A multi-channel laser color separation and beam combining module and its adjustment method

Abstract

The present invention discloses a multi-channel laser color separation and beam combining module and its adjustment method, which comprises a beam combining body (1), wherein the beam combining body (1) is an optical monomer, wherein a plane on one side of the beam combining body (1) is an incident surface (2), and an opposite plane parallel to the incident surface (2) is divided into an exit surface (4) located at one end and a reflection surface (3) outside the exit surface (4); the incident surface (2) is divided into N coating areas, and the surfaces of the N coating areas are correspondingly provided with color separation medium films with different high reflection coefficients, and the surface of the reflection surface (3) is provided with a broadband high reflection medium film; and the surface of the exit surface (4) is provided with a broadband anti-reflection film. The multi-channel laser color separation and beam combining module provided by the present invention is an integrated type, and according to its adjustment method, it can realize high-quality synthesis of multiple lasers with different wavelengths, and has the outstanding advantages of good optical axis stability and compact optical path layout, and can be used for high-stability and high-precision synthesis of multiple lasers with different wavelengths.

Description

Technical Field

[0001] The present invention relates to the technical field of laser synthesis, and in particular to a multi-channel laser color separation and beam combining module and an adjustment method thereof. Background Art

[0002] Laser synthesis technology plays an important role in improving laser output power and expanding the laser working wavelength range. At present, laser synthesis technology mainly includes two technical routes: coherent synthesis and incoherent synthesis. Among them, coherent synthesis has very high requirements on the coherence of each laser involved in the synthesis, and requires complex closed-loop control, which is technically complex. Therefore, the laser synthesis technology currently used in the field of laser technology mostly adopts color separation synthesis. That is, through the design and preparation of the color separation lens film system, one wavelength laser is highly reflected by the color separation plate, and the other wavelength laser is highly transparent by the color separation plate. The two laser beams are synthesized into one laser beam, and then the same technical principle is used again. After passing through another color separation mirror, it is synthesized with the third laser beam. By analogy, multiple color separation mirrors can be used to synthesize multiple wavelength lasers into one laser output, thereby expanding the power of the output laser and widening the wavelength band.

[0003] However, in actual engineering, since each lens is designed independently, affected by ambient temperature changes and vibrations, the lenses may be misaligned in different directions, resulting in relative changes in the output optical axes of lasers of different wavelengths, affecting the output beam quality. At the same time, under high-power working conditions, since the power borne by each mirror is inconsistent, each mirror will produce different dynamic angle deviations, which will also cause dynamic changes in the optical axes of lasers of different wavelengths involved in the synthesis, resulting in obvious spot expansion of the synthesized laser in the far field (surface of the object), reducing the output beam quality and affecting the use effect. Summary of the invention

[0004] In order to overcome the above technical problems, the purpose of the present invention is to provide a multi-channel laser color separation and beam combining module and its adjustment method. The beam combining module has high optical axis stability and high output beam quality, and combines multi-channel color separation lasers into a high-quality beam, which is suitable for the field of high-power laser synthesis technology.

[0005] The present invention provides the following technical solutions:

[0006] A multi-channel laser color separation beam combining module, comprising a beam combining body (1), the beam combining body (1) being an optical monomer; a plane on one side of the beam combining body (1) being an incident surface (2), and an opposite plane parallel to the incident surface (2) being divided into an exit surface (4) located at one end and a reflection surface (3) outside the exit surface (4);

[0007] The incident surface (2) is divided into N coating areas, and N laser beams are incident on the beam combining body (1) from the corresponding N coating areas, wherein the incident angle of the i-th collimated laser beam with the incident surface (2) is α i , where N is a natural number greater than or equal to 1, i is a natural number greater than or equal to 1 and less than or equal to N; Δλi is the spectral width of the i-th laser, λ i is the central wavelength of the i-th laser; a color separation medium film is provided on the surface of the i-th coating area corresponding to the i-th laser, and the color separation medium film of the i-th coating area has a wavelength range greater than or equal to λ i -Δλ i / 2 and less than or equal to λ i +Δλ i / 2 incident laser is highly transparent and has a wavelength less than λ i -Δλ i / 2 laser high reflection;

[0008] A broadband high-reflection dielectric film is provided on the surface of the reflection surface (3);

[0009] A broadband anti-reflection film is provided on the surface of the emission surface (4).

