Chalcophosphates: A plentiful source of infrared nonlinear optical materials

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 x Q 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. The structure chemistry of chalcophosphates and typical chalcophosphate IR NLO materials with excellent optical properties were reviewed and outlined. • The structural chemistry of chalcophosphate were reviewed, and more than 40 distinguished NLO-active [P x Q y ] units were identified. • The structural design strategies for high performance chalcophosphate IR NLO materials were summarized. • The typical chalcophosphate IR NLO materials with excellent properties were outlined. • The forthcoming opportunities and challenges in the fascinating fields were discussed.