A spliced double-grating spectrum synthesis device and method

Abstract

The application belongs to the technical field of high-power laser spectrum synthesis, and particularly relates to a spliced double-grating spectrum synthesis device and method. The device comprises a spliced grating, a spliced grating clamp, an output grating and an output grating clamp. The spliced grating is composed of a plurality of sub-gratings with the same linear density and is spliced in parallel along the direction perpendicular to the grating lines. The parallel incident light beam array is diffracted to the same point on the surface of the output grating, and then the multiple wavelength light beams are diffracted to the same direction by the output grating to realize the double-grating spectrum beam synthesis. The spliced grating spectrum synthesis device and method can effectively expand the incident grating aperture, can carry more incident light beams, can realize higher-power spectrum synthesis output power, and can maintain good beam quality, and has important application reference value in the field of high-power laser technology.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-power laser spectrum synthesis, in particular to a splicing type double-grating spectrum synthesis device and method, which is suitable for the fields of industrial processing, national defense technology and scientific research that need high-power and high-beam quality laser output. BACKGROUND

[0002] High-power laser technology has important applications in industrial manufacturing, national defense security, and basic scientific research. However, due to the limitations of laser technology and material technology, the output power of a single laser is far from meeting the application requirements, so it is necessary to use multi-beam laser combination technology to combine and amplify the power. Spectral combination technology can realize multi-beam co-aperture combination, greatly improve the output power, and maintain good beam quality, and is one of the most important power improvement routes. However, due to the existence of a certain linewidth of the laser, the beam quality deteriorates after grating dispersion, therefore, the double-grating spectral combination scheme is often used to suppress the dispersion effect

Prior Art 1: P. Madasamy, et al., Dual-Grating Spectral Beam Combination of High-Power Fiber Lasers, IEEE J. Sel. Top. Quantum Electron. 15(2), 337-343 (2009)

Prior Art 2: Zheng Y, et al., 10.8 kW spectral beam combination of eight all-fiber superfluorescent sources and their dispersion compensation, Opt. Express 24(11), 12063-12071 (2016)

Prior Art 3: Zheng Y, et al., Twenty kilowatts level high beam quality spectral beam combination by dual gratings with distinct groove densities based on conical diffraction structures, Opt. Express 32(24), 43076-43086 (2024)

[0003] At present, there is no effective solution to the grating aperture limitation in the double grating spectral beam combining. SUMMARY

[0004] The purpose of the present application is to solve the problem of limited number of beams in the double grating spectral beam combining scheme in the spectral beam combining technology, and provide a spliced double grating spectral beam combining device and method.

[0005] The technical solution of the present application is as follows:

[0006] A spliced double grating spectral beam combining device, comprising: a spliced grating, a spliced grating clamp, an output grating, and an output grating clamp, wherein:

[0007] The spliced grating is composed of two or more sub-gratings spliced along the direction perpendicular to the grating lines, and the sub-gratings have the same line density, parallel grating lines and coplanar grating surfaces, and each sub-grating can be bonded or separated;

[0008] The spliced grating clamp is used to install the spliced grating, and can independently realize three-dimensional displacement adjustment of each sub-grating and rotation angle in three orthogonal directions;

[0009] The output grating has the same line density as the spliced grating, the grating lines are parallel to each other, and the grating surfaces are parallel to each other;

[0010] The output grating is installed on the grating clamp, and the output grating is parallel to the surface of the spliced grating and the grating lines are parallel through adjustment of the grating clamp.

[0011] The grating clamp is used to install the output grating, and can adjust the three-dimensional displacement of the output grating and the rotation angle in three orthogonal directions;

[0012] Preferably, the spliced grating and the output grating are preferably reflective plane gratings.

[0013] Further, the sub-gratings in the spliced grating are fixed by optical glue or arranged separately by maintaining relative positions through a clamp.

[0014] Further, the splicing grating and the output grating are both reflective plane diffraction gratings.

[0015] Further, the splicing grating clamp and the output grating clamp are respectively fixedly connected with the optical platform or the support through a mechanical connection mode.

[0016] A splicing double-grating spectrum synthesis method using the above device, characterized in that the method comprises the following steps:

[0017] arranging the sub-beam array output by the plurality of lasers of different wavelengths λ i into a parallel beam array, and making the parallel beam array enter the surface of the splicing grating at the same incident angle θ;

[0018] adjusting the output grating clamp to make the output grating parallel to the surface of the splicing grating and the grating lines aligned, and after the secondary diffraction of the output grating, the directions of the outgoing beams of all wavelengths are consistent, and the beams are synthesized into one laser beam.

[0019] Preferably, the sub-beam array is located in the same horizontal plane, and all the sub-beams are parallel to each other.

