<title>Characteristics of ZnSe aspheric beam shaper for CO<formula><inf><roman>2</roman></inf></formula> laser</title>

Abstract

CO<SUB>2</SUB> laser material processing is now being used increasingly in the area of electronics, specifically, for drilling micro holes (min. (phi) 50 micrometers ) in printed circuit. This has become possible through the use of galvanometer mirrors and Aspheric ZnSe f-theta lenses. ZnSe is a good infrared material because of wide transmission. We have succeeded in producing aspheric lenses by using a Single Point Diamond Turning (SPDT) lathe. Distribution of laser beam intensity mainly based on Gaussian distribution is non- uniform. Therefore, the rise great demand for uniform intensity distribution in the fields of heat processing. To obtain higher uniformity, attempts have to be made to convert non-uniform Gaussian distribution into top-hat shaped uniform intensity distribution for smoothly bending laser beams. In this study we propose it is possible to allow the surfaces of a lens to perform more than one function (the center portion functions as a concave lens and the rim portion functions as a convex lens). The Aspheric ZnSe beam shaper consists of two aspheric lenses. First one converts Gaussian profile to uniform irradiation, Second one performs phase matching (compensation). We design this optical component with our special method based on the optical ray tracing. The most important optical property, wave front distortion were measured by infrared interferometer. And we also show the intensity distribution through after beam shaper with high power CO<SUB>2</SUB> laser (>100 W).