Influence of gamma radiation on the second-order optical sceptibilities and piezoelectricity of the Rb1-xKxTiOPO4 single crystals

We have performed nonlinear optical and piezoelectric studies of the Rb1-xKxTiOPO4 (RKTP) (with x = 0.01 and 0.002) single crystals irradiated by ?-quanta at power 1.23 Gy. We have found that for non-irradiated samples with x = 0.01 the effective second-order susceptibilities determined from the powder-like micrometer samples were less than for x = 0.02 and the effective values of the second-order susceptibilities for 1064 nm were equal to 3.12 pm/V (x = 0.002) and 2.56 pm/V (x = 0.01). After the gamma irradiation the corresponding values were equal to 2.45 pm/V and 2.78 pm/V, respectively. Moreover, for the samples with x = 0.01 one can observe the occurrence of the damage at laser energy density equal to about several J/cm2. Such effect is absent for the pure KTP crystals and may be a consequence of substantial role of the intrinsic defects caused by insertion of potassium ions in the positions of the rubidium cations. At the same time the piezoelectrical constants show an opposite behavior with respect to the SHG.