A device for outputting a high-power homogenized square light spot

Abstract

The application provides a device for outputting high-power homogenized square light spot, comprising: a laser source for emitting laser; a core comprising a first square core and a second square core, the first square core and the second square core being aligned and fused in a rotating mode of 40-45 degrees; a cladding which is circular and covers the core; a coupling device for coupling the laser emitted by the laser source into the first square core; and an output device for collimating the light output by the second square core and blocking the light leakage of the cladding. The application has the beneficial effects that: after the laser passes through the fusion point of the first square core and the second square core, part of the laser is introduced into the cladding, more high-order modes of the second square core are excited, and the output light spot is more uniform; the first square core can be coupled in with small NA to avoid end face damage, greatly reduce the risk of fiber damage at the input end, greatly reduce the light leakage, improve the transmission efficiency, and greatly reduce the requirement for the laser mode.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more particularly to a device for outputting a high-power, uniform square light spot. Background Technology

[0002] High-power homogenized square laser spots have wide applications in solar cell processing, especially in laser doping. As the most important clean energy source of the future, improving the conversion efficiency of solar cells has always been the goal of all energy workers. Laser doping is an important part of solar cell processing, and the homogenization effect of the laser spot directly affects the uniformity of doping, thus affecting the improvement of cell conversion efficiency.

[0003] Currently, the laser source commonly used for laser doping is nanosecond green light, which is converted from a Gaussian spot to a uniform square spot using a diffractive optical element (DOE). This method places very stringent requirements on the laser mode and spot stability, demanding that the spot be extremely Gaussian and have excellent sphericity to achieve a uniform square spot. Furthermore, even slight drift in the optical path can affect the uniformity and shape of the square spot, leading to frequent equipment downtime for adjustments and impacting the battery processing efficiency.

[0004] For example, in Chinese patent CN107678086A, directly coupling a single-mode Gaussian spot into a square optical fiber using NA (numerical aperture) matching cannot achieve a good homogenization effect. A large NA injection (far exceeding the fiber NA) is required to homogenize the square spot, but this will lead to problems such as fiber end-face damage and low transmission efficiency.

[0005] In Chinese patent CN109683252 A, a single-mode Gaussian spot is first coupled with a small NA (nanocoupler) into a section of square fiber to achieve a multimode square spot output with poor homogenization. Then, the NA is matched and coupled into another section of square fiber to achieve a homogenized square spot output. This method requires two sets of fiber coupling devices, which places high demands on mechanical stability and is not conducive to engineering implementation.

[0006] Chinese patent CN 108474906 A describes a method for achieving homogenized square beam output by fusion splicing a mode-mixing homogenizing fiber with a square fiber. The mode-mixing homogenizing fiber is used to convert a single-mode Gaussian beam into a homogenized beam. This method uses asymmetric doping regions in the fiber core to excite as many higher-order modes as possible, forming a flat-top beam through mode mixing for laser shaping. However, the geometrically asymmetric design of the doping regions makes precise control over their size and refractive index difficult, hindering standardized fiber fabrication and resulting in poor batch consistency and a high defect rate in the produced laser-shaped fibers. Summary of the Invention

[0007] In view of this, in order to solve the problem of homogenization of square light spots, embodiments of the present invention provide a device for outputting high-power homogenized square light spots.

[0008] Embodiments of the present invention provide a device for outputting a high-power homogenized square light spot, comprising:

[0009] A laser source, used to emit laser light;

[0010] The fiber core includes a first square fiber core and a second square fiber core, wherein the end faces of the first square fiber core and the second square fiber core are aligned and fused together by rotating 40 to 45 degrees.

[0011] The cladding is circular and covers the outside of the fiber core;

[0012] A coupling device for coupling the laser emitted by the laser source into the first square fiber core;

[0013] And an output device for collimating the light output from the second square fiber core and blocking light leakage from the cladding.

[0014] Furthermore, the cross-sectional shape and size of the first square fiber core and the second square fiber core are the same.

[0015] Furthermore, the second square fiber core is rotated 45° relative to the first square fiber core.

[0016] Furthermore, the first square fiber core and the second square fiber core have the same optical fiber numerical aperture.

[0017] Furthermore, the output device includes a first output device for collimation and a second output device for filtering out cladding light.

[0018] Furthermore, the first output device is an aspherical mirror; and / or, the second output device is a light-absorbing block with a hole.

