CN103941406B - High-power semiconductor laser optical shaping method and device based on beam expanding - Google Patents

Abstract

The invention provides a semiconductor laser optical shaping method and device. High-power uniform light spots can be obtained, and cost is low. The principle includes that firstly, beams emitted by semiconductor laser stacks are collimated and then exponentially expanded, laser beams with energy in Gaussian distribution are transformed into flat-top beams with uniform energy density distribution, and secondly, expanded laser is focused by a focusing system, so that uniformity of the light spots can be achieved and improved.

Description

A method and device for optical shaping of high-power semiconductor lasers based on beam expansion

technical field

The invention belongs to the field of laser applications, and in particular relates to a laser beam expander.

Background technique

Laser has the advantages of good monochromaticity, good directionality, good coherence and high brightness, and has been widely used in various fields of national economy. The diameter of the beam emitted by the laser is very small, usually 1-2mm. In some specific applications, such as laser processing, laser detection and laser lighting, it is necessary to use a uniform laser beam with a larger diameter. The laser is optically shaped to achieve this.

Currently commonly used optical shaping methods can use the following methods:

1. Reflective optical shaping method: Usually, optical waveguide can be used for optical shaping, but there is a serious depth of focus problem with this method, resulting in short working distance and unchangeable working distance;

2. Transmissive optical shaping method: after collimating the laser light source, it is directly focused. The final output laser of this method is a flat-top spot with an interval of bright and dark phases, and the energy is not uniform; in addition, a combination of negative lens and positive lens can also be used This method of optical shaping is expensive because of the use of many lenses; in addition, the light source can be cut and rearranged before focusing, but the optical devices used in the process of cutting and rearranging are more complicated and costly. At the same time, the compression ratio between the light-emitting surface and the final required spot size is small, resulting in uneven output spots.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a semiconductor laser optical shaping method and its device, which can obtain high-power uniform light spots with low cost.

The principle of the present invention is: firstly collimate the light emitted by the stack of semiconductor lasers and then expand the beam exponentially, convert the laser beam with energy Gaussian distribution into a flat top beam with uniform energy density distribution, and then expand the beam through the focusing system The final laser is focused to improve the uniformity of the spot, which can achieve the uniformity of the spot.

The implementation plan is as follows:

The high-power semiconductor laser optical shaping method includes:

Collimating the light emitted by the semiconductor laser stack;

Doubly expand the collimated laser beam;

Converge the doubled beam expanded laser to get the spot of required size;

Among them, the beam expansion link adopts a combination of a beam splitter and a reflector, and the transmitted light of the beam splitter and the reflected light of the reflector exit in parallel to realize beam expansion.

The aforementioned beam expansion link can be provided with a combination of multi-stage beam splitters and reflectors to perform multi-stage beam expansion.

Based on the above-mentioned high-power semiconductor laser optical shaping method, the present invention also proposes several specific high-power semiconductor laser optical adjustment devices:

The first high-power semiconductor laser optical device based on beam expansion, including semiconductor laser stacks, collimating lens groups, beam splitting systems and focusing systems arranged in sequence along the optical path, the semiconductor laser stack consists of several semiconductor laser units Composition; the light splitting system includes n component optical modules arranged in sequence along the laser light emitting direction, each component optical module includes a beam splitter and a reflector, and the beam splitting surface of the beam splitter and the reflecting surface of the reflector are arranged parallel to each other along the height direction and parallel to the laser beam The light output direction is at an angle of 30-60°; after the laser beam passes through the beam splitter, half of the energy of the light is transmitted directly, and the other half of the energy of the light is reflected to the reflector and then reflected again, and exits parallel to the light directly transmitted by the beam splitter;

The beam splitter of the first component optical module is equivalent to the stacking height of the semiconductor laser stack; the size of each component optical module is multiplied sequentially, and the light beam emitted by the mth component optical module is incident on the beam splitter of the m+1th component optical module, 1 ≤m<n, m is the sequence number of the light splitting module, and the sequence number is arranged according to the order in which the laser passes through; the focusing system is used to focus and shape the beam expanding laser to obtain a spot of required size.

The focusing system described above employs a focusing lens group.

