A laser plasma three-wavelength interference diagnostic device and its adjustment method

Abstract

The present invention discloses a laser plasma three-wavelength interference diagnostic device and an adjustment method thereof. The device includes a detection light source system, a plasma excitation system, a detection optical path system and a receiving system. The laser plasma generated by the laser excitation device is placed in the detection optical path of the Mach-Zehnder interferometer. The white pulse light source generated by the detection light source device is used as the detection light. The Mach-Zehnder interferometer divides the detection light into two beams, one beam passes through the laser plasma area, and the other beam is used as a reference light. The two beams meet after passing through the Mach-Zehnder interferometer. The receiving system includes an RGB filter grating and a color CCD. The light after meeting is divided into three beams of light with different wavelengths through the RGB filter grating to form three interference fringe patterns. The device can simultaneously obtain three interference fringe patterns carrying laser plasma phase information, obtain more data graphs, and make the results more accurate, effective and comprehensive.

Description

Technical Field

[0001] The invention belongs to the technical field of laser plasma diagnosis, relates to laser plasma parameter diagnosis technology, and particularly to a laser plasma three-wavelength interference diagnosis device and an adjustment method thereof. Background Art

[0002] The diagnostic technology of laser plasma mainly diagnoses plasma parameters such as plasma temperature, plasma density, electron energy distribution function, ion energy, various ions and excited groups, etc. They affect the physical and chemical processes of the interaction between plasma and materials and determine the structure and properties of the final material. At present, the more commonly used diagnostic technologies can be divided into two categories: off-site technology and in-situ technology. The off-site technology is to extract the plasma sample from the reactor and then detect it with instruments, mainly electron paramagnetic resonance. In-situ technology includes invasive and non-invasive methods. Invasive diagnostic technology disturbs the plasma, such as Langmuir probe technology; non-invasive diagnostic technology is divided into interference diagnosis and non-interference diagnosis. Non-interference detection includes optical shadow method, schlieren method, high-speed photography method, spectroscopy method, etc.

[0003] Among the existing diagnostic technologies, laser interferometry has nanosecond time resolution and micron spatial resolution. It can observe the fine structure inside the plasma and obtain rich parameters such as plasma electron density, electron temperature, diffusion velocity, and plasma morphology. Based on the axisymmetric distribution of the plasma, it can also obtain the three-dimensional distribution of plasma electron density. It is a powerful means of diagnosing plasma. The laser interferometry diagnostic method mainly uses the change in refractive index caused by the detection beam passing through the flow field and the absorption of the plasma to reflect the properties of the plasma field. The parameters such as electron density, ionization degree, temperature and pressure in the plasma and their distribution can be calculated from the offset of the interference fringes. This method can obtain the distribution of the entire field through a single exposure and can reproduce the transient development and change process of the laser plasma. However, the current laser interferometry diagnostic technology system has strong signal interference, and it is necessary to further improve the interference system, reduce system noise, filter out signal disturbances, and improve the resolution of the laser interferometry diagnostic system. Summary of the invention

[0004] The purpose of the present invention is to provide a laser plasma three-wavelength interference diagnostic device and an adjustment method thereof, so as to improve the quality of the interference fringe pattern carrying the laser plasma phase information through three-wavelength interference, thereby improving the measurement accuracy of the laser plasma parameters.

[0005] The technical purpose of the present invention is achieved through the following technical solutions:

[0006] A laser plasma three-wavelength interference diagnostic device is composed of a detection light source system, a laser plasma excitation system, an interference optical path system and a receiving system.

[0007] Preferably, the detection light source system includes a first laser, a first focusing lens, a concave reflector and a second focusing lens. The first focusing lens is located along the direction of the laser light source output by the first laser. In the vertical direction of the laser beam output by the first laser, from left to right are the concave reflector, the laser plasma generated by the laser penetrating the air through the focusing lens, and the second focusing lens. The focal points of the first focusing lens, the concave reflector and the second focusing lens are located at the same position. The laser is focused in the air through the focusing lens, causing optical breakdown in the focal area to generate laser plasma, which is accompanied by the generated white flash as the detection light source and enters the interference light path system through the second focusing lens.

