Recent advances in ultraviolet and deep-ultraviolet second-order nonlinear optical crystals

Second-order nonlinear optical (NLO) crystals functioning in the ultraviolet (UV) and deep-ultraviolet (deep-UV) regions are critically important as frequency conversion materials for all-solid-state UV laser devices. In this review, we focus on recent studies of inorganic UV and deep-UV NLO crystals with wide UV transparency and SHG efficiency. Following an introduction describing crystal-design strategies for UV and deep-UV NLO materials, the manuscript is organized according to the type of inorganic anions (borates, carbonates, nitrates and phosphates). Special attention is given to the crystal structures, second-order NLO properties, and structure-property correlations. The concluding remarks highlight future prospects in the field, with emphasis on the superiority of the different types of UV and deep UV NLO crystals and the importance of large-size crystal growth for practical application in electrooptic devices. (C) 2018 Elsevier B.V. All rights reserved.