Flattop beam generation and multibeam processing using aspheric and diffractive optics

Abstract

State-of-the-art optical techniques have been employed in the recent development of laser materials processing technology. One advanced application of aspheric optics is in homogenization, i.e., flattop beam generation, where an aspheric lens directly controls the wavefront of a laser beam and transforms its Gaussian intensity distribution into one with a circular flat top. Diffractive optics also function as a homogenizer, giving more flexibility in beam shapes, including square, rectangular, linear, or other complex shapes depending on the application. Those aspheric and diffractive homogenizers can be utilized for laser drilling, scribing, annealing, etc. Another important function of diffractive optics is in beam splitting for multibeam processing. A single laser beam is split into multiple beams that are converged onto multiple spot positions on a workpiece by a special lens having an f-sinΘ distortion characteristic. Since multibeam processing enables higher throughput with a simpler optical system than the conventional one, diffractive beam splitters are widely used for the laser processes in the mass production of electronic devices. In cases where a flattop multibeam is required, a homogenizer can be installed in the multibeam optical system. In this report, some examples of optical systems for practical applications are presented, with their design concepts and specifications.