A review on structure-performance relationship toward the optimal design of infrared nonlinear optical materials with balanced performances

Abstract

Infrared (IR) lasers have been widely applied in the many military and civil fields. Nonlinear optical (NLO) crystals have been developed as the critical materials to achieve the efficient IR laser output by the typical frequency-conversion technology. However, commercial IR NLO materials are seriously limited in the IR region because of their low laser-damage thresholds (LDTs) or harmful two-photon absorption (TPA). Therefore, the discovery of new IR NLO materials with optimal key performances (concurrently large NLO coefficient (dij) and wide optical bandgap (Eg)) has become imperative. Recently, metal chalcogenides have become a rich source for exploration of IR NLO materials and hundreds of them have been discovered. Based on the good balance between experimental Eg (≥3.0 eV) and dij (≥0.5 × AgGaS2) required for one IR NLO material, to our best knowledge, about 49 chalcogenides satisfy the above condition while limiting the scope to the equal or greater than ternary system. We focus on the structure-performance relationship for 49 compounds and the result shows that alkali or/and alkaline earth metals must be the preferred cations to maintain the wide Eg. Besides, their critical anionic groups are summarized and shown as follows: (i) typical tetrahedral MIIIQ4 (MIII = Ga, In) or/and MIVQ4 (MIV = Si, Ge; Q = S, Se) or PS4 units; (ii) d10 elements-centered (MIIQ4: MII = Zn, Cd) and typical MIIIQ4 or MIVQ4 tetrahedra; (iii) halogen-centered polyhedral ligands. So the combination of above anionic groups and alkali or/and alkaline earth metals into crystal structures produces the feasible design strategy to explore new IR NLO materials with excellent performances.