High surface laser-induced damage threshold of SrB₄O₇ single crystals under 266-nm (DUV) laser irradiation

Under 266-nm (deep ultraviolet, DUV) laser irradiation, an SrB₄O₇ (SBO) single crystal has been found to exhibit a surface laser-induced damage threshold (LIDT) of ∼ 16.4 J/cm², which is higher than those of a synthetic silica glass (4.8 J/cm²) and a calcium fluoride (CaF₂) crystal (11.4 J/cm²). By catalyst-referred etching (CARE), the LIDT of an SBO crystal can also be improved to around 24.1 J/cm², which is 1.4 and 6.0 times higher compared to an unetched crystal and a silica glass, respectively. With high surface LIDTs, SBO single crystals can then be used as optical window materials for high-power DUV laser systems.