Temperature Characteristics of a Dielectric Multilayer Mirror (PbF₂-MgF₂) for Near UV

Abstract

A dielectric multilayer mirror, which was composed of 25 layers of PbF₂ and MgF₂ and whose center wavelength was 395 nm, was heated up to 370°C in air. Transmittance characteristics were observed while the mirror was kept at elevated temperatures. The characteristics were unchanged from room temperature to 170°C. The mirror heated up to 370°C had high absorption. These phenomena were found to correspond with the change of structures of lead fluoride film with the aid of X-ray diffraction patterns.