Multiband laser beam M2 factor detection system based on wavelength tuning metasurface

Abstract

The invention relates to the field of laser beam quality detection, in particular to a multiband laser beam M2 factor detection system based on a wavelength tuning metasurface, which comprises a control calculation module, a one-dimensional displacement table, the wavelength tuning metasurface and a detection module, and is characterized in that the calculation module is used for controlling the displacement of the one-dimensional displacement table and processing an image acquired by the detection module; the detection module is arranged on the one-dimensional displacement table and used for detecting the sizes of light spots on sampling points in the laser beam propagation direction; the wavelength tuning metasurface is used for realizing wavelength tuning of the incident light and converting the wavelength of the incident light which cannot be responded by the detection module into the wavelength of the incident light which can be responded by the detection module; by tuning the wavelength of the incident light, the response wavelength range of the detector is expanded, so that the near-infrared and intermediate-infrared detection of the visible light detector becomes possible, the wavelength response range of a common specific wave band light detector is expanded, the cost of an M2 detection system is reduced, and the quality detection of laser beams of corresponding wave bands is simpler and more efficient.

Description

Technical Field

[0001] The present invention relates to the field of beam quality detection technology, and in particular to a multi-band laser beam M2 factor detection system based on wavelength tuning metasurface. Background Art

[0002] The M2 factor of a laser beam, also known as the beam diffraction factor, is an important parameter for measuring the spatial quality of a laser beam. It is used to describe the focusing ability of a laser beam and the transmission efficiency of an optical system. Measuring the M2 factor is very important for evaluating the quality, reliability, and stability of a laser system, and is of great significance for the application of lasers in laser material processing, laser lighting, medical cosmetology, scientific research, and military applications.

[0003] At present, M2 meter and knife-edge method are usually used to measure the beam quality of laser. When the knife-edge method is used to measure M2, it is usually necessary to first select several sampling points along the laser transmission path, and use a power meter to detect the laser power. Then, the knife-edge is used to translate at each sampling point perpendicular to the laser transmission direction. During each translation, two points that make the laser power attenuate by a certain proportion are recorded successively. The difference between the two translation amounts is the spot size of the sampling point. After obtaining the spot diameter of each sampling point, the spatial distribution during the beam propagation process can be restored by fitting, thereby calculating the M2 value. From the principle of the knife-edge method, it can be seen that this method is a cumbersome, inefficient, and low-precision M2 factor measurement method. Compared with knife-edge measurement, the M2 instrument can image the light spot through a camera and directly read the spot size. In addition, its sampling process can be quickly completed by automatic mechanical scanning. Therefore, compared with the knife-edge method, the M2 instrument can obtain more sampling points and the scanning speed is faster. In addition, the camera's measurement of the spot size is more accurate than the knife-edge measurement. Therefore, compared with the knife-edge method, the M2 instrument can measure the M2 value of the laser beam more quickly and accurately. However, due to the high cost of infrared band detectors, the production cost of the M2 instrument in the infrared band is high and difficult to promote, especially in the mid-infrared band. The knife-edge method is currently mainly used to measure its M2. In addition, the applicable band of the existing M2 instrument is limited by the detector response band. The same system is usually unable to measure the M2 of multiple bands of laser beams, which restricts the wavelength application range of the same M2 instrument. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art that the M2 instrument has a single working band and the infrared band M2 instrument has a high manufacturing cost.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A multi-band laser beam M2 factor detection system based on wavelength tuning metasurface, characterized in that it includes a calculation module, a one-dimensional displacement stage, a wavelength tuning metasurface and a detection module; the calculation module is used to control the movement of the one-dimensional displacement stage; the detection module is arranged at the upper end of the one-dimensional displacement stage, and the wavelength tuning metasurface is arranged on the target surface of the detection module; the wavelength tuning metasurface is used to convert the wavelength of the incident light beam into a wavelength that the detection module can respond to; the detection module is used to detect the spot size of the incident light beam at several sampling points in the optical axis direction.

[0007] The one-dimensional translation stage can perform one-dimensional displacement under the control of the calculation module. The detection module is placed on the one-dimensional translation stage and can perform one-dimensional displacement under the drive of the one-dimensional translation stage, so as to measure the spot size at several sampling points on the propagation path of the measured light beam. The control calculation module can calculate the spot size data obtained by the detection module and output the M2 factor data. The wavelength tuning metasurface placed in front of the target surface of the detection module can convert the wavelength of the incident light beam into a wavelength that the detection module can respond to, thereby expanding the wavelength response range of the detection module. The system has a simple structure and is easy to operate, which solves the shortcomings of the prior art that the M2 instrument has a single working band and the infrared band M2 instrument has a high production cost.

[0008] Preferably, the wavelength tuning metasurface includes a plurality of sub-wavelength nanostructures, and the sub-wavelength nanostructures are arranged at equal intervals. The wavelength tuning metasurface is an array composed of a plurality of sub-wavelength nanostructures. When the incident light passes through the wavelength tuning metasurface, it will excite the second, third and other multiple harmonics in its sub-wavelength nanostructures, thereby realizing multiple frequency doublings such as double frequency and triple frequency of the incident light, and then realizing the wavelength conversion of the incident light beam. The wavelength conversion characteristics can be controlled by designing the sub-wavelength nanostructure. The multi-band laser beam M2 factor detection system based on the wavelength tuning metasurface can change its detectable band by replacing the wavelength tuning metasurface placed in front of the target of the detection module. At the same time, the wavelength tuning metasurface can be prepared according to specific needs, thereby realizing the expansion of the wavelength response range of the system.

