LiNaB4O7 Crystals as a Material for Optically Induced Elastoopticity

During bicolor optical treatment by Nd:YAG laser radiation (λ = 1060 nm) and its coherent second harmonic (λ = 530 nm) of the LiNaB 4 O 7 (LNTB) crystals (space group Fdd 2), a substantial increase in the elastooptic coefficient at λ = 633 nm (up to 9 × 10 -13 m 2 /N) was revealed. The corresponding effect was maximal for the diagonal piezooptic PO xxxx tensor component, where x is directed along the second-order crystallographic axes. The effect appears at temperatures below 80 K and achieves its maximal value at T = 4.2 K. The phenomenon appears after 2 min of optical treatment under laser power densities above 0.6 GW/cm 2 and is saturated after 5 min of the bicolor optical coherent treatment. The elastooptical effect decreases at least one order at temperatures below 50 K and 6 min after switching off the bicolor laser treatment.