[0010] In the above embodiment, the beam combining module is an optical monomer structure as a whole, and the incident angle between the i-th laser and the incident surface (2) is α i The i-th coating area corresponding to the i-th collimated laser is coated with dichroic dielectric films with different high reflection coefficients, and dichroic dielectric films with different high reflection coefficients are set to achieve high transmittance or high reflection for lasers of different wavelengths. The broadband high reflection dielectric film is used to highly reflect the laser directed to the reflection surface, and the laser is emitted from the exit surface.

[0011] Furthermore, the beam combining body (1) is an optical monomer, and the volume absorption coefficient of the optical monomer for each wavelength laser involved in the synthesis is less than 0.02 / cm.

[0012] Furthermore, after the i-th laser beam is incident on the beam combining body (1), the refraction angle between the i-th laser beam and the incident surface (2) is β i , the spot diameter of the i-th laser is d i ,

[0013] The width W of the beam combining body (1) satisfies: W>max{d i / (cosα i tanβ i )};

[0014] The length L of the beam combining body (1) satisfies: L>N×max{d i / cosα i};

[0015] The height H of the beam combining body (1) satisfies: H>max{d i}.

[0016] Furthermore, the N coating areas are N equally divided areas of the incident surface (2) along the length L.

[0017] Furthermore, the length of the exit surface (4) is L1, L1>max{d i}.

[0018] Furthermore, the laser medium film coated in the i-th coating area has a high sensitivity to the incident laser λ i Transmittance is greater than 97% for wavelengths less than λ i -Δλ i The laser reflectivity of / 2 is greater than 99%.

[0019] Furthermore, the reflectivity of the broadband high-reflective dielectric film is greater than 98%.

[0020] Furthermore, the broadband antireflection film on the surface of the exit surface (4) has a transmittance greater than 99% for lasers with a wavelength of λi.

[0021] Furthermore, the beam combining body is a cuboid.

[0022] The present invention also provides a method for adjusting a multi-channel laser color separation and beam combining module, which adjusts the incident angle α of the i-th laser channel. i The adjustment steps include:

[0023] S1: a telephoto lens (7) is arranged outside the exit surface (4), and the optical axis of the telephoto lens (7) is collinear with the optical axis of the exit laser;

[0024] S2: placing a photoelectric detection device (8) at the focal plane of the telephoto lens (7);

[0025] S3: Adjust the incident angle α of the i-th laser beam by observing the center of the light spot on the focal plane of the telephoto lens (7) i , so that the centers of the laser light spots of each output path are located at the same imaging pixel position of the photoelectric detection device (8);

[0026] S4: Fix the angle of the i-th incident laser beam.

[0027] In the above embodiment, the photoelectric detection device is selected from one of a four-quadrant sensor, a CCD or a CMOS imaging device.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The multi-channel laser color separation and beam combining module is integrated with simple structure, and can realize high-quality synthesis of multiple lasers with different wavelengths. It has the outstanding advantages of good optical axis stability and compact optical path layout. It can be used for high-stability and high-precision synthesis of multiple lasers with different wavelengths, has good output beam quality, and significantly improves the long-term stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the multi-channel laser color separation and beam combining module provided by the present invention.

[0031] Figure 2 This is a schematic diagram of an embodiment of a multi-channel laser color separation and beam combining module provided by the present invention.

[0032] Figure 3 A schematic diagram of an adjustment method for a multi-channel laser color separation and beam combining module provided by the present invention.

[0033] Figure 4 This is a multi-view schematic diagram of Example 1 provided by the present invention.