[0009] Compared with the prior art, the advantages of the present invention are as follows: the present invention, the multi-band laser beam M2 factor detection system based on the wavelength tuning metasurface solves the shortcomings of the traditional M2 instrument in the mid-infrared and other bands, such as high cost and difficulty in promotion, and the single response band of the same system of the traditional M2 instrument and the lack of expansibility of the wavelength response range. The present invention introduces the wavelength tuning metasurface into the M2 factor measurement system, and with the help of the nonlinear characteristics of the wavelength tuning metasurface, realizes the tuning of the wavelength of the incident beam, thereby expanding the wavelength response range of the traditional detector, and further realizes a low-cost mid-wave infrared M2 detection system, and a multi-wavelength M2 detection system with an expansible wavelength response range. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of a multi-band laser beam M2 factor detection system based on a wavelength-tuned metasurface of the present invention;

[0011] Figure 2 It is a schematic diagram of the structure of the wavelength-tuned metasurface.

[0012] Reference numerals

[0013] 1-computing module; 2-one-dimensional translation stage; 3-wavelength tuning metasurface; 4-detection module; 5-subwavelength nanostructure. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0015] Implementation example Figure 1-2 The present embodiment shown is a multi-band laser beam M2 factor detection system based on a wavelength-tuned metasurface, comprising a calculation module 1, a one-dimensional translation stage 2, a wavelength-tuned metasurface 3 and a detection module 4; the calculation module 1 is used to control the movement of the one-dimensional translation stage 2; the detection module 4 is arranged at the upper end of the one-dimensional translation stage 2, and the wavelength-tuned metasurface 3 is arranged on the target surface of the detection module 4; the wavelength-tuned metasurface 3 is used to convert the wavelength of the incident light beam into a wavelength that the detection module 4 can respond to; the detection module 4 is used to detect the spot size of the incident light beam at several sampling points in the optical axis direction.

[0016] The wavelength tuning metasurface 3 includes a plurality of sub-wavelength nanostructures, and the sub-wavelength nanostructures are arranged at equal intervals.

[0017] like Figure 1 As shown, the first embodiment of the present invention proposes a multi-band laser beam M2 factor detection system based on a wavelength-tuned metasurface, comprising a computing module 1, a one-dimensional displacement stage 2, a wavelength-tuned metasurface 3, and a detection module 4; wherein the computing module 1 is used to control the displacement of the one-dimensional displacement stage 2 and process the image data collected by the detection module 4, and the detection module 4 is placed on the one-dimensional displacement stage 2, and can perform one-dimensional displacement under the drive of the one-dimensional displacement stage 2, so that the detection module 3 can perform multi-point sampling along the propagation direction of the light beam, and then obtain the spot size at several sampling points in the direction of the optical axis; the wavelength-tuned metasurface 3 is used to convert the incident light into a wavelength that the target surface of the detection module 4 can respond to.

[0018] Specifically, during the test, the optical axis of the measured light beam is aligned along the displacement direction of the one-dimensional translation stage 2 , and the light beam is incident on the target surface of the detection module 4 after passing through the wavelength tuning metasurface 3 .

[0019] It can be understood that the detection module 4 is driven by the one-dimensional displacement stage 2 to translate along the optical axis direction of the measured light beam and collect spot size data at several positions, and the M2 factor of the light beam can be obtained after calculation by the calculation module 1. The wavelength tuning metasurface 3 placed in front of the target surface of the detection module can convert the wavelength of the incident light beam into a wavelength that the detection module 4 can respond to, thereby expanding the response wavelength range of the detection module 4. Further, by replacing the wavelength tuning metasurface 3 with different wavelength conversion characteristics, the detection of the M2 factor of the multi-band light beam can be realized. Among them, the wavelength tuning metasurface 3 is composed of a number of sub-wavelength nanostructures, which can achieve local field enhancement, thereby enhancing the nonlinear effect of the metasurface, and then realizing that the incident light excites multiple harmonics such as the second harmonic and the third harmonic on the metasurface, thereby converting the wavelength of the incident light into a wavelength that the detection module 4 can respond to.

[0020] In an embodiment, the wavelength-tuning metasurface can be attached to the target surface of the camera in the form of a patch, thereby realizing the conversion of the detection module to a specific wavelength.

[0021] In the embodiment, the wavelength-tuning metasurface 3 can be placed in front of the target surface of the detection module 4 by mechanical plugging and unplugging, and the wavelength-tuning metasurface 3 with specific conversion characteristics can be flexibly selected and placed in front of the target surface of the detection module 4 according to needs.

[0022] In the embodiment, the wavelength-tuned metasurface 3 is composed of a plurality of sub-wavelength nanostructures 5, wherein the sub-wavelength nanostructures 5 can be of any shape and size, such as regular shapes such as rectangles, trapezoids, triangles, polygons, etc., or irregular shapes, such as protruding columns or recessed holes.

[0023] In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0024] Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-band laser beam M2 factor detection system based on wavelength-tunable metasurface, characterized in that: It comprises a computing module, a one-dimensional displacement stage, a wavelength tuning metasurface and a detection module; the computing module is used to control the movement of the one-dimensional displacement stage; the detection module is arranged at the upper end of the one-dimensional displacement stage, and the wavelength tuning metasurface is arranged on the target surface of the detection module; the wavelength tuning metasurface is used to convert the wavelength of the incident light beam into a wavelength that the detection module can respond to; the detection module is used to detect the spot size of the incident light beam at several sampling points in the optical axis direction.

2. According to claim 1, a multi-band laser beam M2 factor detection system based on wavelength-tunable metasurface is characterized in that: The wavelength tuning metasurface includes a plurality of sub-wavelength nanostructures, and the sub-wavelength nanostructures are arranged at equal intervals.

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