[0020] The method requires that the sub-grating array and the grating satisfy the following conditions:

[0021] ,

[0022] wherein λ i is the wavelength of the i-th beam in the sub-beam array, λ i-1 is the wavelength of the i-1-th beam in the sub-beam array, θ is the incident angle of all the sub-beams to the splicing grating, θ i is the diffraction angle of the i-th beam on the splicing grating, θ i-1 is the diffraction angle of the i-1-th beam on the splicing grating, Λ is the line density of the splicing grating and the output grating, m is the diffraction order of the splicing grating and the output grating, D is the array spacing of the i-th beam and the i-1-th beam, and L is the vertical spacing of the surfaces of the splicing grating and the output grating.

[0023] The number of the spectrum synthesis beams is increased and the output power is improved by increasing the number of the sub-gratings in the splicing grating to expand the incident grating aperture.

[0024] The technical effects of the present application are as follows:

[0025] 1) The device of the present application combines and splices a plurality of gratings along the vertical grating line direction to expand the grating incident aperture, thereby increasing the number of spectrum synthesis beams and greatly improving the upper limit of the spectrum synthesis output power.

[0026] 2) Based on the spectrum synthesis method of the application, the second grating is used for dispersion compensation, the output power is improved while the good beam quality is maintained, the spectrum synthesis of any wavelength can be realized by adjusting the sub-beam spacing and the double grating spacing, it has more flexible applicability and easy to realize characteristics, and has important application reference value in the field of high power laser technology. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Figure is a schematic diagram of the spliced double grating spectrum synthesis device of the application;

[0028] Figure 2 Figure is the optical path diagram of the four light beams spectrum synthesis realized by the spliced grating in Example 1;

[0029] Figure 3 Figure is the test spectrum of the output light beam after the four light beams spectrum synthesis realized by the spliced grating in Example 1.

[0030] In the figure: 1-spliced grating, 2-spliced grating clamp, 3-output grating, 4-output grating clamp, L is the vertical distance between the spliced grating and the output grating, D is the vertical spacing between the incident light beams, λ i is the wavelength of different incident light beams, N is the total number of incident light array sub-beams, θ is the incident angle of the incident light on the spliced grating, X, Y and Z are three mutually orthogonal directions, wherein the XY plane is parallel to the horizontal plane, the grating lines of the spliced grating and the output grating are parallel to the Z direction, and the incident light beam array is located in the same horizontal plane; 5-first laser, 6-second laser, 7-third laser, 8-fourth laser. DETAILED DESCRIPTION

[0031] The application will be further described below in conjunction with examples and drawings, but the protection scope of the application should not be limited thereby.

[0032] Reference Figure 1 As shown in the figure, the spliced double grating spectrum synthesis device of the embodiment includes a spliced grating 1, a spliced grating clamp 2, an output grating 3 and an output grating clamp 4. The spliced grating 1 is spliced by two 50mm×50mm reflective plane sub-gratings, the line density of each sub-grating is 400 lines / mm, and the TM polarization high diffraction efficiency is-1 order diffraction. The sub-grating is installed on the optical platform through the spliced grating clamp 2, the clamp has six degrees of freedom adjustment capability, can independently adjust the linear displacement (accuracy ±5μm) and rotation angle (accuracy ±10 arc seconds) of each sub-grating along the X, Y and Z axes.

[0033] The output grating 3 adopts a 50mm*50mm reflective plane grating with the same specification as the spliced grating, and is installed through an output grating clamp 4, which also has a six-degree-of-freedom adjustment function. During installation, first, the surface coplanarity error of the two sub-gratings of the spliced grating 1 is less than λ / 10 (λ=632.8nm) and the grating line parallelism error is less than 5 arcseconds by measuring and adjusting through a laser interferometer; then the surface parallelism error of the output grating 3 and the surface of the spliced grating 1 is less than λ / 10 and the grating line parallelism error is less than 5 arcseconds by adjusting the output grating clamp 4.

[0034] As shown in Figure 2 The spliced dual-grating spectrum synthesis device according to the present application builds a dual-grating spectrum synthesis light path, wherein the spliced grating 1 is composed of two identical sub-gratings spliced along the direction perpendicular to the grating lines, the sub-grating is a 50mm*50mm aperture reflective plane grating with a line density of 400 lines / mm and a TM polarization high diffraction efficiency at level-1. The two sub-gratings are spliced through a spliced grating clamp 2 and the surfaces of the two sub-gratings are parallel. The output grating 3 has the same size and line density as the spliced grating, and is adjusted to be parallel to the spliced grating through an output grating clamp 4. The incident light array is composed of four lasers, i.e. a first laser 5, a second laser 6, a third laser 7 and a fourth laser 8, with wavelengths of 3160nm, 3350nm, 3500nm and 3750nm respectively. According to the spectrum synthesis method of the present application, the first laser and the second laser beam interval is 15mm, the second laser and the third laser beam interval is 11mm, and the third laser and the fourth laser beam interval is 30mm, which are calculated by formula (I). The vertical plane distance between the spliced grating and the output grating is 126mm. The four light beams are incident on the spliced grating at an angle of 48°, converge to the same point on the output grating after diffraction, and are combined into a light beam after secondary diffraction. The spectrum of the synthesized light beam is shown in Figure 3 As shown in