The optical splitting module can be implemented in the following two types.

the first sort:

In the light splitting module, the reflector can be a total reflection plane mirror or a total reflection prism. The material of the total reflection plane mirror can be glass or metal, and the surface is coated with a high-reflection film, and the material of the high-reflection film is metallic silver or aluminum; or the high-reflection film adopts a multilayer dielectric reflection film.

In the beam splitting module, the reflector can also use a polarizing device; if the polarization characteristic of the semiconductor laser stack is TE light, the polarizing device will fully reflect the TE light; or if the polarization characteristic of the semiconductor laser stack is TM light, then the polarizing device will reflect TM light total reflection. The polarizing device may specifically be a polarizer, a polarizer or a polarization beam combiner.

In the beam splitting module, the beam splitter can be a beam splitter, the base material of the beam splitter is glass, the surface of the beam splitter is coated with a semi-transparent and semi-reflective film, and the material of the semi-transparent and semi-reflective film is a zinc sulfide-magnesium fluoride film system.

The second category:

The light splitting module can also use a prism combination to realize the functions of a beam splitter and a reflector as a whole. The prisms in the prism combination are closely fitted to each other, so that there is a side facing the stack of semiconductor lasers and perpendicular to the laser light output direction as a light splitting module. The light incident surface has another side parallel to the light incident surface as the light exit surface of the light splitting module (according to the above basic scheme, the light incident surface and the light exit surface of the first component optical module are all equivalent to the stack height of the semiconductor laser stack , the size of the light incident surface and the light exit surface of each component optical module is doubled in turn); there is a bonding surface inside the prism combination coated with a semi-transparent and semi-reflective film as the light splitting surface of the beam splitter, which is parallel to the light splitting surface and the light incident surface A side adjacent to the surface is used as a reflective surface of the reflector.

This type of light-splitting module is preferably a combination of a parallelepiped prism and a triangular prism. The parallelepiped prism has a unique side facing the stack of semiconductor lasers and is perpendicular to the laser light-emitting direction as the light incident surface of the light-splitting module. The included angle with the side is The adjacent side of the acute angle closely fits the triangular prism, and the mating surface is coated with a semi-transparent and semi-reflective film as the splitting surface of the beam splitter, and the adjacent side with an obtuse angle with the side is used as the reflective surface of the reflector; the triangular prism It also has an outer surface perpendicular to the light emitting direction of the laser, serving as the light emitting surface of the light splitting module.

Preferably, the beam-splitting surface of the beam splitter and the reflection surface of the reflector are both set at an angle of 45° to the laser light-emitting direction. For the combination of the above-mentioned parallelepiped prism and triangular prism, it is equivalent to using parallelepiped prisms with inner angles of 45° and 135° to ensure that both the splitting surface and the reflecting surface are at an angle of 45° to the laser light emitting direction.

The second high-power semiconductor laser optical device based on beam expansion includes a semiconductor laser stack, a collimating lens group, a beam splitting system, and a focusing system arranged in sequence along the optical path. N beamsplitters and a total reflection mirror are arranged in sequence, the first beamsplitter is at the same height as the stack of semiconductor lasers, and the n beamsplitters and total reflection mirrors are arranged in parallel and equally spaced to output light from the stack of semiconductor lasers The direction is set at 30-60°; the transmitted light of the first beam splitter and the reflected light of the remaining n-1 beam splitters and the total reflection mirror together form a laser beam expansion; the focusing system is used to perform beam expansion on the expanded laser beam Focus shaping to obtain the desired size of the spot;

The light transmittance of the n beamsplitters is different, and the transmitted light energy of the first beamsplitter is equal to the reflected light energy of the remaining n-1 beamsplitters and the total reflection mirror:

The transmittance of the first beam splitter is 1/(n+1), and the reflectance is n/(n+1);

The transmittance of the mth beam splitter is (n-m+1)/(n-m+2), and the reflectance is 1/(n-m+2);

Among them, n is the total number of beam splitters, m is the sequence number of the beam splitter, 1<m≤n, and the sequence numbers are arranged according to the order in which the laser light passes through.

