Grain Morphology and Its Influence on Nonlinear Conversion Efficiency of Random Quasi‐Phase Matching in Polycrystalline ZnTe Materials: A Detailed Monte‐Carlo Simulation Study

In polycrystalline materials, random quasi‐phase matching (RQPM) has been regarded as a crucial method for nonlinear optical frequency conversion, particularly in the production of broad bandwidth using femtosecond lasers. Here a second harmonic generation (SHG) is performed in a disordered polycrystalline isotropic material based on the RQPM technique. In this work, a realistic grain growth model has been generated using Neper software for the generation of the second harmonic (SH). The SHG conversion output of every grain size has been analyzed by considering variation in the mean and standard deviation. The random crystal grain orientation has also been considered. The present work also investigates the impacts of fundamental wavelength variation in SH power generation and wideband tuning. The obtained results show that statistical and nonlinear optical laws enhance RQPM theory and provide criteria for polycrystalline material processing for nonlinear applications. Importantly, the wavelength‐dependent response of Zinc Telluride (ZnTe) demonstrates that this morphology‐driven tuning enables selective enhancement of SHG within atmospheric transmission windows (3–5 µ m and extended mid‐infrared (MIR) regions), highlighting its potential for infrared sensing and communication applications. The overall conversion efficiencies using ZnTe crystal as the polycrystalline material are 2.06% for the first model–(a), 2.65% for the second model–(b), and 2.31% for the third model–(c).