Comprehensive numerical design approach for refractive laser beam shapers to generate annular irradiance profiles

Abstract. A refractive laser beam shaper typically consists of either two plano-aspheric lenses or one thick lens with two aspherical surfaces. Ray mapping is a general optical design technique for irradiance reshaping based on geometric optics. Although ray mapping, in principle, allows generating any rotational-symmetric irradiance profile, in the literature this technique is mainly used to transform a Gaussian irradiance profile to a uniform rotational-symmetric profile. For more complex profiles, especially with low intensity in the inner region (such as annular profiles), a high sampling rate is required to ensure an accurate calculation of the surfaces. In practice, the high sampling rate increases the numerical effort to calculate the aspherical surfaces and the simulation time to verify the design considerably. In this work, we evaluate different sampling approaches and surface construction methods. This allows us to propose and demonstrate a comprehensive numerical approach to efficiently design refractive laser beam shapers to generate rotational-symmetric collimated beams with annular irradiance profiles. Ray tracing analysis for several annular irradiance profiles demonstrates the excellent performance of the designed lenses and the versatility of our design procedure.