The third high-power semiconductor laser optical device based on beam expansion includes semiconductor laser arrays, collimating lens groups, beam splitting systems, and focusing systems arranged sequentially along the optical path, and the semiconductor laser array is stacked by several semiconductor laser units Composition, the beam splitting system includes n beam splitters arranged in sequence along the light emitting direction of the semiconductor laser stack and a total reflection mirror arranged at the end, wherein the first beam splitter is equivalent to the stack height of the semiconductor laser stack, and the n beam splitters and The total reflection mirrors are arranged in parallel and at equal intervals, and are set at 30-60° to the light output direction of the stack of semiconductor lasers; the reflected light of n beam splitters and total reflection mirrors together form laser beam expansion; the focusing system is used to expand the beam The laser is focused and shaped to obtain the desired size of the spot;

The light transmittance of the n beamsplitters is different, so that the reflected light energy of the n beamsplitters and the total reflection mirror is equal:

The reflectance of the mth beam splitter is 1/(n-m+2), and the transmittance is (n-m+1)/(n-m+2);

Among them, n is the total number of beam splitters, m is the array number of beam splitters, 1≤m≤n, and the array numbers are arranged according to the order in which the laser light passes through.

The above-mentioned collimating lens group can use a combination of a fast-axis collimating lens and a slow-axis collimating lens or one of the two, wherein the fast-axis collimating lens is a collimating D-type aspheric lens, and the slow-axis collimating lens is a single array Cylindrical lens.

The present invention has the following advantages:

(1) Increase the size of the light-emitting surface, increase the compression ratio between the light-emitting surface and the final spot size, and finally improve the uniformity. It can be used in laser welding and laser lighting where there is a high requirement for laser uniformity.

(2) The implementation cost is low and the components are small.

(3) The structure is compact and suitable for practical use.

(4) According to the optical shaping method and device of the high-power semiconductor laser based on beam expansion of the present invention, the final output laser light distribution is a flat-top distribution, and the energy distribution is uniform.

Description of drawings

Fig. 1 is a schematic diagram of the present invention;

Fig. 2 is a schematic diagram of Embodiment 1 of the present invention;

Fig. 3 is a schematic diagram of Embodiment 2 of the present invention;

Figure 4 is a schematic diagram of Embodiment 3 of the present invention;

Fig. 5 is a schematic diagram of Embodiment 4 of the present invention.

Description of reference numerals: 1 is a semiconductor laser; 2 is a collimating lens group; 3 is a beam splitting system; 4 is a focusing system; 5 is a beam splitter; 6 is a reflector; 7 is a fast axis collimating lens; 8, 9 are focusing lenses ; 10 is the output spot; 11 is the slow axis collimator; 12 is the light splitting surface; 13 is the light output surface; 14 is the reflection surface; 15 is the light splitting module;

detailed description:

As shown in Figure 1, the high-power semiconductor laser optical device based on beam expansion includes a semiconductor laser stack 1, a collimating lens group 2, a beam splitting system 3 and a focusing system 4.

The semiconductor laser stack 1 is composed of several semiconductor laser units; the collimating lens group 2 is placed at the laser exit of the semiconductor laser; The collimated laser beam is expanded; the focusing system 4 is used to focus and shape the expanded laser beam.

The light splitting system 3 includes n components of optical modules, as shown in Figure 1, in this embodiment, it is a group of optical modules, the light splitting module includes a beam splitter 5 and a reflector 6, and the laser light emitted by the laser is incident on the beam splitter 5; , the beam splitting surface of the beam splitter and the reflection surface of the reflector are set parallel to each other along the height direction and form an angle of 30-60° with the laser light output direction, preferably 30°, 45°, 55°, 60° angle setting, the beam splitter 5. Transmit half of the light, and half of the light is reflected by 90 degrees and then enters the reflector 6. After being reflected by the reflector 6 again by 90 degrees, it is combined with the light transmitted by the beam splitter 5 and then enters the focusing system 4 to output a spot 10. .

The transmittance of the beam splitter 5 is 50%, and the reflectivity is 50%; the reflectivity of the reflector 6 is 100%, and the reflector 6 can be a total reflection mirror, a total reflection prism, or a polarizing device , can be a polarizer, a polarizer or a polarization beam combiner.