[0034] The reference numerals in the accompanying drawings are:

[0035] 1. Beam combining body; 2. Incident surface; 3. Reflection surface; 4. Exit surface; 5. Two-dimensional adjustable optical frame; 6. Laser collimator; 7. Telephoto lens; 8. Photoelectric detection device. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the embodiments and drawings, but it should be understood that the embodiments and drawings are only used to exemplify the present invention and do not constitute any limitation on the protection scope of the present invention. All reasonable changes and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0037] The present invention will be further described below in conjunction with the accompanying drawings.

[0038] like Figure 1 The basic principle of the present invention is shown as follows: multiple collimated lasers with different wavelengths enter the beam combining module from the corresponding coating areas at corresponding incident angles, and are selectively highly transmitted or reflected between the reflection surface 3 and the incident surface 2 of the beam combining module. After the Nth laser is combined with the previous N-1 lasers at the incident surface 2, they are transmitted to the exit surface 4 to realize the combined laser output of the beam combining module.

[0039] like Figure 2As shown in the figure, the beam combining body 1 of the multi-channel laser color separation and beam combining module is a rectangular optical monomer, the left plane of which is the incident surface 2, the upper side of the right plane parallel to the left plane is the reflection surface 3, and the lower side is provided with an exit surface 4; the incident surface 2 is evenly divided into 5 coating areas from top to bottom, and the number of laser beams and coating areas in the figure are both 5. The 5 laser beams are arranged from top to bottom, and are incident into the interior of the beam combining body 1 from the corresponding coating areas, respectively, where the central wavelength of the i-th laser is λ i , the incident angle of the i-th laser beam to the incident surface 2 is set to α i , Δλ i is the spectral width of the i-th laser, where i is a natural number between 1 and 5; a dichroic dielectric film is coated on the i-th coating area corresponding to the i-th laser, and the wavelength range of the dichroic dielectric film for the incident laser is greater than or equal to λ i -Δλ i / 2 and less than or equal to λ i +Δλ i / 2 incident laser is highly transparent and has a wavelength less than λ i -Δλ i / 2 laser high reflection; the surface of the reflection surface 3 is coated with a broadband high reflection dielectric film, which is highly reflective to lasers; the exit surface 4 is coated with a high reflection dielectric film for wavelength λ i Broadband anti-reflection film with a transmittance greater than 99%. The beam combining body 1 is optically processed and the laser incident surface 2, reflection surface 3 and output surface 4 are coated in different regions, and lasers of different wavelengths can be selectively highly transparent or reflected to achieve the purpose of color separation and beam combining of multiple lasers.

[0040] Based on the above structure, N collimated lasers with different wavelengths are respectively incident on the corresponding i-th coating area at corresponding incident angles α. i After entering the beam combining body 1, the Nth laser beam is reflected between the reflection surface 3 and the incident surface 2, and after being combined with the first N-1 beam beams at the incident surface 2, it is transmitted to the exit surface 4 to realize the combined laser beam outputting the beam combining body 1. Wherein, N is a natural number greater than or equal to 1, and i is a natural number greater than or equal to 1 and less than or equal to N.

[0041] More specifically, the central wavelength of the i-th laser is λ i , more than 90% of the energy falls on wavelengths greater than or equal to λ i -Δλ i / 2 and less than or equal to λ i +Δλ i / 2 range, Δλ i is the spectral width of the i-th laser; the spot diameter of the i-th laser is d i .

[0042] The optical monomer is made of monomer optical material. The monomer optical material has a wavelength of λ iThe laser body absorption coefficient is less than 0.02 / cm to ensure that the beam combining body 1 does not produce excessive thermal expansion.

[0043] After the i-th laser beam is incident into the beam combining body 1, its refraction angle with the incident surface 2 is β i ; The spot diameter of the i-th laser is d i ;

[0044] The incident angle of the i-th laser beam at the incident surface 2 is α i , after incident on the monomer beam combining module, its refraction angle is β i , we can get:

[0045] sinβ i = sinα i / n i

[0046] Where n i For the monomer optical material, the center wavelength of the i-th path is λ i The refractive index of the laser.

