Dependence of refractive indices on deuterium content in K(H1−xDx)2PO4 crystals

In this work, refractive indices of K(H1−xDx)2PO4 crystals, in which the range of x was from 0 to 1, were measured in the visible region by V-prism method. The measured data revealed that both refractive index and birefringence decreased with the increasing of the deuterium content in K(H1−xDx)2PO4 crystals. Furthermore, there is a good linear dependence of refractive index on deuteration level. In terms of numerical fits to Sellmeier formula were made, permitting the interpolation consistent with the experimental data. Refractive indices of deuterated KDP crystal with arbitrary deuterium content at varying wavelength are provided to predict phase-matching behavior of frequency doubling according to our data and formulas. Meanwhile, our results provide a potential method to quantify the deuterium content of K(H1−xDx)2PO4 crystals by measuring the refractive index.

► We measured the refractive indices of K(H1−xDx)2PO4 crystals with different deuterium content at various wavelength.
► The dependence of refractive index on deuterium content is analyzed.
► The introduction of D, lowered the magnitude of both no and ne.
► meanwhile, its good linear dependence is considered to be used in estimating deuterium content of crystal.
► Then a method is provided to predict refractive index of deuterated KDP with varying deuterium content at arbitrary wavelength.