As shown in Figure 2, the high-power semiconductor laser optical device based on beam expansion includes a semiconductor laser stack 1, a collimating lens group 2, a beam splitting system 3 and a focusing system 4. The semiconductor laser stack 1 is composed of several semiconductor laser units; the collimating lens group 2 is placed at the laser exit of the semiconductor laser stack 1; the beam splitting system 3 is placed in the laser beam exit direction after collimation , including n component optical modules 15, each component optical module 15 includes a beam splitter 5 and a reflector 6, the light beam emitted by the mth ((1≤m<n) component optical module is incident on the m+1th component optical module 3 on the beam splitter.

As shown in Figure 2, the transmittance of the beam splitter 6 is 50%, and the reflectivity is 50%; the reflectivity of the reflector 7 is 100%, and the reflector 7 can be a total reflection prism or a polarizing device, Specifically, it may be a polarizer, a polarizer or a polarization beam combiner.

The beam splitter 6 adopts a beam splitter, the base material is glass, the surface of the beam splitter is coated with a semi-transparent and semi-reflective film, and the material of the semi-transparent and semi-reflective film is zinc sulfide-magnesium fluoride film system; the reflector is a total reflection plane mirror, The base material is glass or metal, and the surface is coated with a high-reflection film; the material of the high-reflection film is metallic silver or aluminum, or the high-reflection film adopts a multilayer dielectric reflective film.

As shown in Figure 3, the light splitting module uses a combination of parallelepiped prism and triangular prism to realize the functions of beam splitter 6 and reflector 7 as a whole. The incident surface 16 of the light-splitting module is closely attached to the triangular prism on the adjacent side of the acute angle with the side. The adjacent side with an obtuse angle is used as the reflective surface 14 of the reflector; the triangular prism also has an outer surface perpendicular to the light emitting direction of the laser, which is used as the light emitting surface 13 of the light splitting module.

As long as the light splitting module realizes that the second half of the light of the laser beam passes through the semi-transparent and semi-reflective surface, that is, the splitting surface 12, it is transmitted to the transmission surface, that is, the light-emitting surface 13 for transmission, and the other half of the light is transmitted to the reflective surface 14 for total reflection, and then the beams are combined and emitted to realize the expansion. bundle.

The beam splitter 5 and the reflector 6 adopted by the light splitting module are parallelepiped prisms (included angles of 45° and 135°) and triangular prisms used in combination to realize laser beam expansion, that is, the semi-transparent and semi-reflective surfaces of the parallelepiped prisms, that is, the splitting surface 12 and The semi-transparent and semi-reflective surface of the triangular prism, that is, the light-splitting surface 12 is closely attached; the semi-transparent and semi-reflective surface of the parallelepiped prism, that is, the light-splitting surface 12 is coated with a semi-transparent and semi-reflective film, and the semi-transparent and semi-reflective surface of the triangular prism, that is, the light-splitting surface 12 is coated with a semi-transparent and semi-reflective film. ; The reflective surface 14 of the parallelepiped prism is coated with a reflective film, and the transmissive surface of the triangular prism, that is, the light-emitting surface 13 is coated with a transmissive film.

Parallelepiped prism and triangular prism can not be one piece, if one piece then semi-transparent and semi-reflective surface will not be able to realize the semi-transparent and semi-reflective effect.

As shown in Figure 3, in addition to using a triangular prism, other irregular devices can also be used, as long as the semi-transparent and semi-reflective surface of the device, that is, the splitting surface 12, can realize half of the light transmission, half of the light reflection and its transmission surface, that is, the light-emitting surface 13, can directly The light is transmitted vertically.

Fig. 4 is a schematic diagram of Embodiment 3 of the present invention, based on the high-power semiconductor laser optical device of beam expansion, including a semiconductor laser array 1, a collimating lens group 2, a beam splitting system 3 and a focusing system 4 arranged in sequence along the optical path, and the semiconductor laser The laser light emitted by stack 1 is collimated, expanded by beam splitting system 3 , enters focusing system 4 , and outputs light spot 10 .