[0047] Among them, the width W of the beam combining body 1 satisfies: W>max{d i / (cosα i tanβ i )};

[0048] The length L of the beam combining body 1 satisfies: L>N×max{d i / cosα i};

[0049] The height H of the beam combining body 1 satisfies: H>max{d i}.

[0050] Figure 2 In the figure, the beam combining body 1 has a width W along the Y-axis direction, a length along the Z-axis direction, and a height H along the X-axis direction.

[0051] The laser dielectric film can be deposited in N times, and each time the rest of the incident surface 2 is shielded in the coating machine, so that the laser dielectric film deposited in the i-th area is sensitive to the incident laser λ i Transmittance is greater than 97%, for wavelengths less than λ i -Δλ i The laser reflectivity of / 2 is greater than 99%.

[0052] The reflective surface 3 is coated with a high-reflective dielectric film to achieve high reflectivity for all wavelengths of the combined laser beam, and the reflectivity of the high-reflective dielectric film is greater than 98%.

[0053] The exit surface 4 and the reflection surface 3 are located on the same plane. After the Nth laser beam is combined with the first N-1 beam beams at the incident surface 2, it is transmitted to the exit surface 4 to realize the combined laser output. The length of the exit surface 4 is L1, where L1>max{di}. This area is plated for λ i (i=1~N) The film system with a transmittance greater than 99% can achieve combined beam laser output.

[0054] After different wavelength lasers with the same incident angle pass through the beam combiner 1, due to the slight difference in the refractive index of the optical material for lasers of different wavelengths, mainly the dispersion effect and the processing wedge angle error when processing the optical monomer beam combiner 1, this error causes the angle γ between the incident surface 2 and the reflection surface 3, and the final emission angle of lasers of different wavelengths on the output surface has a slight difference. Therefore, in actual engineering manufacturing, the incident angle α of the i-th laser can be precisely adjusted. i , so that the optical axes of lasers with different wavelengths remain consistent at the output surface 4 of the beam combining module.

[0055] The present invention also provides a method for adjusting a multi-channel laser color separation and beam combining module, such as Figure 3 As shown, the method for precisely adjusting the incident angle of the i-th collimated laser includes the following steps:

[0056] S1: a telephoto lens is arranged outside the exit surface 4, and the optical axis of the telephoto lens 7 is collinear with the optical axis of the first exit laser;

[0057] S2: placing a photoelectric detection device 8 at the focal plane of the telephoto lens 7;

[0058] S3: Precisely adjust the incident angle α of the i-th laser beam by observing the center of the light spot on the focal plane of the telephoto lens 7 i , so that the center of each outgoing laser spot is located at the same imaging pixel position of the photoelectric detection device 8;

[0059] S4: After the incident angle is precisely adjusted, the angle of the i-th incident laser beam is fixed.

[0060] The photoelectric detection device 8 is selected from the existing four-quadrant sensor, CCD or CMOS imaging device; the focal length of the telephoto lens 7 is selected from an aberration-free lens with a focal length greater than 1m; the method for fixing the angle of the incident laser beam can be selected from gluing or mechanical locking. Repeat the above adjustment method until the incident angle of all laser beams is precisely adjusted. After the adjustment is completed, the telephoto lens 7 and the photoelectric detection device 8 are removed.

[0061] The method of precisely adjusting the incident laser angle is a well-known method in the industry. For example, the existing two-dimensional adjustable optical frame 5 can be used to adjust the incident laser beam incident angle.

[0062] Embodiment 1:

[0063] like Figure 4 Figure a is the front view, Figure b is the left view, Figure c is the top view, and Figure d is the isometric view. The five fiber lasers involved in the synthesis have wavelengths of 1056nm, 1062nm, 1068nm, 1074nm, and 1080nm, and the spectrum width of each laser is 2nm. Each fiber laser is connected to the industrial end cap and laser collimator 6 via a pigtail, and the diameter of the beam emitted by the laser collimator 6 is d i =10mm; the collimating beam expander is clamped by a two-dimensionally adjustable optical frame 5 and installed on the same substrate. The two-dimensionally adjustable optical frame 5 is arranged in order from long-wave band to short-wave band along the X-axis, which are 1080nm, 1074nm, 1068nm, 1062nm, and 1056nm lasers. Through mechanical installation and preliminary adjustment of the two-dimensionally adjustable optical frame 5, the optical axes of the five output light beams are parallel to the Z direction of the substrate, and the height of each laser output optical axis to the XOZ plane is 25mm, and the optical axis spacing is 50mm.