[0008] Preferably, the laser plasma excitation system consists of a second laser and a third focusing lens. The third focusing lens is located along the direction of the laser light source output by the second laser. The second laser is focused on a focal point by the third focusing lens. The generated laser plasma serves as the laser plasma to be measured, wherein a focal point of the third focusing lens is located in the measuring optical path where the first plane beam splitter and the first plane reflector are located.

[0009] Preferably, the interference optical path system is a Mach-Zehnder interferometer composed of a first plane beam splitter, a first plane reflector, a second plane beam splitter and a second plane reflector. The laser plasma to be measured is located in the measurement optical path where the first plane beam splitter and the first plane reflector are located. The detection light source is divided into two beams of light through the first plane beam splitter, one beam of light passes through the laser plasma to be measured, the first plane reflector and the second plane beam splitter as measurement light; the other beam of light passes through the second plane reflector and the second plane beam splitter as reference light. The reference light and the measurement light meet again after passing through the second plane beam splitter, and are combined into a beam of light to enter the receiving system.

[0010] Preferably, the receiving system is composed of a fourth focusing lens, an RGB filter aperture, and a color CCD. The light from the interference optical path system passes through the fourth focusing lens and the RGB filter aperture to form three coherent light beams carrying the laser plasma phase information, and then the three coherent light beams enter the color CCD, which is connected to a computer to display the interference fringe image in real time.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. The device of the present application can be applied to laser plasma interference diagnosis technology, and can obtain interference images carrying laser plasma phase information. The device uses a white pulse light source as a detection light source. After passing through the interference system and the RGB filter aperture, three interference images carrying laser plasma phase information can be formed at the same time, and more data images can be obtained, making the results more accurate, effective and comprehensive.

[0013] 2. The traditional laser plasma interference device has strong system noise, while the present device uses the white flash generated by the laser plasma generation process as the detection light source, effectively avoiding the light source noise when the laser is used as the detection light source in the traditional interference device. The RGB filter aperture in the receiving system is filtered to effectively eliminate the influence of the surrounding environment noise;

[0014] 3. The device of the present application has a simple structure, a wide range of applications, and high adjustability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the detection light source system device of the present invention, wherein 1 is a first laser, 2 is a first focusing lens, 3 is a concave reflector, and 4 is a second focusing lens.

[0016] Figure 2 5 is a schematic diagram of the overall structure of the laser plasma three-wavelength interference diagnostic device of the present invention. Figure 1 The detection light source generated by the detection light source system device, 6 is the second laser, 7 is the third focusing lens, P1 and P2 are the first plane beam splitter and the second plane beam splitter respectively, M1 and M2 are the first plane reflector and the second plane reflector respectively, 8 is the fourth focusing lens, 9 is the RGB filter aperture, and 10 is the color CCD. DETAILED DESCRIPTION

[0017] The specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings and examples:

[0018] A laser plasma three-wavelength interference diagnostic device, comprising a detection light source system, a laser plasma excitation system, an interference optical path system and a receiving system, wherein the detection light source system is used to generate a detection light source, the laser plasma excitation system is used to generate a laser plasma to be tested, the interference optical path system is used to receive the detection light source, and the receiving system is used to generate three coherent light beams carrying laser plasma phase information;

[0019] The interference optical path system includes a first plane beam splitter P1, a first plane reflector M1, a second plane beam splitter P2 and a second plane reflector M2. The detection light source is divided into two beams by the first plane beam splitter P1, one beam passes through the laser plasma to be measured, the first plane reflector M1 and the second plane beam splitter P2 as the measurement light; the other beam passes through the second plane reflector M2 and the second plane beam splitter P2 as the reference light. The reference light and the measurement light meet again after passing through the second plane beam splitter P2, and are combined into a beam of light to enter the receiving system;

[0020] The receiving system includes a fourth focusing lens 8, an RGB filter aperture 9, and a color CCD 10. The light from the interference optical path system passes through the fourth focusing lens 8 and the RGB filter aperture 9 to form three coherent light beams carrying laser plasma phase information. Then the three coherent light beams enter the color CCD 10. The color CCD is connected to a computer to display the interference fringe image in real time.