[0019] Furthermore, the cladding is a double cladding, comprising an inner cladding and an outer cladding, both of which are circular. The inner cladding wraps around the fiber core, and the outer cladding wraps around the inner cladding.

[0020] Furthermore, it also includes a first fiber end cap, which is connected to the input end of the first square fiber core; and / or, it also includes a second fiber end cap, which is connected to the output end of the second square fiber core.

[0021] Furthermore, the coupling device is a spherical lens.

[0022] Furthermore, the laser source is a nanosecond laser.

[0023] The beneficial effects of the technical solutions provided by the embodiments of the present invention are as follows:

[0024] 1. The present invention provides a device for outputting a high-power homogenized square light spot, wherein a first square fiber core and a second square fiber core rotate relative to each other. After the laser passes through the fusion point of the first and second square fiber cores, part of it is introduced into the cladding, thereby exciting more high-order modes of the second square fiber core and making the output light spot more uniform.

[0025] 2. The device for outputting a high-power uniform square light spot according to the present invention has a first square fiber core that can couple the input with a small NA to avoid end face damage, greatly reducing the risk of fiber damage at the input end, significantly reducing light leakage, and improving transmission efficiency; and coupling the laser into the square fiber, compared with the DOE solution, the requirements for the laser mode are greatly reduced. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a device for outputting a high-power homogenized square light spot according to the present invention;

[0027] Figure 2 This is a schematic diagram of the cross-section of the fiber core and cladding;

[0028] Figure 3 The image shows the homogenized spot pattern obtained using a single-fiber large NA coupling scheme.

[0029] Figure 4 This is a homogenized light spot image obtained using the device of the present invention that outputs a high-power homogenized square light spot.

[0030] In the figure: 1-Coupled device, 21-First fiber end cap, 31 / 32-Double clad fiber, 4-Fusion splice, 22-Second fiber end cap, 5-First output device, 6-Second output device, 311-First square fiber core, 321-Second square fiber core, 322-Inner cladding, 323-Outer cladding. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0032] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0033] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can 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.

[0036] Please refer to Figure 1 The present invention provides a device for outputting a high-power homogenized square light spot, which mainly includes a laser source, a fiber core, a cladding, a coupling device 1, and an output device.

[0037] The laser source is used to emit laser light. In this embodiment, the laser source is a nanosecond laser with a center wavelength of 532 nm.

[0038] like Figure 2 As shown, the fiber core includes a first square fiber core 311 and a second square fiber core 321. The end faces of the first square fiber core 311 and the second square fiber core 321 are aligned and fused together by rotating them by 40 to 45 degrees. In this embodiment, the second square fiber core 321 is rotated 45° relative to the first square fiber core 311, and the fusion connection increases stability.

[0039] Continue as Figure 2 As shown, the first square fiber core 311 and the second square fiber core 321 have the same cross-sectional shape and size. Specifically, the first square fiber core 311 and the second square fiber core 321 have the same side length and the same optical fiber numerical aperture (NA). In this embodiment, the first square fiber core 311 and the second square fiber core 321 have a NA of 50 μm and an NA of 0.1. The square fiber core has a symmetrical structure, which makes it easier to control product consistency and yield.

[0040] The cladding is circular and covers the fiber core. Specifically, the cladding is a double cladding, comprising an inner cladding 322 and an outer cladding 323, both circular. The inner cladding 322 encloses the fiber core, and the outer cladding 323 encloses the inner cladding 322. Here, the fiber core and its outer cladding can be formed by fusion splicing two segments of double-clad optical fibers 31 and 32. The fiber core inside one segment of double-clad optical fiber 31 is the first square fiber core 311, and the fiber core inside the other segment of double-clad optical fiber 32 is the second square fiber core 321. The fiber cores inside the two segments of double-clad optical fibers 31 and 32 are fused at splice point 4.

[0041] The coupling device 1 is used to couple the laser emitted by the laser source into the first square fiber core 311. As in this embodiment, the coupling device 4 is a spherical lens with a focal length of 30mm.

[0042] The output device is used to collimate the light output from the second square fiber core 321 and block light leakage from the cladding. The output device includes a first output device 5 for collimation and a second output device 6 for filtering out cladding light. In this embodiment, the first output device 5 is an aspherical lens with a focal length of 20mm, which collimates the light output from the second square fiber core 321; the second output device 6 is a light-absorbing block with holes, which absorbs light leakage from the cladding.

