Beam shaping imaging system for laser microprocessing with scanning optics

Abstract

Laser beam shaping systems converting Gaussian to flattop or other irradiance profiles are used in various solar cell manufacturing laser technologies to enhance their performance. Scanning over whole working field with using popular 2- and 3-axis galvo mirror scanners is very often important part of microprocessing systems. Therefore, combining of beam shaping optics with scanning heads is an important technical task in field of solar cells manufacturing. As the beam shaping optics it is suggested to apply field mapping refractive beam shapers πShaper having some important features: low output divergence, high transmittance, extended depth of field, capability to work with TEM00 and multimode lasers, as result providing a freedom in building various optical systems. De-magnifying of flattop laser beam can be realized with using imaging technique; the imaging optical system to be composed from F-ʘ lens of scanning head and additional collimating system to be used right after a πShaper. One of the problems in this approach is implementation of compact design of the collimating part. As a solution it is suggested to apply a specially designed Beam Shaping Unit being based on π Shaper and locating between a laser and a scanning head; the functions of that combined system are: conversion from Gaussian to flattop laser beam irradiance profile, compact collimator design, alignment features, easy adaptation to a laser and a scanning head used in particular equipment. There will be considered design features of refractive beam shapers π Shaper and Beam Shaping Unit, examples of optical layouts to generate flattop laser spots, which sizes span from several tens of microns to millimetres. Examples of real implementations and results of material processing will be presented as well.