The beam splitting system 3 includes n beam splitters 5 sequentially arranged along the stack height direction of the semiconductor laser stack 1 and a reflector 6 arranged at the end, wherein the first beam splitter 5 is equivalent to the stack height of the semiconductor laser stack, and n The beam splitter and the reflector 6 are arranged in parallel and at equal intervals, forming a certain angle with the semiconductor laser stack light output direction, usually between 30-60 degrees, preferably 45 degrees, 60 degrees, etc.; the transmitted light of the first beam splitter 5 and the rest The reflected light of n-1 beam splitters 5 and reflectors 6 together form laser beam expansion;

The light transmittance of the n beam splitters 5 is different, and the transmitted light energy of the first beam splitter 5 is equal to the reflected light energy of the remaining n-1 beam splitters 5 and reflectors 6:

The transmittance of the first beam splitter is 1/(n+1), and the reflectance is n/(n+1);

The transmittance of the mth beam splitter is (n-m+1)/(n-m+2), and the reflectance is 1/(n-m+2);

Wherein, n is the total number of beam splitters, m is the sequence number of the beam splitters, 1<m≤n.

The semiconductor laser beam expander shown in Figure 4 is a trial-manufactured laser processing system for laser welding circuit boards. It requires a laser array with a power of 400W (4 bars) and a uniform spot at 120mm of laser output, which is equivalent to The height of the laser stack and the focal length of the lens are limited. If you directly use a convex lens for focusing, you will eventually get 4 strong spots distributed at intervals, which cannot meet the requirements. In combination with the present invention, the specific implementation is: as shown in Figure 4, after the semiconductor laser stack 1, the beam expander mentioned in the present invention is added, and then the convex lens is used for focusing, which is equivalent to increasing the size of the light-emitting surface output by the laser stack , improve the compression ratio of the beam, and finally get a uniform spot. This method does not need to increase the laser bar, saves the cost, and effectively improves the spot quality.

5 is a schematic diagram of Embodiment 4 of the present invention. Another beam expander device for high-power semiconductor lasers of the present invention includes a semiconductor laser array 1, a collimating lens group 2, a beam splitting system 3 and a focusing system 4 arranged in sequence along the optical path. The laser light emitted by the semiconductor laser stack 1 is collimated, expanded by the beam splitting system 3 , enters the focusing system 4 , and outputs a light spot 10 .

The beam splitting system 3 includes n beam splitters 5 sequentially arranged along the light emitting direction of the semiconductor laser stack 1 and a reflector 6 arranged at the end, wherein the first beam splitter 5 is equivalent to the stack height of the semiconductor laser stack 1, and the n beam splitters 5 and the reflectors 6 are arranged in parallel and at equal intervals, forming a certain angle with the semiconductor laser stacked light output direction, usually between 30-60 degrees, preferably 45 degrees, 60 degrees, etc.; the reflected light of n beam splitters 5 and reflectors is common form laser beam expansion;

The light transmittance of the n beam splitters is different, so that the reflected light energy of the n beam splitters and the total reflection mirror is equal:

The reflectance of the mth beam splitter is 1/(n-m+2), and the transmittance is (n-m+1)/(n-m+2);

Wherein, n is the total number of beam splitters, m is the sequence number of the beam splitters, 1≤m≤n.

In the present invention, after the laser beam emitted by the stack of semiconductor lasers is expanded by the beam splitting system, the laser beam whose energy distribution is Gaussian distribution is converted into a flat-top beam with uniform energy density distribution in the direction of the fast axis. The laser is focused to improve the uniformity of the spot, which can achieve the uniformity of the spot and achieve a uniform planar spot output. However, with the traditional method, due to the spacing between the bars in the stack of semiconductor lasers, stripe-shaped spots will always be formed.