[0021] Furthermore, the detection light source system includes a first laser 1, a first focusing lens 2, a concave reflecting mirror 3 and a second focusing lens 4. The focal points of the first focusing lens 2, the concave reflecting mirror 3 and the second focusing lens 4 are located at the same position. The first focusing lens 2 is along the direction of the laser light source output by the first laser 1. In the vertical direction of the laser beam output by the first laser 1, from left to right are the concave reflecting mirror 3, the laser breaks through the air through the first focusing lens 2 to generate laser plasma, and the second focusing lens 4. The laser emitted by the first laser 1 is focused in the air through the first focusing lens 2, causing optical breakdown in the focal area to generate laser plasma, and the white flash generated as the detection light source passes through the second focusing lens 4 into the interference optical path system.

[0022] Furthermore, the laser plasma excitation system includes a second laser 6 and a third focusing lens 7. The second laser 6 is focused in the air through the third focusing lens 7 to induce air breakdown, and the formed laser plasma serves as the laser plasma to be measured.

[0023] The adjustment method of the laser plasma three-wavelength interference diagnostic device is:

[0024] (1) Adjust the interference optical path system, first place the first plane beam splitter P1 to obtain two strictly perpendicular sub-beams; place the first plane reflector M1 to obtain two strictly parallel sub-beams of equal height; place the second plane reflector M2 to obtain the intersection position of the beams with strictly equal optical path in space; place the second plane beam splitter P2 at the intersection of the beams with equal optical path in the previous step.

[0025] (2) Adjust the detection light source system, such as Figure 1As shown, 1 is the first laser, 2 is the first focusing lens, 3 is the concave reflector, and 4 is the second focusing lens, wherein the focal points of the first focusing lens, the concave reflector, and the second focusing lens are located at the same point. The laser is focused in the air through the lens, causing optical breakdown in the focal area, generating laser plasma, and the generated white flash as a detection light source passes through the second focusing lens into the interference optical path system adjusted in step (1).

[0026] (3) Adjusting the laser plasma excitation system, such as Figure 2 As shown, 6 is the second laser, 7 is the third focusing lens, the second laser is focused in the air through the third focusing lens, and the generated laser plasma is used as the laser plasma to be measured, wherein a focus of the third focusing lens is located in the P1-M1 optical path of the interference system adjusted in step (1).

[0027] (4) Adjust the receiving system, such as Figure 2 As shown, 8 is a fourth focusing lens, 9 is an RGB filter aperture, and 10 is a color CCD, wherein the fourth focusing lens, the RGB filter aperture, and the color CCD are on the same horizontal line.

[0028] In this embodiment, laser 1 and laser 6 are Q-switched Nd:YAG lasers with an output wavelength of 1064 nm, a pulse width of 7 ns, and a maximum effective single pulse energy of 600 mJ. The laser 1 is focused in the air through the lens 2, causing optical breakdown in the focal area to generate laser plasma, and the generated white flash is used as a detection light source through the second focusing lens to enter the interference optical path system adjusted in step (1); the detection light source is divided into two strictly vertical light beams through the first plane beam splitter P1, one beam of light passes through P1→the laser plasma to be measured generated in step (3)→M1→P2 as the measurement light, and the other beam of light passes through P1→M2→P2 as the reference light. The measurement light and the reference light are combined into one beam of light after passing through the second plane beam splitter P2 and enter the receiving system. The white light entering the receiving system passes through the fourth focusing lens and the RGB filter aperture to form three coherent light beams carrying the phase information of the laser plasma. Subsequently, the three coherent light beams enter the color CCD, which is connected to a computer to display the interference fringe image in real time, so that multiple interference fringe images carrying the phase information of the laser plasma can be obtained.

[0029] While obtaining the interference fringe pattern through the laser interferometry method, the device effectively avoids the light source noise caused by the laser as the detection light source in the traditional interference device. At the same time, through the filtering of the RGB filter aperture in the receiving system, it effectively eliminates the influence of the surrounding environmental noise and improves the quality of the obtained interference fringe pattern. Moreover, compared with the traditional device, it can simultaneously obtain three interference fringe patterns carrying the laser plasma phase information, obtain more data graphs, and make the results more accurate, effective and comprehensive.

