Performance simulation implementation system and method for lath laser with three-dimensional composite structure

Abstract

The invention discloses a three-dimensional composite structure slab laser performance simulation implementation system and method, and belongs to the technical field of solid lasers. The implementation method comprises the steps of obtaining a to-be-simulated target parameter; the target is used for calculating the pump light intensity and the laser light intensity of a specific position so as to calculate the output power of the pump light intensity and the laser light intensity; the pump light intensity, the laser light intensity, the pump light absorption coefficient and the laser gain coefficient of any point on the light beam transmission path are obtained to draw a light power result; and a thermal power result is obtained. The beneficial effects of the invention are that simulation results of related laser structures are provided for optimization and improvement of experimental parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lasers, and particularly relates to a system and method for simulating the performance of a three-dimensional composite structure slab laser. Background Art

[0002] Slab lasers have a high-power output capability that cannot be compared with other types of lasers. Structurally, a slab laser medium with a large cooling surface can more effectively reduce the thermal effect than a rod-shaped laser medium. Combining with a unique parallelepiped structure can achieve even-numbered reflections to completely symmetrically compensate for thermal aberration and achieve higher-quality laser output.

[0003] In the process of designing and fabricating high-power lasers, high-performance output is what we expect. However, the subsequent thermal effect has become an undeniable drawback. The resulting temperature rise, thermal stress, thermal lens, etc., further cause the beam quality to decline, limit the output power, and even damage the solid-state laser medium. Adopting a gradient doping structure can effectively improve the pumping uniformity of the laser medium, improve the thermal effect, and thus achieve higher power output.

[0004] A method for simulating the performance of a three-dimensional composite structure slab laser designed for this problem can be used to provide simulation results of the relevant laser structure for optimizing and improving experimental parameters. Summary of the Invention

[0005] The purpose of the present invention is to provide a system and method for simulating the performance of a three-dimensional composite structure slab laser.

[0006] According to one aspect of the present invention, there is provided a method for simulating the performance of a three-dimensional composite structure slab laser, the method comprising the following steps:

[0007] The laser structure simulated by the present invention is a double-end symmetric pumping structure, and its single-end pumping power and absorption coefficients at each level are to be set;

[0008] Based on the input single-end pumping power and absorption coefficients at each level, combined with the stimulated emission theory and the rate equation of Yb:YAG, the pump light intensity and laser light intensity at a specific position transmitted in the slab gain medium are simulated and calculated to calculate its output power.

[0009] Using the interpolation method, the pump light intensity and laser light intensity at any point on the beam transmission path, as well as the pump light absorption coefficient and laser gain coefficient, can be obtained to plot the optical power result.

[0010] Using the heat conduction equation combined with the finite element idea to obtain the thermal power result.

[0011] Furthermore, according to the stimulated emission theory, the rate equation of Yb:YAG can be obtained:

[0012]

[0013] wherein n1 and n2 are the particle number densities of the ground state and the excited state respectively, and τ f represents the fluorescence lifetime of the excited state, and I p and I l are the pump intensity and the laser intensity respectively, and I sp represents the pump saturation light intensity, and I sl represents the laser saturation light intensity.

[0014] Further, a double-end symmetric pumping structure is set, and combined with the image transfer efficiency of a specific 4f image transfer system and the reflectivity of a specific output mirror to calculate the optical power result.

[0015] Further, the pump light enters the slab, the gain medium absorbs the pump light, and the waste heat generated in the slab is the total power of the absorbed pump light minus the total power of the laser gain:

[0016] P p，total -P l，total =P heat

[0017] wherein, P p，total is the total power of the pump light absorbed in the slab, P l，total is the total power of the laser gain in the slab, and P heat is the total thermal power deposited in the slab.

[0018] Further, the finite element idea is introduced to calculate the distribution of the thermal power density.

[0019] Further, the simulation software is MATLAB simulation software.

[0020] Through the solution of the present invention, specific parameters of the target to be simulated are obtained, such as the pump power, etc. Based on the parameters, the output performance of the model is generated, such as the optical power result, etc.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] 1. Most of the existing systems for calculating the performance of lasers are for calculating single-concentration gradient media. And the theoretical basis for setting up their systems relies on the Lambert-Beer law, which has a large deviation from the actual situation. The present invention has improved the above two situations. The designed system can not only be used to calculate the case of single-concentration doping, but also the case of multi-concentration doping. The theoretical basis selects the more practical stimulated emission theory combined with the rate equation of Yb:YAG.

