A method and apparatus for measuring the shielding effect of a pulsed laser excited plasma

Abstract

The application provides a kind of measurement method and equipment of pulsed laser excited plasma shielding effect. Specifically includes: preparing sample with small hole in advance;Through the spatial composition of pulsed laser and the laser to be tested by dichroic mirror, and act on the small hole position of sample;Close the pulsed laser, open the laser to be tested, measure the power of the beam after passing through the small hole and its curve changing with time, as reference;Synchronous opening of pulsed laser and the laser to be tested, pulsed laser will excite plasma on the surface of small hole, the transient change (nanosecond time scale) plasma will shield the transmitted laser to be tested, by measuring the energy of the laser transmitted after shielding, and comparing with the result when not shielded previously, the shielding effect of pulsed laser excited plasma can be determined. The research results obtained by this method can further guide the selection of composite laser action parameters, so as to further optimize the efficiency and quality of composite laser processing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser processing, in particular to a method and equipment for measuring shielding effect of plasma excited by pulsed laser. BACKGROUND

[0002] In the field of laser processing research and application, it is always difficult to improve the efficiency and quality of laser and material interaction. At this point, common short pulse laser, ultrafast pulse laser often have high processing quality, but due to the limitation of output energy, the processing efficiency is low; on the other hand, long pulse laser, continuous laser has high processing efficiency, but the processing quality is poor. Therefore, in the field of improving laser processing quality and efficiency, new processing methods are often needed.

[0003] Composite laser, by combining lasers with different pulse widths and pulse energies, can form a combination of multiple types of lasers in time and space, such as combining ultrafast laser and continuous laser, so as to fully combine the processing efficiency and quality advantages of continuous laser and pulsed laser, and improve the laser processing effect.

[0004] However, during the interaction of composite laser and material, high peak power density pulsed laser will excite plasma on the material surface, and the excited plasma will have a significant shielding effect on the other laser in the composite, i.e. reducing the transmission energy of the other beam, affecting the processing efficiency and quality. Among them, the typical problem is that to improve the action efficiency of composite laser, the inherent idea is to improve the energy of pulsed laser, but due to the existence of plasma shielding, further increasing the energy of pulsed laser will reduce the power of transmitted continuous laser, which will reduce the action efficiency and quality. At the same time, the plasma shielding makes it difficult to determine the interaction mechanism of composite laser and material and to control the action efficiency, which becomes a new problem. Therefore, new methods and equipment are needed to accurately and quantitatively determine the shielding effect of plasma excited by pulsed laser, so as to further guide the selection of composite laser action parameters and further optimize the processing efficiency and quality of composite laser. SUMMARY

[0005] To solve the above problems, the present application provides a method and equipment for measuring shielding effect of plasma excited by pulsed laser, comprising the following steps:

[0006] (1) Prepare a sample containing holes with different diameters in advance.

[0007] (2) Realize spatial combination of pulsed laser and laser to be tested by dichroic mirror, and act on the small hole position of the sample.

[0008] (3) Turn off the pulsed laser, turn on the laser to be tested, measure the power of the laser passing through the small hole and its curve changing with time as a reference.

[0009] (4) Turn on the pulsed laser and the laser to be tested at the same time, the pulsed laser will excite plasma on the surface of the small hole, the transient change (nanosecond time scale) plasma will shield the transmitted laser to be tested, by measuring the energy of the laser passing through after shielding and comparing with the previous results, the shielding effect of the plasma excited by the pulsed laser can be determined.

[0010] Further, the diameter of the through hole is 10 μm-10 mm.

[0011] Further, the pulsed laser is a nanosecond laser, a picosecond laser or a femtosecond laser.

[0012] Further, the laser to be tested is a continuous laser, a millisecond laser, a nanosecond laser, a picosecond laser, a femtosecond laser, etc.

[0013] Further, the pulsed laser and the laser to be tested are focused on the surface of the sample.

[0014] Further, the transmittance of the dichroic mirror for the pulsed laser is not less than 90%, and the reflectivity for the laser to be tested is not less than 95%.

[0015] Further, the spot diameter of the pulsed laser and the laser to be tested focused on the sample is greater than the diameter of the sample through hole.

