3 includes a sample stage 12 with a sample fixture and a lens group 13; the lens group 13 includes a pair of lenses, the sample stage 12 with a sample fixture is placed between a pair of lenses of the lens group 13, and the sample 14 to be tested is arranged on the sample stage 12 with the sample fixture. The lens group 13 is used to focus the pump laser onto the sample 14 to be tested and collect the generated second harmonic signal.

[0012] The sample stage 12 with the sample fixture has translation and rotation functions, and is used to adjust the position and angle of the sample 14 to be tested.

[0013] The sample 14 to be tested is first placed on a transparent base material, and then placed together with the transparent base material on a sample stage 12 with a sample fixture.

[0014] The detection module 4 includes a beam splitter 15 , a CCD optical camera 16 located on the reflective side of the beam splitter 15 , a filter 17 located on the transparent side of the beam splitter 15 , and an optical testing instrument 18 , which are used to test the second harmonic signal generated by the sample 14 to be tested.

[0015] Among them, the beam splitter 15 is placed after the lens group 13, and is used to separate the pump laser from the second harmonic signal; the CCD optical camera 16 is placed in the pump laser light path after being separated by the beam splitter 15, and is used to amplify and observe the surface of the sample to be tested 14 to ensure that the incident pump laser is irradiated on the surface of the sample to be tested 14; the filter 17 is arranged in the second harmonic signal light path after being separated by the beam splitter 15, and is used to filter out noise and extract the second harmonic signal; the optical testing instrument 18 is placed at the right end of the filter 17, and is used to receive the second harmonic signal and detect the intensity of the second harmonic signal.

[0016] The data processing device 5 includes a computer system 19 and a display 20. The computer system 19 runs data analysis software to process the received second harmonic signal intensity, record the change of the second harmonic signal intensity over time, and perform average processing; the display 20 displays the test data and results.

[0017] The present invention also provides a transmission type second harmonic characteristic testing method, which comprises the following steps:

[0018] Step 1: Sample preparation

[0019] Clean the surface of the prepared sample 14 with anhydrous ethanol and acetone solution, place the sample 14 on the transparent substrate material, and then fix it together with the transparent substrate material on the sample stage 12 with a sample fixture, and adjust the position of the sample 14 so that the surface of the sample 14 is perpendicular to the propagation direction of the pump laser beam;

[0020] Step 2: Light source settings

[0021] Select laser 6 as the pump laser source, turn on the power of laser 6 and adjust it to the set power;

[0022] Step 3: Adjust the optical path

[0023] Use a beam splitter 15 to separate the pump laser and the second harmonic signal light, use a CCD optical camera 16 to observe the surface of the sample 14 to be tested, adjust the position of the sample 14 to ensure that the incident laser is perpendicular to the surface of the sample 14; use a lens group 13 to focus the pump laser onto the sample 14 to be tested, and adjust the position of the lens group 13 to obtain the best focusing effect;

[0024] Step 4: Signal processing and data acquisition analysis

[0025] The generated second harmonic signal is filtered by a filter 17 to remove noise and interference; the filtered second harmonic signal is received by an optical testing instrument 18, and the spectral response range of the optical testing instrument 18 covers the wavelength of the second harmonic signal; the optical testing instrument 18 transmits the second harmonic signal to a computer system 19, runs data analysis software, records the change of the intensity of the second harmonic signal over time, and performs average processing;

[0026] Step 5: Polarization test and result output

[0027] Adjust the pump laser power, analyze the relationship between the second harmonic signal intensity and the pump laser power, and determine the efficiency of second harmonic generation; change the pump laser polarization state, collect the second harmonic signal of the sample to be tested under different laser polarization states, analyze the second harmonic characteristics of the sample to be tested and the pump laser polarization state, and output the test results; present the test results in the form of charts.

[0028] (III) Beneficial effects

[0029] The transmission second harmonic characteristic test device and test method provided by the above technical solution are simple and practical, and can realize the test of the second harmonic spectrum, light intensity and other optical parameters of two-dimensional materials, thereby improving the test efficiency and facilitating promotion and application; the test results are accurate and reliable, which is helpful for in-depth research on the nonlinear optical properties of two-dimensional materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of the transmission type second harmonic characteristic testing device designed for the present invention.

