Chalcophosphates: A plentiful source of infrared nonlinear optical materials

Abstract

Developing high-performance nonlinear optical (NLO) crystals is an urgent need for advanced photoelectric technologies. However, the discovery of novel infrared (IR) NLO materials with desired properties is challenging. Chalcophosphate, combining the structural advantages of chalcogenide & phosphate, and showing a high probability (∼30 %, much higher than the one of ∼15 % in the inorganic compounds) to generate non-centrosymmetric crystal structures, was demonstrated as a promising system for searching new IR NLO crystals with excellent optical properties, and a great many NLO-active chalcophosphates were ‌reasonably designed and fabricated. To advance the targeted design of high-performance IR NLO crystals, this review provides a systematic and up-to-date summary on the abundant structural and chemical diversities of chalcophosphates, with a particular emphasis on the connection modes of distinguished [P_xQ_y] units; and the efficient progress on the structural design that achieved in the thiophosphate-, selenophosphate-, and mixed anionic-based chalcophosphate IR NLO candidates in recent years. Finally, the upcoming opportunities and challenges in the captivating fields were discussed.