UV-Induced Nonlinear Absorption in Lanthanum Calcium Borate Single Crystals

It has been revealed that lanthanum calcium borate (La2CaB10O19) crystals show two-photon absorption (TPA) induced by a UV laser field. UV-induced TPA measurements were performed in the spectral range of 475−1130 nm using as fundamental beam the third harmonics of the 28 ps Nd−YAG pulsed laser as a pumping beam for LiB3O5 optical parametrized generator using Z-scan method. Investigations performed by the Z-scan method were done during illumination by a Xe−F laser (λ = 217 nm) as a photoinducing (pumping) beam. The pumping laser beam created a thin surface layer (about 80−90 nm) that was the source of the observed photoinduced TPA. The highest values of the TPA β coefficients were achieved for polarization of the pumping light directed along the second-order crystallographic axis of the investigated crystals. The obtained values of the TPA coefficients were higher than those for the BiB3O6 crystals investigated earlier by us.