Synthesis of chiral high-entropy sulfides for non-linear optical applications

Non-centrosymmetric semiconductors may exhibit non-linear optical (NLO) properties. For application-relevant materials, a careful balance of high second-harmonic generation (SHG) and high laser damage threshold (LDT) as well as phase-matchability are required. We have previously identified (A)2Cu2Ge2S14 (A = Y, La, Sm, and Gd) phases as promising NLO materials. Here, we developed a synthetic method to produce solid solution and high-entropy sulfides containing up to 9 elements. We report the synthesis, crystal structure, and NLO properties for solid solutions and high-entropy multi-metallic materials (HEMs) of the type (A)6(TM)xGe2S14 (A = La, Sm, Gd, mixture of (Y + La + Ce + Sm + Gd); TM = Mn, Cu; 1 <= x <= 2). In this work, we establish that nearly all phases are phase matchable and the HEA composition with Cu possesses a SHG signal enhancement of 1.5x as compared to the AgGaS2 (AGS) standard for the largest particle size, as well as a LDT value of 2.8x of AGS. Non-centrosymmetric semiconductors may exhibit non-linear optical (NLO) properties.

Automated summary

Non-centrosymmetric semiconductors exhibit important nonlinear optical properties. We developed a method to synthesize solid solutions and high-entropy sulfides, and studied their crystal structure and optical properties. The results show that most of these materials have good phase matchability, with the high-entropy alloy containing Cu showing higher SHG signal enhancement and LDT value.