Claims

1. A laser plasma three-wavelength interference diagnostic device, characterized in that: It includes a detection light source system, a laser plasma excitation system, an interference light path system and a receiving system, wherein the detection light source system is used to generate a detection light source, the laser plasma excitation system is used to generate a laser plasma to be measured, the interference light path system is used to receive the detection light source, and the receiving system is used to generate three coherent light beams carrying laser plasma phase information; The interference optical path system includes a first plane beam splitter P1, a first plane reflector M1, a second plane beam splitter P2 and a second plane reflector M2. The detection light source is divided into two beams by the first plane beam splitter P1, one beam passes through the laser plasma to be measured, the first plane reflector M1 and the second plane beam splitter P2 as the measurement light; the other beam passes through the second plane reflector M2 and the second plane beam splitter P2 as the reference light. The reference light and the measurement light meet again after passing through the second plane beam splitter P2, and are combined into a beam of light to enter the receiving system; The receiving system comprises a fourth focusing lens (8), an RGB filter aperture (9), and a color CCD (10). The light from the interference optical path system passes through the fourth focusing lens (8) and the RGB filter aperture (9) to form three coherent light beams carrying laser plasma phase information. Subsequently, the three coherent light beams enter the color CCD (10). The color CCD is connected to a computer to display an interference fringe image in real time.

2. The laser plasma three-wavelength interference diagnostic device according to claim 1, characterized in that: The detection light source system comprises a first laser (1), a first focusing lens (2), a concave reflector (3) and a second focusing lens (4); the focal points of the first focusing lens (2), the concave reflector (3) and the second focusing lens (4) are located at the same position; laser light emitted by the first laser (1) is focused in the air through the first focusing lens (2), causing optical breakdown in the focal region, generating laser plasma, and the generated white flash as a detection light source passes through the second focusing lens (4) and enters the interference light path system.

3. The laser plasma three-wavelength interference diagnostic device according to claim 2, characterized in that: The laser plasma excitation system comprises a second laser (6) and a third focusing lens (7). The second laser (6) is focused in the air through the third focusing lens (7) to induce air breakdown, and the formed laser plasma serves as the laser plasma to be measured.

4. The laser plasma three-wavelength interference diagnostic device according to claim 3, characterized in that: A focal point of the third focusing lens (7) is located between the first plane beam splitter P1 and the first plane reflecting mirror M1 in the interference measurement system.

5. The laser plasma three-wavelength interference diagnostic device according to any one of claims 1 to 4, characterized in that: The fourth focusing lens (8), the RGB filter aperture (9) and the color CCD (10) are located on the same horizontal line.

6. The laser plasma three-wavelength interference diagnostic device according to any one of claims 3 to 4, characterized in that: The first laser (1) and the second laser (6) are Q-switched Nd:YAG lasers with an output wavelength of 1064 nm, a pulse width of 7 ns, and a maximum single pulse energy of 600 mJ.

7. The adjustment method of the laser plasma three-wavelength interference diagnostic device according to claim 3, characterized in that: The following steps are involved: (1) adjusting the interference optical path system, first placing a first plane beam splitter P1 to obtain two perpendicular split beams, placing a first plane reflector M1 to obtain two parallel split beams of equal height, placing a second plane reflector M2 to obtain the intersection position of beams with equal optical path lengths in space, and placing a second plane beam splitter P2 at the intersection of the beams with equal optical path lengths; (2) adjusting the detection light source system, the focal points of the first focusing lens (2), the concave reflector (3) and the second focusing lens (4) are located at the same point, the laser light generated by the first laser (1) is focused in the air through the first focusing lens (2), causing optical breakdown in the focal area, generating laser plasma, and the generated white flash as the detection light source passes through the second focusing lens (4) into the interference light path system adjusted in step (1); (3) adjusting the laser plasma excitation system, focusing the second laser (6) in the air through the third focusing lens (7), and generating laser plasma as the laser plasma to be measured, wherein a focus of the third focusing lens (7) is located in the optical path between the first plane beam splitter P1 and the first plane reflector M1 of the interference optical path system adjusted in step (1); (4) The receiving system is adjusted so that the fourth focusing lens (8), the RGB filter aperture (9) and the color CCD (10) are on the same horizontal line.

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