Manufacturing of optical elements by non-contact laser processing

Abstract

We report on a photonic process chain to manufacture optical elements by non-contact all laser based micro-processing. Firstly, pre-defined optics geometries are generated by high-precision 1030 nm femtosecond layer-by-layer ablation. In order to meet high surface quality requirements, inevitable stipulated for optical use, the surface of thus generated elements has to be smoothened by subsequent 10.6 μm CO2 laser polishing. To demonstrate this surface finishing process, a complex optic geometry i.e. an axicon array consisting of 37 individual axicons is fabricated within 23 minutes while the polishing shows a reduction of the surface roughness from 0.36 μm to 48 nm. The functionality of the fabricated optic is tested using the 1030 nm wavelength ultrashort pulsed laser. Several sub-Bessel beams exhibiting the typical zeroth-order Bessel beam intensity distribution are observed, in turn confirming the applied manufacturing process to be well applicable for the fabrication of complex optic geometries. Cross sections of the quasi-Bessel beam at the axicon in the middle of the array in both, x- and y-direction, show an almost identical intensity profile, indicating the high contour accuracy of the axicon. Detailed investigations of the axicon in the middle of the array show a tip rounding of 1.37 mm while the sub-beam behind this axicon is measured to have a diameter of 9.5 μm (FWHM) and a Bessel range in propagation direction of 8.0 mm (FWHM).