Li5Cs(SO4)3: a potential zero-order wave plate material with short deep-ultraviolet cutoff edge

Abstract

Zero-order wave plates play an important role in the polarization measurements and laser industry, wherein few materials can satisfy both the requirements of small birefringence and a deep-ultraviolet (DUV; λ < 200 nm) transparency range. In this study, a new sulfate Li₅Cs(SO₄)₃, crystallized in the centrosymmetric P2₁/c (no. 14), was obtained by the high temperature melt method. Its single crystal structure features a three-dimensional framework consisting of [SO4], [LiO4] and [LiO5] tetrahedra, and is a congruent-melting compound with a reversible phase transition. The transmission range of Li₅Cs(SO₄)₃ shows that the crystal has a UV cutoff edge below 180 nm, and the theoretical calculations reveal that it has a minimal birefringence of 0.0046 @ 1064 nm. The optical properties indicate that Li₅Cs(SO₄)₃ is a potential zero-order wave plate material.