Evaluation and prospect of Mid-Infrared nonlinear optical materials in f0 rare earth (RE = Sc, Y, La) chalcogenides

Mid-infrared (mid-IR) nonlinear optical (NLO) materials are extensively researched as a vital optoelectronic material family with widespread applications ranging from civil to military fields. Metal chalcogenides possess a wide range of IR transparency and vast structural diversity, making them ideal system for exploration of novel mid-IR NLO materials. Incorporating rare earth elements with 4f0 and 5f0 electrons, including Sc, Y, and La, into chalcogenide structures in mid-IR NLO materials has been actively studied in the recent years. In this review, we categorize all typical f0 rare earth (RE = Sc, Y, La) chalcogenides in the inorganic crystal structure database based on their NLO functional groups. We then assess their energy band gaps, NLO coefficients, birefringence, IR cut-offs, and mechanical properties using available experimental data and first-principles results and investigate the correlation between structural features and mid-IR NLO performance. It is showed that the f0 rare earth chalcogenides can possess suitable birefringence and NLO response for mid-IR NLO applications, while not compromising energy band gap, thus may have a well-balanced mid-IR NLO performance. The prospects of novel f0 rare earth chalcogenides with favorable mid-IR NLO performance are also discussed.