Hiroki Wadati

<jats:p>The crystal structure of La4Ge3S12 has been known to be noncentrosymmetric for almost four decades. This characteristic inversion symmetry breaking suggests the presence of nonlinear optical (NLO) properties. Yet, experimental observations of such phenomena, including second harmonic generation (SHG) have been reported only in recent studies. In this study, we synthesized La4Ge3S12 using the one‐step melting method, which is more straightforward than the conventional two‐step growth method. We characterized the composition, crystal structure, and electronic structure using electron probe microanalysis, powder X‐ray diffraction, and X‐ray photoelectron spectroscopy. The experimental electronic structure is in line with those obtained using first‐principle calculations. In addition, we observed the NLO properties of La4Ge3S12 in response to the ultrashort pulsed infrared laser. We found that the intensity of the SHG quadratically depends on the intensity of the incident light, mirroring the intrinsic nature of NLO.</jats:p>