Ion beam sputtering for plane and curved optics on 2-meter scale

Abstract

Optical coatings are essential for many applications of excimer or solid state lasers in industry and science. An increasing demand for larger optics of highest quality, mainly generated by the display industry processing active matrix organic light emitting diode (AMOLED) backplanes, is posing new challenges for substrate and coating suppliers. For the deposition process development principally the coating uniformity, but also the handling and the cleaning steps of optics with one edge length (L) above 1 meter and several kilograms of weight have to be considered. To provide coatings for optics up to 2 meter edge length, a new ion beam sputtering (IBS) machine was developed and built at LASEROPTIK. This contribution describes an approach to adapt the IBS technology with its advanced coating quality for small optics (L≤50mm) to the field of large area deposition (L≥1m). Applying a customized linear drive, the MAXIMA deposition machine is able to coat optics of up to 100kg weight sequentially. Experimental results on the uniformity, the spectral characteristics and the laser damage resistance of dielectric single- and multilayer coatings are presented and compared with the performance of standard IBS thin films. Furthermore, the deposition of thin films on convex curved surfaces applying curvature dependent movement profiles is discussed. Finally the run to run stability is evaluated on the basis of concrete coating examples.