199 nm vacuum-ultraviolet second harmonic generation from SrB4O7 vertical microcavity pumped with picosecond laser

Abstract

We have proposed highly efficient microcavity wavelength conversion devices that do not utilize the birefringence or ferroelectricity of crystals. In this study, we utilized a low-birefringence paraelectric SrB₄O₇ crystal with significant potential for wavelength conversion and high transparency down to 130 nm and succeeded in achieving 199 nm vacuum-ultraviolet second harmonic generation (SHG) with a picosecond laser. The wavelength of 199 nm is shorter than the theoretical minimum for SHG in BaB₂O₄ of 205 nm. Our device could be a practical vacuum-ultraviolet SHG device, enabling significantly smaller and more efficient vacuum-ultraviolet laser sources compared to conventional systems.