Deep-UV laser source based on χ (2) optical frequency conversion and χ (3) stimulated Raman scattering

By integrating χ (2) optical frequency conversion and χ (3) stimulated Raman scattering (SRS) technology, we demonstrated a new, to the best of our knowledge, deep-UV laser generation scheme near 200 nm in a non-cryogenic KD 2 PO 4 (DKDP) crystal. Based on an Nd:YAG laser (1064 nm, ω 1 ) and cascaded LiB 3 O 5 and DKDP crystals, a 266 nm radiation was obtained firstly by the second- and fourth-harmonic generation (SHG and FHG) ( ω 4 ). The energy conversion efficiency from ω 1 to ω 4 was 24.8%. Meanwhile, the Stokes lights ( ω R ) were stimulated by the Nd:YAG laser in a KGd(WO 4 ) 2 crystal with two polarization-dependent Raman shifts of 768 cm −1 and 901 cm −1 . Finally, 3.5 mJ, 216.3 nm, and 3.1 mJ, 217 nm deep-UV laser sources were obtained in a DKDP crystal by the sum-frequency generation (SFG) of ω R and ω 4 . The total conversion efficiency from 1064 nm infrared to ∼200 nm deep UV was ∼3%. This scheme, by systematically combining the χ (2) and χ (3) nonlinear effects, overcame the phase-matching limitation of traditional schemes to acquire high-energy 200 nm wave band deep UV via the fifth-harmonic generation (FiHG) in the DKDP crystal, which may provide a new way for the deep-UV laser generation with high energy and high-peak power.