Refractive indices of KD2xH2(1–x)PO4 and RbD2xH2(1–x)PO4 crystals

The refractive indices of KD_2xH_2(1–x)PO₄ and RbD_2xH_2(1–x)PO₄ crystals decrease linearly with increasing x. Empirical dependences of the refractive indices for ordinary (n₀) and extraordinary (n_e) waves on the value of x are reported. It is shown that these dependences are related to an increase in the lattice parameters and reduction in the polarizability along the crystallographic X axis. The dependences obtained can be used in the design of frequency doublers and deflectors of laser radiation.