[0031] Figure 2 Flow chart of the transmission-type second harmonic characteristic testing method designed for the present invention.

[0032] Figure 3is the polarization dependence curve of the second harmonic signal.

[0033] Explanation of the reference numerals in the figure: light source module 1, optical path adjustment module 2, transmission sample chamber 3, detection module 4, data processing device 5, laser 6, isolator 7, aperture 8, polarization control unit 9, half-wave plate 10, polarization beam splitter 11, sample stage with sample fixture 12, lens group 13, sample to be tested 14, beam splitter 15, CCD optical camera 16, filter 17, optical testing instrument 18, computer system 19, display 20. DETAILED DESCRIPTION

[0034] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0035] like Figure 1 As shown, the transmission type second harmonic characteristic testing device of this embodiment includes a light source module 1, a light path adjustment module 2, a transmission type sample chamber 3 and a detection module 4 which are sequentially arranged along the light path direction, and a data processing device 5 connected to the detection module 4; the light source module 1 generates a pump laser; the light path adjustment module 2 adjusts and controls the power and polarization state of the pump laser generated by the light source module 1; a sample 14 to be tested is fixed in the transmission type sample chamber 3, the pump laser is focused on the sample 14 to be tested and generates a second harmonic signal; the detection module 4 extracts and receives the second harmonic signal, and detects the intensity of the second harmonic signal; the data processing device 5 processes the intensity of the received second harmonic signal, records the change of the intensity of the second harmonic signal over time, performs average processing, and finally displays the test data and results.

[0036] The light source module 1 includes a laser 6 and an optical isolator 7 arranged on the light-emitting side of the laser 6; the laser 6 is used to generate a pump laser; the optical isolator 7 is placed at the right end of the laser 6 to prevent reflected light or scattered light of the laser from entering the laser 6, thereby protecting the laser 6 from damage.

[0037] The optical path adjustment module 2 includes an aperture 8 and a polarization control unit 9; the aperture 8 is placed between the optical isolator 7 and the polarization control unit 9, and is used to limit the diameter of the pump laser beam and exclude stray light; the polarization control unit 9 includes two half-wave plates 10 and a polarization beam splitter 11 located between the two half-wave plates 10, and is used to control the power and polarization state of the pump laser to optimize the generation efficiency of the second harmonic.

[0038] The transmission sample chamber 3 is used to fix the sample to be tested, and includes a sample stage 12 with a sample fixture and a lens group 13; the lens group 13 includes a pair of lenses, the sample stage 12 with the sample fixture is placed between the pair of lenses of the lens group 13, and the sample to be tested 14 is arranged on the sample stage 12 with the sample fixture. The lens group 13 is used to focus the pump laser onto the sample to be tested 14 and collect the generated second harmonic signal.

[0039] The sample stage 12 with the sample fixture has translation and rotation functions, and is used to adjust the position and angle of the sample 14 to be tested, and can ensure that the sample 14 to be tested is stable and motionless during the test process.

[0040] The sample 14 to be tested is first placed on a transparent base material, and then placed together with the transparent base material on a sample stage 12 with a sample fixture.

[0041] The detection module 4 includes a beam splitter 15 , a CCD optical camera 16 located on the reflective side of the beam splitter 15 , a filter 17 located on the transparent side of the beam splitter 15 , and an optical testing instrument 18 , which is used to test the second harmonic signal generated by the sample 14 to be tested.

[0042] Among them, the beam splitter 15 is placed after the lens group 13, and is used to separate the pump laser from the second harmonic signal to prevent the pump laser from directly entering the optical testing instrument 18; the CCD optical camera 16 is placed in the pump laser light path after being separated by the beam splitter 15, and is used to magnify and observe the surface of the sample to be tested 14, while ensuring that the incident pump laser is irradiated on the surface of the sample to be tested 14; wherein the filter 17 is arranged in the second harmonic signal light path after being separated by the beam splitter 15, and is used to filter out noise and extract the second harmonic signal; the optical testing instrument 18 is placed at the right end of the filter 17, and is used to receive the second harmonic signal and detect the intensity of the second harmonic signal.

[0043] The data processing device 5 includes a computer system 19 and a display 20, which are used to run data analysis software, process the received second harmonic signal intensity, record the change of the second harmonic signal intensity over time, perform average processing, and finally display the test data and results.

