A deep-ultraviolet nonlinear-optical material with a wide bandgap and large static dielectric polarizability coefficient: Na6Si3F18

Abstract

A silicon-based noncentrosymmetric (NC) deep-ultraviolet (DUV) nonlinear optical material, Na₆Si₃F₁₈, has been synthesized through a hydrothermal method. Na₆Si₃F₁₈ possesses a [SiNa₉F₄₂] group, which is constructed by an isolated [SiF₆] octahedron and nine distorted [NaF₆] octahedra interconnected with one another to form a condensed 3D structure, which is beneficial to increase the static dielectric polarizability coefficient, which was calculated to be 4.3 times that of quartz. The first-principles calculations indicate that Na₆Si₃F₁₈ possesses a very large bandgap of 10.45 eV (∼118.76 nm), which originates from the [SiF₆] group and [NaF₆] group and is larger than that of SrB₄O₇. Na₆Si₃F₁₈ crystalizes in the P321 space group, and is a potential DUV nonlinear optical crystal with the addition of periodic phase match technology, which could break through the wall of 120 nm for all-solid-state lasers.