Enhancing second harmonic generation response in infrared nonlinear optical material through Pb substitution: A study of Li2PbSiS4compound

Abstract

The demand for infrared nonlinear optical (IR-NLO) materials is increasing due to their applications in many civil and military fields. However, a critical challenge revolves around achieving a good balance between a large second harmonic generation (SHG) response and a high laser damage threshold (LDT). Based on earlier study on Li2SrSiS4 compound which showed good SHG and high LDT performances, and to afford one new NLO material, we propose, in this work to replace the Sr atom with a P-bloc (Pb) atom in the Li2SrSiS4 compound. According to DFT calculations, the newly designed Li2PbSiS4 compound crystallizes in the stable stannite structure. In addition, it is thermodynamically, dynamically and mechanically stable. The investigated material presents an indirect bandgap of 2.48 eV employing the HSE06 approach, including spin-orbit coupling (SOC) effects. Moreover, the calculated SHG response is 0.85 × AgGaS2, which is larger than the SHG response of Li2SrSiS4. Furthermore, the SHG response increases directly with temperature, allowing using the compound at high temperatures. The obtained results may make the Li2PbSiS4 compound a promising NLO material.