High uniformity Bessel beam generated by the axicon with a high-order curved surface

Generating high uniformity Bessel beam is an interesting target in laser processing. An axicon with a high-order curved surface is proposed to generate Gaussian–Bessel beams with high uniformity and high energy utilization. The original phase function of the standard axicon is replaced by multiple polynomials, which are optimized by a combined algorithm employing the genetic algorithm and the unconstrained nonlinear minimization algorithm. Simulation and experiment results demonstrate that the combined algorithm not only significantly reduces the time complexity of the algorithm greatly but also achieves high uniform intensity distribution at the focal segment. By compensating and optimizing the fifth-order surface axicon, the energy utilization is 17.734%, and the uniformity can reach 93.86%. The processing experiment results confirmed that the presented method can extend the processing depth and obtain high quality.