Claims (4)

1. A high-power semiconductor laser optical shaping device based on beam expansion, characterized in that: comprise a stack of semiconductor lasers, a collimating lens group, a beam splitting system and a focusing system arranged successively along the optical path, and the stack of semiconductor lasers is composed of Composed of several semiconductor laser units; the light splitting system includes n components of optical modules arranged in sequence along the laser light emitting direction, each group of optical modules includes a beam splitter and a reflector, and the beam splitting surface of the beam splitter and the reflecting surface of the reflector are arranged along the height direction Parallel to each other and form an angle of 30-60° with the laser light output direction; after the laser beam passes through the beam splitter, half of the energy of the light is directly transmitted, and the other half of the energy of the light is reflected to the reflector and then reflected again, and the light directly transmitted by the beam splitter Parallel exit; The beam splitter of the first component optical module is equivalent to the stacking height of the semiconductor laser stack; the size of each component optical module is multiplied sequentially, and the light beam emitted by the mth component optical module is incident on the beam splitter of the m+1th component optical module, 1 ≤m<n, m is the sequence number of the light splitting module, and the sequence number is arranged according to the order in which the laser passes through; the focusing system is used to focus and reshape the beam expanding laser to obtain a spot of required size; The light-splitting module adopts a combination of a parallelepiped prism and a triangular prism to realize the functions of a beam splitter and a reflector as a whole. The parallelepiped prism has the only side facing the stack of semiconductor lasers and is perpendicular to the light-emitting direction of the laser as the light-incidence surface of the light-splitting module. The triangular prism is closely attached to the adjacent side that the included angle with the side is an acute angle. The reflective surface of the reflector; the triangular prism also has an outer surface perpendicular to the light emitting direction of the laser, which serves as the light emitting surface of the light splitting module. 2. The high-power semiconductor laser optical shaping device based on beam expansion according to claim 1, characterized in that: the beam splitting surface of the beam splitter and the reflecting surface of the reflector are all set at an angle of 45° to the laser light emitting direction. 3. A high-power semiconductor laser optical shaping device based on beam expansion, characterized in that: it comprises a semiconductor laser array, a collimating lens group, a beam splitting system and a focusing system arranged in sequence along the optical path, and the beam splitting system includes a semiconductor laser array along the optical path. N beamsplitters and a total reflection mirror are arranged in sequence in the direction of the stack height of the array, wherein the first beam splitter is equivalent to the stack height of the semiconductor laser array, and the n beamsplitters and total reflection mirrors are arranged in parallel and equally spaced. The direction of light output from the semiconductor laser stack is set at 30-60°; the transmitted light of the first beam splitter and the reflected light of the remaining n-1 beam splitters and the total reflection mirror together form a laser beam expansion; the focusing system is used for The expanded laser beam is focused and shaped to obtain the desired size of the spot; The light transmittance of the n beamsplitters is different, and the transmitted light energy of the first beamsplitter is equal to the reflected light energy of the remaining n-1 beamsplitters and the total reflection mirror: The transmittance of the first beam splitter is 1/(n+1), and the reflectance is n/(n+1); The transmittance of the mth beam splitter is (n-m+1)/(n-m+2), and the reflectance is 1/(n-m+2); Among them, n is the total number of beam splitters, m is the sequence number of the beam splitter, 1<m≤n, and the sequence numbers are arranged according to the order in which the laser light passes through. 4. A high-power semiconductor laser optical shaping device based on beam expansion, characterized in that: it comprises a semiconductor laser array, a collimating lens group, a beam splitting system and a focusing system arranged successively along the optical path, and the semiconductor laser array consists of several Composed of stacked semiconductor laser units, the beam splitting system includes n beam splitters arranged in sequence along the light output direction of the semiconductor laser stack and a total reflection mirror at the end, wherein the first beam splitter is equivalent to the stack height of the semiconductor laser stack, n beamsplitters and total reflection mirrors are arranged in parallel and at equal intervals, and are arranged at 30-60° with the light emitting direction of the semiconductor laser array; the reflected light of n beamsplitters and total reflection mirrors together form laser beam expansion; the focusing system is used Focusing and shaping the expanded laser beam to obtain the desired size of the spot; The light transmittance of the n beamsplitters is different, so that the reflected light energy of the n beamsplitters and the total reflection mirror is equal: The reflectance of the mth beam splitter is 1/(n-m+2), and the transmittance is (n-m+1)/(n-m+2); Among them, n is the total number of beam splitters, m is the array number of beam splitters, 1≤m≤n, and the array numbers are arranged according to the order in which the laser light passes through.