MgSiP₂: An Infrared Nonlinear Optical Crystal with a Large Non‐Resonant Phase‐Matchable Second Harmonic Coefficient and High Laser Damage Threshold

Superior infrared nonlinear optical (NLO) crystals are in urgent demand the development of lasers and technologies for communications computing. The critical challenge is to find a crystal with large non-resonant phase-matchable NLO coefficients high laser damage threshold (LDTs) simultaneously, which however scale inversely. This work reports such material, MgSiP2, that exhibits second harmonic generation (SHG) coefficient d14≈d36 = 89 ± 5 pm V−1 at 1550 nm fundamental wavelength, surpassing commercial AgGaS2, AgGaSe2, ZnGeP2. First principles theory reveals polarizability geometric arrangement [SiP4] tetrahedral units as origin this response. Remarkably, it also LDT value 684 GW cm−2, six times larger than ZnGeP2 three CdSiP2. It has wide transparency window 0.53–10.35 µm, allowing broadband tunability. Further, Type I II effective SHG deff,I ≈80.2 deff,II ≈73.4 V−1. outstanding properties MgSiP2 make highly attractive candidate frequency conversion infrared.