Phase Matching, Strong Frequency Doubling, and Outstanding Laser-Induced Damage Threshold in the Biaxial, Quaternary Diamond-like Semiconductor Li4CdSn2S7

The novel diamond-like Li4CdSn2S7 possesses many outstanding attributes that enable it to be a new, well-rounded front-runner among infrared (IR) nonlinear-optical materials, especially for high-intensity laser applications. Distortions of the metal–sulfur tetrahedra in accordance with Pauling’s second rule give rise to a significant net dipole moment, resulting in a strong second-order nonlinear optical susceptibility (χ(2)) of 35.0 ± 3.5 pm/V. Li4CdSn2S7 possesses an optical bandgap of 2.59 eV and an exceptional laser-induced damage threshold of >2.5 GW/cm2, which is more than 12.5 times greater than that of AgGaSe2 measured under identical irradiation conditions. Li4CdSn2S7 possesses a melting point of ∼780 °C and phase-matchability. All data indicate that Li4CdSn2S7 will outperform AgGaS2 and AgGaSe2 in difference frequency generation schemes for the generation of mid-IR radiation. New information on the recently reported Li2CdSiS4, which Li4CdSn2S7 also outperforms, is additionally included.