[0016] Further, the energy of the pulsed laser is absorbed by the optical filter, so that the energy detected is the energy of the laser to be tested.

[0017] Advantages

[0018] The present application mainly has the following advantages:

[0019] 1. The pulsed laser and the laser to be tested are coupled through the dichroic mirror, the arrangement of the optical path remains unchanged during the entire experiment, and only the switch of the pulsed laser is controlled to determine the shielding effect of the pulsed laser on the laser to be tested, the experimental steps are simple, and the laser parameters can be easily adjusted for multiple experiments.

[0020] 2. Compared with the actual processing process, only the sample is replaced by a sample with a small through hole, without changing any other variables, the experimental process is basically consistent with the effect of the composite laser on the sample in the actual processing process, and the residual pulsed laser can be eliminated by the optical filter to avoid interference, and the experimental results are accurate.

[0021] 3, the shielding effect of the plasma excited by the pulsed laser on the laser to be tested can be studied, accurate and quantitative analysis can be carried out, the influence of the plasma shielding effect on the interaction of the composite laser and the material can be determined, so that the parameter selection in the composite laser processing process is guided, and the efficiency and quality of the composite laser processing are optimized. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The technical scheme of the plasma shielding effect measurement method of the application is shown in the figure.

[0023]

Explanation of reference numerals

[0024] 1, pulsed laser; 2, collimated transmitted pulsed laser; 3, dichroic mirror (transmits pulsed laser and reflects laser to be tested); 4, laser to be tested; 5, collimated transmitted laser to be tested; 6, plasma excited by pulsed laser; 7, target material containing micropores; 8, small-diameter through hole; 9, attenuated laser to be tested; 10, optical filter (passes the wavelength of the laser to be tested and absorbs the wavelength of the pulsed laser); 11, power detector and oscilloscope. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical schemes and advantages of the application clearer, specific embodiments will be described in detail below with reference to the drawings. It should be noted that the description of these embodiments is used to help understand the application, but does not constitute a limitation on the application.

[0026] Example 1

[0027] It is known that the ablation effect on an alumina ceramic sample can be improved by the combined action of a femtosecond laser and a continuous wave laser. In order to guide the parameter selection of the composite laser action, it is necessary to further measure the shielding effect of the plasma after the femtosecond laser acts on the sample on the continuous wave laser.

[0028] In this embodiment, the pulsed laser is a femtosecond laser with parameters of 4 mJ, 1 kHz and 800 nm, the laser to be tested is a continuous wave laser with parameters of 500 W and 1080 nm, and the sample is an alumina ceramic sheet with a size of 30 mm x 30 mm x 3 mm and a small hole with a diameter of 0.1 mm in the center of the sample.

[0029] As shown in the figure, the femtosecond laser 2 and the continuous wave laser 5 are coupled to form a composite laser after passing through a dichroic mirror with an incident angle of 45°, and act on the alumina ceramic sheet 7, and attenuate after passing through the small hole 8. The attenuated laser 9 passes through the optical filter 10, which only passes the wavelength of the continuous wave laser and absorbs the wavelength of the femtosecond laser, and the remaining continuous wave laser reaches the power detector and oscilloscope 11, and the laser power can be detected.

[0030] In the experimental procedure, first, the femtosecond laser 1 is turned off, and the continuous laser 4 is turned on, so that the continuous laser is not shielded by the plasma, and the laser power at this time is detected by the power detector and oscilloscope 11 as a reference; then, the femtosecond laser 1 and the continuous laser 4 are turned on synchronously, the plasma 6 generated after the femtosecond laser acts on the aluminum oxide ceramic sheet 7 will have a shielding effect on the continuous laser, and the attenuated laser is detected by the power detector and oscilloscope 11. By comparing the power values detected before and after, the shielding effect of the plasma excited by the femtosecond laser on the continuous laser can be determined.

[0031] Example 2

[0032] Nanosecond / millisecond composite laser drilling can achieve high efficiency and excellent quality. In order to further optimize the parameters, the shielding effect of the plasma excited by the nanosecond laser on the millisecond laser is studied.