[0064] The beam combining body 1 is made of Corning 7980 quartz material, which has a very small volume absorption coefficient for 1 μm to 1.1 μm lasers; its dimensions are: width W = 80 mm, height H = 50 mm, and length L = 250 mm.

[0065] The incident surface 2, the reflection surface 3 and the output surface 4 on the beam combining module are processed into planes, and the PV value of the surface accuracy is better than 0.1λ, where λ is the shortest wavelength involved in the synthesis, that is, λ=1056nm, and the angle between the two planes is less than 3 arc seconds.

[0066] The incident surface 2 of the beam combining module is divided into five equal areas along the length L direction, and the coating is carried out in order from short wave to long wave. The size of each coating area is 50mm×50mm. When coating each area, other areas need to be protected to avoid affecting the transmittance / reflectivity of other areas during coating.

[0067] The requirements for the coating system in area 1 are: the transmittance at 1055nm to 1057nm is greater than 99%;

[0068] The requirements for the coating system in area 2 are: the transmittance at 1061nm to 1063nm is greater than 99%; the reflectivity at 1055nm to 1057nm is greater than 99%;

[0069] The requirements for the coating system in area 3 are: the transmittance at 1067nm to 1069nm is greater than 99%; the reflectivity at 1055nm to 1063nm is greater than 99%;

[0070] The requirements for the coating system in area 4 are: the transmittance at 1073nm to 1075nm is greater than 99%; the reflectivity at 1055nm to 1069nm is greater than 99%;

[0071] The requirements for the coating system in area 5 are: the transmittance at 1079nm to 1081nm is greater than 99%; the reflectivity at 1055nm to 1075nm is greater than 99%;

[0072] The coating requirements for the reflective surface 3 are: the reflectivity from 1055nm to 1081nm is greater than 99%;

[0073] The requirements for the coating on the output surface 4 are: the transmittance from 1055nm to 1081nm is greater than 99%;

[0074] A beam combining module installation area with a 1mm depression is processed on the XOZ surface of the substrate. The size is 250mm (L) × 80mm (W), and the angle between its long side L and the Z axis is 80°. The beam combining module is installed in this concave installation area so that the incident surface 2 faces the direction of the incoming light, and the lasers of different wavelengths are incident on the corresponding high-transmittance coating area. The beam combining module is fixed by mechanical clamping or gluing. This ensures that the initial incident angle of the five lasers on the incident surface 2 of the beam combining module is 10°.

[0075] A telephoto lens 7 with a focal length of 1m is set on the exit surface 4, so that the 1056nm wavelength laser is incident on the telephoto lens 7, and a focal spot is formed at the focal plane of the telephoto lens 7. An inclined reflector and attenuation plate are used in front of the telephoto lens 7 to attenuate the laser, so that the laser power at the focal plane is less than 1mW. A CMOS camera or a commercial spot analyzer is installed at the focal plane to collect the spot morphology and calculate the pixel coordinates (X0, Y0) of the spot centroid position on the camera, and the coordinate data is recorded as the reference for fine-tuning the incident angles of the other 4 lasers.

[0076] The two-dimensional tilt adjustment knobs of the remaining four optical adjustment frames are fine-tuned in sequence so that the centroids of the light spots of the remaining four lasers are all at the (X0, Y0) position. This indicates that the output optical axes of the five lasers have been adjusted with high precision.

[0077] Remove the reflector, attenuation plate, telephoto lens 7 and CMOS camera, and start 5 lasers at the same time. The laser emitted from the output surface 4 of the beam combining module is a single laser beam formed by combining five lasers with different wavelengths.

