Vacuum ultraviolet second-harmonic generation in NH<sub>4</sub>B<sub>4</sub>O<sub>6</sub>F crystal.
basic_science · Level V
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- Record sourced from PubMed, PMID 41606317.
- Also identified by DOI 10.1038/s41586-025-10007-z.
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Abstract
Vacuum ultraviolet (VUV, 100-200 nm) light sources are crucial for advanced spectroscopy, quantum research and semiconductor lithography<sup>1-3</sup>. Compared with conventional large-scale VUV generation technologies<sup>4-7</sup>, second-harmonic generation (SHG) through nonlinear optical (NLO) crystals<sup>8-10</sup> is the simplest and most efficient method. However, the scarcity of suitable NLO crystals has constrained the production of VUV light through SHG: existing materials fail to meet phase-matching requirements, suffer from low conversion efficiency or have severe growth limitations<sup>11-19</sup>. In this study, we report the development of the fluorooxoborate crystal NH<sub>4</sub>B<sub>4</sub>O<sub>6</sub>F (abbreviated as ABF) as a promising material for VUV light generation. 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 provides further material in the NLO field, with potential for applications in compact, high-power VUV lasers using ABF.