An overview of Mg-based IR nonlinear optical materials

Abstract

Infrared nonlinear optical (IR-NLO) materials play a vital role in generating IR laser output and have significant applications in the fields of communication, medicine, and security. At present, commercial IR-NLO crystals suffer from various performance drawbacks that constrain their range of applications. Therefore, the pursuit of designing and exploring new IR-NLO materials has emerged as an important avenue for the advancement of the IR laser industry. Benefiting from the various structural compositions, wide energy gaps, sufficient second-harmonic-generation intensities, strong laser-induced damage thresholds and favorable phase matching features, Mg-based IR-NLO materials have attracted wide attention in recent years. However, there has not been a specific review of this attractive family. In this overview, the recent advancements of Mg-based IR-NLO materials are summarized. These non-centrosymmetric compounds (including 36 chalcogenides and 4 pnictides) can be categorized into three types based on their chemical compositions: (i) ternary MgGa₂Se₄, MgSiP₂, MgSiAs₂, and Mg₃Si₆As₈; (ii) quaternary Li₄MgGe₂S₇, Li₂Mg₂M^III₂S₆ (M^III = Si, Ge), AEMg₆Ga₆S₁₆ (AE = Ca, Sr, Ba), RE₆MgSi₂S₁₄ (RE = Y, La–Nd, Sm, and Gd–Er), Li₂MgM^IVSe₄ (M^IV = Ge, Sn), Na₄MgM^III₂Se₆ (M^III = Si, Ge), Cu₂MgM^IVQ₄ (M^IV = Si, Ge; Q = S, Se), M^IMg₃M^III₃Q₈ (M^I = Na, Cu, Ag; M^III = Al, Ga; Q = S, Se), and Mg₂In₃Si₂P₇; and (iii) quinary Ba₆Cu_1.9Mg_1.1Ge₄S₁₆ and Ba₆Cu_1.94Mg_1.06Sn₄S₁₆. Their solid-state synthesis, crystal structures, optical properties and structure–activity relationships are systematically discussed. Finally, some useful conclusions and outlooks on this topic have been put forward.