[0023] 2. Most of the existing methods for calculating the performance of lasers rely on ray tracing software such as TracePro to simulate the light field irradiance, and then cooperate with the heat source model to calculate the thermal field distribution. However, for lasers, part of the pump light energy is converted into heat, and the other part needs to be converted into the energy required for the laser. There is a deviation between only calculating the absorbed part of the pump light and the actual heat deposition. The conventional theoretical calculation method is based on the model of a double-ended single-pass pumped solid laser, assuming that the pump light is absorbed along the laser oscillation direction and solving it roughly according to the exponential decay law. Most of the above two calculation methods only consider the influence brought by the pump light during the calculation process, and do not consider the influence brought by the generated laser. In the present invention, starting from the stimulated emission theory and the rate equation of Yb:YAG, the influences brought by both the pump light and the laser are considered simultaneously. The pump light intensity and laser light intensity at a specific position transmitted in the slab gain medium are calculated to calculate its output power. The interpolation method can be used to obtain the pump light intensity and laser light intensity at any point on the beam transmission path, as well as the pump light absorption coefficient and the laser gain coefficient to plot the optical power result. Since the step size of our numerical simulation is very small, the pump and laser light intensities and absorption and gain coefficients obtained by interpolation will also be more in line with the theoretical values. The visualization of the calculation process is realized and the accuracy of the calculation result is improved. Subsequently, combined with the proposed internal heat source model, the thermal power density distribution is calculated, which is more in line with the actual situation.

[0024] The present invention simulates the performance of the three-dimensional composite structure slab laser using real physical parameters and existing physical theories, greatly improving the simulation authenticity and user experience.

[0025] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Show the flowchart of the simulation.

[0027] Figure 2 Show the initial interface of the software.

[0028] Figure 3 Show the schematic diagram of the output power obtained by simulation in the software.

[0029] Figure 4 Show the schematic diagram of the output power and optical power results obtained by simulation in the software.

[0030] Figure 5 Show the schematic diagram of the output power, optical power results and thermal power results obtained by simulation in the software. DETAILED DESCRIPTION OF THE INVENTION

[0031] To further understand the technical solution and beneficial effects of the present invention, the technical solution of the present invention and the beneficial effects produced thereby will be described in detail below with reference to the accompanying drawings.

[0032] The present invention provides a system for simulating the performance of a three-dimensional composite structure slab laser, which includes a parameter input component, a calculation output power component, a component for drawing the optical power result, a component for drawing the thermal power result, etc.

[0033] The parameter input component is used to input the absorption coefficient of the laser.

[0034] The calculation output power component is used to calculate the output power of the laser.

[0035] The component for drawing the optical power result is used to draw the pump light intensity and laser light intensity at any point on the beam transmission path, as well as the pump light absorption coefficient and laser gain coefficient.

[0036] The component for drawing the thermal power result is used to draw the thermal power density distribution by combining the internal heat source model and the finite element idea.

[0037] Further, the parameter input component is located in the "Settings" area on the left side of the page and includes four parameters to be input, namely: single-end pump power, central absorption coefficient, secondary absorption coefficient, and secondary-secondary absorption coefficient. The calculation output power component is in the output power area on the left side of the page, and clicking "Calculate" can display the output power result. The component for drawing the optical power result is located at the "Optical Power Result" position on the right side. The component for drawing the thermal power result is located at the "Thermal Power Result" position on the right side.

[0038] Based on the above system for simulating the performance of a three-dimensional composite structure slab laser, as Figure 1 shown, a method for simulating the performance of a three-dimensional composite structure slab laser is provided, which includes the following steps:

[0039] Step S1: Specify simulation parameters such as single-end pump power, central and secondary, and secondary-secondary absorption coefficients to determine the structure of the simulated laser for subsequent calculations;

[0040] Step S2: Calculate the pump light intensity and laser light intensity at a specific position transmitted in the slab gain medium based on the set simulation parameters to calculate its output power;

[0041] Further, considering that at a specific temperature, Yb:YAG has 2 F 7 / 2 the ground state and 2 F 5 / 2 the excited state two energy levels, and the transition occurs between the two sub-energy levels of 10327 cm -1 and 612 cm -1 ;

[0042] Based on the stimulated emission theory, the rate equations of Yb:YAG can be obtained:

[0043]

[0044] where n1 and n2 are the particle number densities of the ground state and the excited state respectively, and τ f represents the fluorescence lifetime of the excited state, I p and I l are the pump intensity and the laser intensity respectively, I sp represents the pump saturation light intensity, and I sl represents the laser saturation light intensity.

[0045] Meanwhile, set its boundary conditions:

[0046] I1(L)C = I2(L),

[0047] I2(0)D = I1(0),

[0048] I3(0) = I4(L) = I pump

[0049] 0 represents the position of the left end of the slab, L represents the position of the right end of the slab. C is the image transfer efficiency of the 4f image transfer system at the right end of the slab, D is the reflectivity of the output mirror, and I pump is the single-end pump light intensity.

[0050] Step S3: Use the interpolation method to obtain the pump light intensity, the laser light intensity, the pump light absorption coefficient, and the laser gain coefficient at any point on the beam transmission path to draw the optical power result;

[0051] Furthermore, in accordance with the calculation principle of the output power calculated above, combined with the interpolation method, visualize the calculated transmission situation to obtain the calculation image of the optical power result module.

[0052] Step S4: Calculate the waste heat generated in the slab and introduce the finite element idea to calculate the thermal power density distribution.

