Recent advances in IR nonlinear optical chalcogenides with well-balanced comprehensive performance

Infrared nonlinear optical (IR-NLO) crystals have attracted many attentions due to the frequency-conversion capability to generate coherent tunable IR laser output for military and civil applications. Chalcogenides as a most popular branch of IR-NLO materials are the competitive candidates owing to their large second-harmonic generation (SHG) coefficient (deff) and broad transmission regions. Currently, how to obtain the non-centrosymmetric (NCS) structure and realize the coexistence of wide energy gap (Eg ≥ 3.0 eV), sufficient deff (≥ 1.0 × AgGaS2), and beneficial phase-matching (PM) feature are the two major challenges faced in this field. The former can be effectively solved through the combination of local asymmetric units and chemical substitution strategy, while for the latter, there is no systematic survey and lack of universally applicable methodology. In this review, 40 IR-NLO chalcogendides are selected based on the aforementioned two challenges and divided into 7 types according to the different chemical components. The composition-structure-performance relationships and the theoretical origin of their IR-NLO properties are summarized systematically. At length, some useful information and development prospects were briefly discussed, which may offer new ideas and promote the discovery of IR-NLO materials with the ideal comprehensive performance.