Breakthrough in High Quality LaBGeO ₅ Crystal for Deep Ultraviolet Quasi-Phase Matching Application

Deep ultraviolet (UV) lasers are essential for advanced laser technologies. Currently, only β-BaB 2 O 4 (β-BBO) and CsLiB 6 O 10 (CLBO) are used for nonlinear wavelength conversion in this range, but they face limitations like hygroscopicity and walk-off effects. Thus, alternative materials are needed for efficient frequency conversion. LaBGeO 5 crystals, a promising ferroelectric candidate for UV quasi-phase matching (QPM) devices, have been synthesized with well-developed facets. LBGO showcases remarkable properties: an absorption edge at 195 nm, second-harmonic generation intensity of 1.5 × KDP, and a laser-induced damage threshold of about 2.4 GW/cm 2 (@1064 nm, 10 ns, 10 Hz), with a transmittance of 78% at 266 nm. Its domain-switching ability arises from the distortion of [BO 4 ] tetrahedrons in [GeB 2 O 9 ] rings, marking a significant breakthrough in QPM crystal research and promising advancements in UV laser applications.