Abstract
For a high-power slab solid-state laser, obtaining high output power and high output beam quality are the most important indicators. Adaptive optics systems can significantly improve beam qualities by compensating for the phase distortions of the laser beams. In this paper, we developed an improved algorithm called Adaptive Gradient Estimation Stochastic Parallel Gradient Descent (AGESPGD) algorithm for beam cleanup of a solid-state laser. A second-order gradient of the search point was introduced to modify the gradient estimation, and it was introduced with the adaptive gain coefficient method into the classical Stochastic Parallel Gradient Descent (SPGD) algorithm. The improved algorithm accelerates the search for convergence and prevents it from falling into a local extremum. Simulation and experimental results show that this method reduces the number of iterations by 40%, and the algorithm stability is also improved compared with the original SPGD method.
Highlights
High-power solid-state lasers have been widely used in many fields such as machinery, medical, and defense [1,2,3,4,5,6]
The thermal effect of the laser introduces wavefront distortion, which leads to degradation of beam quality [7,8,9]
The adaptive optics technology measures the wavefront distortion through the wavefront sensor and uses the control system to control the deformable mirror to correct the wavefront distortion, which can effectively improve the laser beam quality [15,17]
Summary
High-power solid-state lasers have been widely used in many fields such as machinery, medical, and defense [1,2,3,4,5,6]. With the development of lasers, applications such asspacebased laser space debris cleanup have put forward new requirements for laser systems These scenarios require the laser system to have a high average output power and high output beam quality and require the system to be simple, compact, and miniaturized. The merit function usually selects a certain evaluation index of beam quality, such as sharpness function, Strehl ratio (SR), power in the bucket (PIB), etc. This method does not require a complex wavefront sensor system to measure wavefront distortion. The laser beam cleanup could be achieved by searching for the best voltage matrix of DM to optimize the merit function, as shown in Equation (2)
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