Epsilon-near-zero ITO/Ag/SiO 2 metamaterial for large nonlinear absorption

Enhanced nonlinear optical response contributes to higher device efficiency, lower power consumption and more compact integration. In this study, we designed an epsilon-near-zero multilayer metamaterial composed of Ag, ITO and SiO 2 . By enhancing the nonlinear optical response of the material at the epsilon-near-zero wavelength, the saturable absorption behavior has been significantly enhanced ( β = −3.3 × 10 4 cm/GW), which exceeds one order of magnitude when compared to conventional materials such as nanoparticles, two-dimensional materials and so on. Moreover, the strongest nonlinear optical response observed in the annealed multilayer consistently correlates with the redshift of epsilon-near-zero wavelength. Finally, the mechanism underlying saturable absorption is explained through the processes of electronic excitation and relaxation. Our metamaterials can be utilized in saturated absorbers, contributing to the advancement of nonlinear absorption devices.