[0053] Furthermore, a part of the pump light energy is converted into heat, and another part needs to be converted into the energy required for the laser. There is a deviation between only calculating the absorbed part of the pump light and the actual heat deposition. At this time, a new internal heat source model is proposed as follows:

[0054] The pump light enters the slab, the gain medium absorbs the pump light, and the waste heat generated in the slab is the total power absorbed by the pump light minus the total power of the laser gain:

[0055] P p，total -P l，total = P heat

[0056] where, Pp，total is the total power of the pump light absorbed in the slab, P l，total is the total power of the laser gain in the slab, P heat is the total thermal power deposited in the slab.

[0057] Introduce the idea of finite element, divide the slab medium into a finite number of small elements, divide the gain region into small cubes, and calculate the thermal distribution of the entire gain region according to the absorption of the small cubes.

[0058] The present invention is described in detail by the following examples.

[0059] Configure the software and obtain the initial interface as Figure 2 shown. In step S1, set the single-end pump power to 30000W, the central absorption coefficient to 0.35 cm -1 , the secondary absorption coefficient to 0.27 cm -1 , the secondary-secondary absorption coefficient to 0.18 cm -1 .

[0060] In step S2, calculate the output power to be 34445.5W (as Figure 3 shown).

[0061] In step S3, use the interpolation method to obtain the pump light intensity, laser light intensity, pump light absorption coefficient, and laser gain coefficient at any point on the beam transmission path to obtain the optical power result (as Figure 4 shown).

[0062] In step S4, calculate the waste heat generated in the slab and introduce the finite element idea to obtain the thermal power density distribution (as Figure 5 shown).

[0063] The simulation results obtained through the above system and method for simulating the performance of the three-dimensional composite structure slab laser can be used to provide the simulation results of the relevant laser structure for the optimization and improvement of experimental parameters.

[0064] Although the operations of the method of the present invention are described in a specific order in the drawings, this does not require or imply that these operations must be performed in that specific order, or that all the shown operations must be performed to achieve the desired result. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, or one step may be decomposed into multiple steps for execution.

Claims

1. A system and method for simulating the performance of a three-dimensional composite structure slab laser, characterized in that: The method includes: The target gain medium geometric model is a parallelepiped structure with preset length, width, height and chamfer angles. Obtaining the single-end pump power and the absorption coefficients of each doped section as the structural parameters to be simulated; Setting the absorption coefficients of each section of the gain medium and using simulation software to solve for the output power under the geometric model; Based on the stimulated emission theory and the rate equations of Yb:YAG, the pump light intensity and laser light intensity at a specific position in the slab gain medium are simulated and calculated. Using the interpolation method, the pump light intensity and laser light intensity at any point on the beam transmission path, as well as the pump light absorption coefficient and laser gain coefficient, can be obtained to calculate the optical power result; Based on the heat conduction equation and the finite element idea, the thermal power result is obtained.

2. The system and method for simulating the performance of a three-dimensional composite structure slab laser according to claim 1, characterized in that, At a specific temperature, Yb:YAG has 2 F 7 / 2 the ground state and 2 F 5 / 2 two energy levels in the excited state, and the transition occurs between 10327 cm -1 and 612 cm -1 between the two sublevels. Using the theory of stimulated emission, the rate equation of Yb:YAG can be obtained: where n1 and n2 are the particle number densities of the ground state and the excited state respectively, and τ f represents the fluorescence lifetime of the excited state, I p and I l are the pump intensity and the laser intensity respectively, I sp represents the pump saturation intensity of light, and I sl represents the laser saturation intensity of light.

3. The system and method for simulating the performance of a three-dimensional composite structure slab laser according to claim 1, characterized in that, A double-end symmetric pumping structure is set, and combined with the image transfer efficiency of a specific 4f image transfer system and a specific output mirror reflectivity to calculate the optical power result.

4. The system and method for simulating the performance of a three-dimensional composite structure slab laser according to claim 1, characterized in that, The pump light enters the slab, the gain medium absorbs the pump light, and the waste heat generated in the slab is the total power of the absorbed pump light minus the total power of the laser gain, that is P p，total -P l，total =P heat Among them, P p，total is the total power of the pump light absorbed in the slab, P l，total is the total power of the laser gain in the slab, and P heat is the total thermal power deposited in the slab. The finite element idea is introduced to calculate the distribution of the thermal power density.

5. A system and method for simulating the performance of a three-dimensional composite structure slab laser, the method comprising visually simulating the output power, pump light intensity, laser light intensity, pump light absorption coefficient, laser gain coefficient, and thermal power density according to the geometric model and parameters.

6. A system and method for simulating the performance of a three-dimensional composite structure slab laser, characterized in that, The software development kit includes a simulation program, and the computer program, when executed by a processor, causes the processor to execute the simulation method according to any one of claims 1-4.

7. A system and method for simulating the performance of a three-dimensional composite structure slab laser, characterized in that, The simulation software is MATLAB simulation software.

8. A system and method for simulating the performance of a three-dimensional composite structure slab laser, characterized in that, The performance of the laser is determined according to the design scheme described in any one of claims 1-6.

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