[0035] Compared with the traditional single large-size grating scheme, the present embodiment adopts two standard-size 50mm*50mm sub-gratings for splicing, realizes the function of a 100mm*50mm large-aperture grating, breaks through the manufacturing limit of a single large-size grating, expands the aperture of the first grating by one time, simultaneously increases the synthesis number from the conventional 2 to 4, and correspondingly increases the output power by one time.

Claims

1. A tiled dual-grating spectral synthesis device, comprising: The application relates to a parallel light beam array synthesis device and method. The application comprises the following parts: A spliced grating (1) is composed of at least two independently processed sub-gratings in the direction perpendicular to the grating lines, the line density of each sub-grating is the same, the grating lines are parallel to each other, and the grating surfaces are arranged in the same plane; A spliced grating clamp (2) is connected with the spliced grating (1) and is used for fixing and adjusting the spatial position of each sub-grating, can independently realize the linear displacement of each sub-grating in X, Y and Z directions and the rotation angle adjustment around the X, Y and Z axes; An output grating (3) is arranged downstream of the diffraction light path of the spliced grating (1) and is arranged in parallel with the spliced grating in the same line density, the grating lines are parallel, and the grating surface is parallel to the spliced grating surface; An output grating clamp (4) is connected with the output grating (3) and is used for fixing and adjusting the spatial position of the output grating, can realize the linear displacement of the output grating in X, Y and Z directions and the rotation angle adjustment around the X, Y and Z axes; Wherein, X, Y and Z constitute a space rectangular coordinate system, the Y axis is perpendicular to the surface of the spliced grating (1) and the output grating (3) and points to the grating normal direction, the X axis is perpendicular to the grating line direction and points to the grating dispersion direction, and the Z axis is parallel to the grating line direction; ， wherein λ i is the wavelength of the i-th beam of the array of sub-beams, λ i-1 is the wavelength of the i-1-th beam of the array of sub-beams, θ is the angle of incidence of all the sub-beams on the tiling grating (1), θ i is the diffraction angle of the i-th beam on the tiling grating (1), θ i-1 is the diffraction angle of the i-1-th beam on the tiling grating (1), Λ is the linear density of the tiling grating (1) and of the output grating (3), m is the diffraction order of the tiling grating (1) and of the output grating (3), D is the array pitch of the i-th beam and of the i-1-th beam, L is the perpendicular distance between the surfaces of the tiling grating (1) and of the output grating (3).

2. The tiled two-grating spectral synthesizer of claim 1, wherein, The parameters of the sub-grating array and the grating satisfy the following conditions:

3. The tiled two-grating spectral synthesizer of claim 1, wherein, The sub-gratings in the spliced grating (1) are fixed by optical glue or are separately arranged by the clamp.

4. The tiled two-grating spectral synthesizer of claim 1, wherein, The spliced grating (1) and the output grating (3) are both reflective plane diffraction gratings.

5. A tiled dual-grating spectral synthesis method using the apparatus of any of claims 1-4, characterized in that, The spliced grating clamp (2) and the output grating clamp (4) are respectively fixedly connected with an optical platform or a support through a mechanical connection mode. The sub-beam array of laser outputs of multiple different wavelengths λ i is arranged into a parallel beam array, and is incident to the surface of the tiling grating (1) at the same incident angle θ; The application comprises the following steps:

6. The tiled double-grating spectral synthesis method of claim 5, wherein, The output grating (3) is parallel to the surface of the spliced grating (1) and the grating lines are aligned by adjusting the output grating clamp (4), after the secondary diffraction of the output grating (3), the directions of all the wavelength exit light beams are consistent and are combined into a laser beam.

7. The tiled two-grating spectral synthesis method of claim 5, wherein, Each sub-beam in the parallel light beam array is parallel to each other and is located in the same plane parallel to the surface of the spliced grating (1).

8. The tiled two-grating spectral synthesis method of claim 5, wherein, The spliced grating (1) and the output grating (3) are arranged in parallel, and the vertical distance between the grating surfaces is L. The number of the sub-gratings in the spliced grating (1) is increased to expand the grating aperture of the incident light, thereby increasing the number of the spectrum synthesis light beams and improving the output power.

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