Vacuum ultraviolet second-harmonic generation in NH4B4O6F crystal

Vacuum ultraviolet (VUV) nonlinear optical (NLO) crystals are essential for generating compact, high-power VUV laser sources via second-harmonic generation (SHG). However, the development of such sources has been impeded by the lack of suitable NLO crystals. In this study, we report the development of the fluorooxoborate crystal NH₄B₄O₆F (ABF) as a promising material for VUV light generation. For the first time, VUV devices with specific phase-matching angles were constructed, achieving a record 158.9 nm light through phase-matching SHG and a maximum nanosecond pulse energy of 4.8 mJ at 177.3 nm with a conversion efficiency of 5.9 %. The enhanced NLO performance is attributed to optimized arrangements of fluorine-based units creating asymmetric sublattices. This work represents a significant milestone in the field of NLO materials, paving the way for the future applications of compact, high-power VUV lasers utilizing ABF.