Infrared optical properties of Li- and Xe-irradiated KTiOPO 4

Abstract

KTP was irradiated at 100 K and 295 K with Li ions and at 295 K with Xe ions. The infrared spectra of the Li-irradiated samples are consistent with a system consisting of a layer stack of undamaged KTP/amorphous KTP/undamaged substrate. Annealing of the samples leads to a growth of the covering layer at the expense of the amorphous layer. The damage yield of the sample irradiated at 100 K is noticeably higher, resulting in a greater thickness of the amorphous layer. The spectra show interference effects, indicating homogenous layer thicknesses. Such interference effects are absent for the Xe-irradiated samples. Spectral simulations revealed that there is no buried amorphous layer present in these samples. Instead, the latter samples consist of amorphous inclusions in undamaged crystalline KTP with a volume fraction depending on the energy dose. The spectra of the sample irradiated at an ion fluence of 3×1012 cm-2 are very similar to the spectrum of glassy KTP, indicating a strong structural relationship between ion-damaged amorphous KTP and glassy KTP. The dielectric function of amorphous KTP was determined and used, together with the principal dielectric functions of single-crystal KTP, to successfully simulate the spectra of a sample irradiated at an ion fluence of 2×1011 cm-2 by either the effective-medium approximation (EMA) or average-refractive-index theory (ARIT).