[0033] In this embodiment, the pulsed laser is a nanosecond laser with parameters of 4mJ, 3kHz, 780nm, and 17ns, the laser to be tested is a millisecond laser with parameters of 700W, 50Hz, duty cycle of 10%, and wavelength of 1070nm, and the sample is a 96% aluminum oxide ceramic sheet with a size of 30mm x 30mm x 1mm, and a small hole with a diameter of 0.2mm in the center of the sample.

[0034] As shown in the drawing, the nanosecond laser 2 and the millisecond laser 5 are coupled to form a composite laser through a dichroic mirror with an incident angle of 45°, and act on the aluminum oxide ceramic sheet 7, and attenuate after passing through the small hole 8. The attenuated laser 9 passes through the optical filter 10, which only transmits the wavelength of the millisecond laser and absorbs the wavelength of the nanosecond laser, and the remaining millisecond laser reaches the power detector and oscilloscope 11 to detect the laser power.

[0035] In the experimental procedure, first, the nanosecond laser 1 is turned off, and the millisecond laser 4 is turned on, so that the millisecond laser is not shielded by the plasma, and the laser power at this time is detected by the power detector and oscilloscope 11 as a reference; then, the nanosecond laser 1 and the millisecond laser 4 are turned on synchronously, the plasma 6 generated after the nanosecond laser acts on the aluminum oxide ceramic sheet 7 will have a shielding effect on the millisecond laser, and the attenuated laser is detected by the power detector and oscilloscope 11. By comparing the power values detected before and after, the shielding effect of the plasma excited by the nanosecond laser on the millisecond laser can be determined.

[0036] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of measuring a shielding effect of a pulsed laser excited plasma, characterized by, The application relates to a method for testing the shielding effect of plasma generated by a pulsed laser on a test laser. The method comprises the following steps: Step 1, preparing a sample in advance, which comprises through holes with different diameters; Step 2, realizing spatial compounding of a pulsed laser and a test laser through a dichroic mirror, and acting on a small hole position of the sample; Step 3, closing the pulsed laser, opening the test laser, and measuring the power of the test laser after passing through the small hole and the curve of the power change with time through a power detector and an oscilloscope, as a reference; 2. The method of claim 1, wherein the method is characterized by: Step 4, synchronously opening the pulsed laser and the test laser, the pulsed laser will excite plasma on the surface of the small hole, the plasma will shield the transmitted test laser, the attenuated test laser is detected through a power detector and an oscilloscope, including: the pulsed laser and the test laser are coupled to form compound laser after passing through the dichroic mirror with an incident angle of 45 degrees, act on the sample, attenuate after passing through the small hole, the attenuated laser passes through a filter, the filter only passes the wavelength of the test laser and absorbs the wavelength of the pulsed laser, the remaining test laser reaches the power detector and the oscilloscope, and the laser power can be detected, the shielding effect of the plasma excited by the pulsed laser on the test laser is determined by measuring the power of the laser after shielding and comparing with the previous result.

3. The method of claim 1, wherein the method is characterized by: The diameter of the through hole is 10 microns to 10 millimeters.

4. The method of claim 1, wherein the method is a method of measuring a shielding effect of a pulsed laser-induced plasma, characterized by, The pulsed laser is a nanosecond laser, a picosecond laser or a femtosecond laser.

5. The method of claim 1, wherein the method is a method of measuring a shielding effect of a pulsed laser-induced plasma, the method comprising: The test laser is a continuous laser, a millisecond laser, a nanosecond laser, a picosecond laser or a femtosecond laser.

6. The method of claim 1, wherein the method is a method of measuring a shielding effect of a pulsed laser-induced plasma, the method comprising: The pulsed laser and the test laser are focused on the surface of the sample.

7. The method of claim 1, wherein the method is a method of measuring a shielding effect of a pulsed laser-induced plasma, the method comprising: The transmittance of the dichroic mirror for the pulsed laser is not less than 90%, and the reflectivity for the test laser is not less than 95%.

8. The method of claim 1, wherein the method is a method of measuring a shielding effect of a pulsed laser-induced plasma, the method comprising: The spot diameters of the pulsed laser and the test laser on the sample are larger than the diameter of the through hole of the sample. The filter is used to absorb the energy of the pulsed laser, so that the detected energy is the energy of the test laser.

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