Advances in the generation of coherent lasers at wavelengths below 200 nm as well as the associated equipment and technologies have greatly spurred the development of nonlinear optical (NLO) materials that are capable of phase-matching in the deep-ultraviolet (deep-UV) spectral regions. However, few crystals can meet the technical demands, and studies to date have focused mainly on finding the next competitive candidates. Consequently, several crystals have emerged that hold great potential for the production of deep-UV harmonic coherent light, which benefit from newly developed systems with novel NLO-active units and chromophores. This Review provides a comprehensive overview of the developments of emergent candidates in the field of deep-UV NLO materials, discussing the recent efforts and active advances in the search for superior systems and in understanding their structure-property relationships. The intention is to provide a clear perspective on the current emergent deep-UV NLO candidates, and to accelerate the discovery of next candidates with high performances to meet the urgent demands.
Keywords: borates; deep-ultraviolet; fluorooxoborates; nonlinear optical materials; second harmonic generation.
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.