[0044] like Figure 2 As shown, the transmission type second harmonic characteristic testing method of this embodiment includes the following steps:

[0045] Step 1: Sample preparation

[0046] Clean the surface of the prepared sample 14 with anhydrous ethanol and acetone solution to ensure that there is no dust, oil or other impurities to avoid affecting the transmission of light and the generation of the second harmonic signal; then place the sample 14 on the transparent substrate material, and then fix it together with the transparent substrate material on the sample stage 12 with a sample fixture, and adjust the position of the sample 14 to make the surface of the sample 14 perpendicular to the propagation direction of the pump laser beam;

[0047] Step 2: Light source settings

[0048] Select laser 6 as the pump laser source, turn on the power of laser 6 and adjust it to the set power to ensure that the output of laser 6 is stable, without mode hopping or other fluctuations, and also ensure that the sample 14 to be tested is not damaged due to excessive power;

[0049] Step 3: Adjust the optical path

[0050] Use a beam splitter 15 to separate the pump laser and the second harmonic signal light, use a CCD optical camera 16 to observe the surface of the sample 14 to be tested, adjust the position of the sample 14 to ensure that the incident laser is perpendicular to the surface of the sample 14 to be tested; use a lens group 13 to focus the pump laser onto the sample to be tested, and adjust the position of the lens group 13 to obtain the best focusing effect;

[0051] Step 4: Signal processing and data acquisition analysis

[0052] The generated second harmonic signal is filtered by a filter 17 to remove noise and interference and improve the quality of the second harmonic signal; the processed second harmonic signal is received by an optical testing instrument 18 to ensure that the spectral response range of the optical testing instrument 18 covers the wavelength of the second harmonic signal; then the optical testing instrument 18 transmits the second harmonic signal to a computer system 19, runs data analysis software, records the intensity change of the second harmonic signal over time, and performs average processing to reduce random errors;

[0053] Step 5: Polarization test and result output

[0054] Adjust the pump laser power and analyze the relationship between the second harmonic signal intensity and the pump laser power to determine the efficiency of second harmonic generation; change the pump laser polarization state, collect the second harmonic signal of the sample to be tested under different laser polarization states, analyze the second harmonic characteristics of the sample to be tested and the pump laser polarization state, and output the test results; present the test results in the form of charts for further analysis and research.

[0055] The test device and test method of this embodiment can be used to test the second harmonic characteristics of the two-dimensional material SnS2P6, such as Figure 3 As shown, it is the polarization dependence curve of the second harmonic signal of the material, where θ is the polarization change angle.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A transmission type second harmonic characteristic testing device, characterized in that: The invention comprises a light source module (1), a light path adjustment module (2), a transmission sample chamber (3) and a detection module (4) which are sequentially arranged along the light path direction, and a data processing device (5) connected to the detection module (4); the light source module (1) generates pump laser; the light path adjustment module (2) adjusts and controls the power and polarization state of the pump laser generated by the light source module (1); a sample to be tested (14) is fixed in the transmission sample chamber (3), the pump laser is focused on the sample to be tested (14) and generates a second harmonic signal; the detection module (4) extracts and receives the second harmonic signal and detects the intensity of the second harmonic signal; the data processing device (5) processes the intensity of the received second harmonic signal, records the change of the intensity of the second harmonic signal over time, performs average processing, and finally displays the test data and results.

2. The transmission type second harmonic characteristic testing device according to claim 1, characterized in that: The light source module (1) comprises a laser (6) and an optical isolator (7) arranged on the light output side of the laser (6); the laser (6) is used to generate pump laser light; the optical isolator (7) is placed at the right end of the laser (6) and is used to prevent reflected light or scattered light of the laser from entering the laser (6).

3. The transmission type second harmonic characteristic testing device according to claim 2, characterized in that: The optical path adjustment module (2) comprises an aperture (8) and a polarization control unit (9); the aperture (8) is placed between the optical isolator (7) and the polarization control unit (9) and is used to limit the diameter of the pump laser beam and exclude stray light; the polarization control unit (9) comprises two half-wave plates (10) and a polarization beam splitter (11) located between the two half-wave plates (10) and is used to control the power and polarization state of the pump laser.

