Water-free fused silica for laser windows made by the reactive atmosphere process

Abstract

We have produced by the reactive atmosphere process (RAP) a new form of fused silica that is nearly free (of the order of 1 ppm) of water-derived impurities (OH−, H+). This RAP-fused silica is a vitreous form of the cristobalite crystal phase of SiO2 and not the quartz phase. Therefore, it is called “fused cristobalite”. This fused cristobalite exhibits simultaneously increased resistance to nuclear radiation, with no damage up to 10 Mrad (of 60Co gamma irradiation), and greatly increased IR transparency due to the lack of water absorption at the 2.73 μm OH stretch vibrational band. We present absorption measurements in the near-IR comparing our RAP-fused cristobalite with seven types of commercial fused sillica.