Fabrication of high-quality cavity mirror

The surface of K9 glass substrate whose size is 220x220x40mm3 is polished by bowl-feed polish with polishing agent of ultra pure water combined with cerium dioxide (CeO2). The super smooth surface with standard rms surface roughness less than 1 nm and reflective wavefront 0.127 λ(p-v) (λ=632.8 nm) was got. The high reflective thin film, whose reflectivity measured by Lambda 19 photometer is more than 99.5% at wavelength 1054 nm for incidence angle 0°, and whose laser induced damage threshold is 26 J/cm2 (1054 nm, 1 ns), was coated on this super smooth surface of K9 glass substrate by electronic beam evaporation deposition in the APS1504 coating machine. After alternately coating hafnia (HfO2) and silicon dioxide (SiO2) multilayer on the K9 glass substrate surface, this mirror's reflective wavefront is 0.17 λ(p-v) (λ=632.8 nm). The high quality cavity mirror was got.