4. The transmission type second harmonic characteristic testing device according to claim 3, characterized in that: The transmission type sample chamber (3) comprises a sample stage (12) with a sample fixture and a lens group (13); the lens group (13) comprises a pair of lenses, the sample stage (12) with the sample fixture is placed between the pair of lenses of the lens group (13), the sample to be tested (14) is arranged on the sample stage (12) with the sample fixture, and the lens group (13) is used to focus the pump laser onto the sample to be tested (14) and collect the generated second harmonic signal.

5. The transmission type second harmonic characteristic testing device according to claim 4, characterized in that: The sample stage (12) with the sample fixture has translation and rotation functions and is used to adjust the position and angle of the sample (14) to be tested.

6. The transmission type second harmonic characteristic testing device according to claim 4, characterized in that: The sample to be tested (14) is first placed on a transparent base material, and then placed together with the transparent base material on a sample table (12) with a sample fixture.

7. The transmission type second harmonic characteristic testing device according to claim 4, characterized in that: The detection module (4) comprises a beam splitter (15), a CCD optical camera (16) located on the reflective side of the beam splitter (15), a filter (17) located on the transparent side of the beam splitter (15), and an optical testing instrument (18), and is used to test the second harmonic signal generated by the sample to be tested (14).

8. The transmission type second harmonic characteristic testing device according to claim 7, characterized in that: The beam splitter (15) is placed after the lens group (13) and is used to separate the pump laser from the second harmonic signal; the CCD optical camera (16) is placed in the pump laser light path after being separated by the beam splitter (15) and is used to magnify and observe the surface of the sample to be tested (14) to ensure that the incident pump laser irradiates the surface of the sample to be tested (14); the filter (17) is arranged in the second harmonic signal light path after being separated by the beam splitter (15) and is used to filter out noise and extract the second harmonic signal; the optical testing instrument (18) is placed at the right end of the filter (17) and is used to receive the second harmonic signal and detect the intensity of the second harmonic signal.

9. The transmission type second harmonic characteristic testing device according to claim 8, characterized in that: The data processing device (5) comprises a computer system (19) and a display (20); the computer system (19) runs data analysis software, processes the intensity of the received second harmonic signal, records the change of the intensity of the second harmonic signal over time, and performs average processing; the display (20) displays the test data and results.

10. A transmission type second harmonic characteristic testing method based on the testing device according to claim 9, characterized in that: The following steps are involved: Step 1: Sample preparation Cleaning the surface of the prepared sample (14) to be tested with anhydrous ethanol and acetone solution, placing the sample (14) to be tested on a transparent substrate material, and then fixing the sample (14) and the transparent substrate material on a sample stage (12) with a sample fixture, and adjusting the position of the sample (14) to be tested so that the surface of the sample (14) to be tested is perpendicular to the propagation direction of the pump laser beam; Step 2: Light source settings Selecting a laser (6) as a pump laser source, turning on the power of the laser (6) and adjusting it to a set power; Step 3: Adjust the optical path A beam splitter (15) is used to separate the pump laser and the second harmonic signal light, a CCD optical camera (16) is used to observe the surface of the sample to be tested (14), and the position of the sample to be tested (14) is adjusted to ensure that the incident laser is perpendicularly incident on the surface of the sample to be tested (14); a lens group (13) is used to focus the pump laser onto the sample to be tested (14), and the position of the lens group (13) is adjusted to obtain the best focusing effect; Step 4: Signal processing and data acquisition analysis The generated second harmonic signal is filtered using a filter (17) to remove noise and interference; the filtered second harmonic signal is received by an optical testing instrument (18), and the spectral response range of the optical testing instrument (18) covers the wavelength of the second harmonic signal; the optical testing instrument (18) transmits the second harmonic signal to a computer system (19), runs data analysis software, records the change of the intensity of the second harmonic signal over time, and performs average processing; Step 5: Polarization test and result output Adjust the pump laser power, analyze the relationship between the second harmonic signal intensity and the pump laser power, and determine the efficiency of second harmonic generation; change the pump laser polarization state, collect the second harmonic signal of the sample to be tested under different laser polarization states, analyze the second harmonic characteristics of the sample to be tested and the pump laser polarization state, and output the test results; present the test results in the form of charts.

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