Li2HgMS4 (M = Si, Ge, Sn): New Quaternary Diamond-Like Semiconductors for Infrared Laser Frequency Conversion

Kui Wu,Shilie Pan

doi:10.3390/cryst7040107

Abstract

A new family of quaternary diamond-like semiconductors (DLSs), Li2HgMS4 (M = Si, Ge, Sn), were successfully discovered for the first time. All of them are isostructural and crystallize in the polar space group (Pmn21). Seen from their structures, they exhibit a three-dimensional (3D) framework structure that is composed of countless 2D honeycomb layers stacked along the c axis. An interesting feature, specifically, that the LiS4 tetrahedra connect with each other to build a 2D layer in the ac plane, is also observed. Experimental investigations show that their nonlinear optical responses are about 0.8 for Li2HgSiS4, 3.0 for Li2HgGeS4, and 4.0 for Li2HgSnS4 times that of benchmark AgGaS2 at the 55–88 μm particle size, respectively. In addition, Li2HgSiS4 and Li2HgGeS4 also have great laser-damage thresholds that are about 3.0 and 2.3 times that of powdered AgGaS2, respectively. The above results indicate that title compounds can be expected as promising IR NLO candidates.

Highlights

Solid-state lasers have shown a wide range of applications in the fields of military, industry, medical treatment and information communications [1,2]
In order to ensure the reasonability of crystal structures of title compounds, the bond valence [85,86] and the global instability index (GII) [87,88,89] were systemically studied (Table 1)
GII can be derived from the bond valence concepts, which represent the tension of lattice parameters and are always used to evaluate the rationality of structure

Summary

Introduction

Solid-state lasers have shown a wide range of applications in the fields of military, industry, medical treatment and information communications [1,2]. To extend the laser wavelength ranges, frequency-conversion technology on nonlinear optical (NLO) materials was invented and has been further developed for decades [5]. For the IR region, outstanding IR NLO materials were rarely discovered and only several ternary diamond-like semiconductors (DLSs), such as AgGaS2 , AgGaSe2 and ZnGeP2 , have been commercially used [35,36,37]. They have high second harmonic generation (SHG) coefficients and wide IR transmission regions, some of the self-defects including the low laser-damage thresholds (LDTs) or strong two-photon absorption (TPA) still seriously hinder their practical application. Many reports indicate that cations with second order Jahn–Teller distortions, lone electron pairs or d10 configuration can contribute to good SHG response with the cooperative effects of typical tetrahedral

Methods

Results

Conclusion