[0078] Due to the existence of dispersion, the initial incident angle α can be calculated based on the pixel coordinates of each monitored light spot on the focal plane. i are first set to 10°, and then according to the incident angle α of the i-th laser i Adjust the steps for fine adjustment.

[0079] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A multi-channel laser color separation and beam combining module, characterized in that: It comprises a beam combining body (1), wherein the beam combining body (1) is an optical monomer; a plane on one side of the beam combining body (1) is an incident surface (2), and an opposite plane parallel to the incident surface (2) is divided into an exit surface (4) located at one end and a reflection surface (3) outside the exit surface (4); The incident surface (2) is divided into N coating areas, and N laser beams are incident on the beam combining body (1) from the corresponding N coating areas, wherein the incident angle of the i-th collimated laser beam with the incident surface (2) is α i , where N is a natural number greater than or equal to 1, and i is a natural number greater than or equal to 1 and less than or equal to N; Δλ i is the spectrum width of the i-th laser, λ i is the central wavelength of the i-th laser; The surface of the i-th coating area corresponding to the i-th laser is provided with dichroic dielectric films with different high reflection coefficients. The dichroic dielectric films in the i-th coating area have a wavelength range greater than or equal to λ i -Δλ i / 2 and less than or equal to λ i +Δλ i / 2 incident laser is highly transparent and has a wavelength less than λ i -Δλ i / 2 incident laser high reflection; A broadband high-reflection dielectric film is provided on the surface of the reflection surface (3); A broadband anti-reflection film is provided on the surface of the emission surface (4).

2. The multi-channel laser color separation and beam combining module according to claim 1, characterized in that: The beam combining body (1) is an optical monomer, and the volume absorption coefficient of the optical monomer for each wavelength laser involved in the synthesis is less than 0.02 / cm.

3. The multi-channel laser color separation and beam combining module according to claim 1, characterized in that: After the i-th laser beam is incident on the beam combining body (1), the refraction angle between the laser beam and the incident surface (2) is β i , the spot diameter of the i-th laser is d i , The width W of the beam combining body (1) satisfies: W>max{d i / (cosα i tanβ i )}; The length L of the beam combining body (1) satisfies: L>N×max{d i / cosα i }; The height H of the beam combining body (1) satisfies: H>max{d i }.

4. The multi-channel laser color separation and beam combining module according to claim 3, characterized in that: The N coating areas are N equally divided areas of the incident surface (2) along the length L.

5. The multi-channel laser color separation and beam combining module according to claim 3, characterized in that: The length of the exit surface (4) is L1, L1>max{d i }.

6. The multi-channel laser color separation and beam combining module according to claim 1, characterized in that: The color separation medium film coated in the i-th coating area has a high sensitivity to the incident laser λ i The transmittance is greater than 97%, and the wavelength is less than λ i -Δλ i The laser reflectivity of / 2 is greater than 99%.

7. The multi-channel laser color separation and beam combining module according to claim 1, characterized in that: The broadband high reflective dielectric film has a wavelength of λ i The reflectivity of the laser is greater than 98%.

8. The multi-channel laser color separation and beam combining module according to claim 1, characterized in that: The broadband antireflection film on the surface of the exit surface (4) has a wavelength of λ i The laser transmittance is greater than 99%.

9. The multi-channel laser color separation and beam combining module according to claim 1, characterized in that: The beam combining body (1) is a rectangular parallelepiped.

10. The method for adjusting a multi-channel laser color separation and beam combining module according to any one of claims 1 to 9, characterized in that: For the i-th laser incident angle α i The adjustment steps include: S1: a telephoto lens (7) is arranged outside the exit surface (4), and the optical axis of the telephoto lens (7) is collinear with the optical axis of the exit laser; S2: placing a photoelectric detection device (8) at the focal plane of the telephoto lens (7); S3: Adjusting the incident angle α of the i-th laser beam by observing the center of the light spot on the focal plane of the telephoto lens (7) i , so that the centers of the laser light spots of each output path are located at the same imaging pixel position of the photoelectric detection device (8); S4: Fix the angle of the i-th incident laser beam.

Images