220 nm deep-UV coherent source based on fifth-harmonic generation in ADP and DKDP crystals

Based on the 1.1 mu m laser radiation obtained by parametrically amplifying Yb:YAG laser using frequency doubling of Nd:YAG laser, a 220 nm deep-UV coherent source was systematically presented via the efficient fifth-harmonic generation (FiHG) in NH4H2PO4 (ADP) and KD2PO4 (DKDP) crystals. In ADP crystals, noncritical phase-matching (NCPM) fourth-harmonic generation (FHG) and FiHG were realized at 109.4 and 31.6 ?, respectively. For DKDP crystals, we demonstrated the critical phase-matching FHG at 57.5 ? and verified that NCPM FiHG can be achieved at 38.7 ?, which was the first demonstration of the FiHG using the DKDP crystal to our knowledge. The energy-dependent conversion efficiencies, angular acceptances, and temperature acceptances of these nonlinear processes were systematically measured. The highest total conversion efficiencies from 1.1 mu m to the fifth harmonic in ADP and DKDP crystals were 17.5% and 23.6%, respectively. Owing to the large-aperture availability of KDP-family crystals, this work paves the way for the generation and application of high-energy and high-peak-power deep-UV laser radiation. (C) 2022 Author(s).