[0043] Furthermore, the device for outputting a high-power homogenized square beam also includes a first fiber end cap 21 and a second fiber end cap 22. The first fiber end cap 21 is fused to the input end of the first square fiber core 311, protecting the input end face of the first square fiber core 311 and improving transmittance. The second fiber end cap 22 is fused to the output end of the second square fiber core 321, protecting the output end of the second square fiber core 321 and improving transmittance.

[0044] When the device for outputting a high-power homogenized square light spot is in operation, the light source outputs a 60W Gaussian beam with an output spot size of approximately 2mm. The coupling device 1 couples the Gaussian beam into the first square fiber core 311, whose numerical aperture (NA) is approximately 0.03. After passing through the fusion point of the first square fiber core 311 and the second square fiber core 321, part of the light enters the cladding from the extension directions of the four corners of the first square fiber core 311, further exciting the higher-order modes of the second square fiber core 321, making the output light spot more uniform. The homogenized beam is then input into the output device for collimation and cladding light filtering to obtain a homogenized square light spot.

[0045] Because this application couples the laser into a square optical fiber, the requirements for the laser mode are significantly reduced compared to the DOE beam homogenization scheme in the prior art. The DOE scheme requires a laser beam quality M² < 1.1 and a circularity greater than 95%. This application does not have high requirements for the laser mode; M² < 1.3 and a circularity greater than 80% are sufficient. This reduces the requirements for the laser, and most commercially available lasers can meet these requirements.

[0046] Compared to the previous approach of achieving homogenization through single-fiber large-NA coupling, this application significantly reduces the numerical aperture (NA) of the input fiber. The previous approach, which required a large NA injection to achieve a homogenized square spot, necessitated an NA greater than 0.15. Figure 3 The homogenized light spot shown is achieved using the high-power output homogenization square light spot device of this application, which can achieve this with an input of 0.03NA. Figure 4 The homogenized light spot shown is Figure 3 , Figure 4 The white line in the middle represents the CCD camera sampling line. A comparison shows that... Figure 3 , Figure 4 The light spot uniformity effect is similar. However, in this application, the light spot area input to the first square fiber core 311 by the coupling device 1 is increased by about 25 times, which greatly reduces the risk of fiber damage at the input end, significantly reduces light leakage, and improves transmission efficiency.

[0047] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0048] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for outputting a high-power, homogenized square light spot, characterized in that, include: A laser source, used to emit laser light; The fiber core includes a first square fiber core and a second square fiber core. The end faces of the first square fiber core and the second square fiber core are aligned and fused together by rotating 40 to 45 degrees. The cross-sectional shape and size of the first square fiber core and the second square fiber core are the same. The optical fiber numerical aperture of the first square fiber core and the second square fiber core are the same. The cladding is circular and covers the outside of the fiber core; A coupling device for coupling the laser emitted by the laser source into the first square fiber core; And an output device for collimating the light output from the second square fiber core and blocking light leakage from the cladding.

2. The device for outputting a high-power homogenized square light spot as described in claim 1, characterized in that: The second square fiber core is rotated 45° relative to the first square fiber core.

3. The device for outputting a high-power homogenized square light spot as described in claim 1, characterized in that: The output device includes a first output device for collimation and a second output device for filtering out cladding light.

4. The device for outputting a high-power homogenized square light spot as described in claim 3, characterized in that: The first output device is an aspherical mirror; and / or, the second output device is a light-absorbing block with a hole.

5. The device for outputting a high-power homogenized square light spot as described in claim 1, characterized in that: The cladding is a double cladding, consisting of an inner cladding and an outer cladding, both of which are circular. The inner cladding wraps around the fiber core, and the outer cladding wraps around the inner cladding.

6. The device for outputting a high-power homogenized square light spot as described in claim 1, characterized in that: It also includes a first fiber end cap, which is connected to the input end of the first square fiber core; and / or, it also includes a second fiber end cap, which is connected to the output end of the second square fiber core.

7. The device for outputting a high-power homogenized square light spot as described in claim 1, characterized in that: The coupling device is a spherical lens.

8. The device for outputting a high-power homogenized square light spot as described in claim 1, characterized in that: The laser source is a nanosecond laser.

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