In this study, we conduct a comprehensive numerical investigation of nonlinear optical phenomena in three-layer metal–insulator–metal (MIM) plasmonic waveguides, with particular emphasis on the roles of Kerr nonlinearity and self-steepening effects in the 1.55 μm telecommunication band. The analysis is performed by solving the generalized nonlinear propagation equations, taking into account strong field confinement and plasmonic dispersion inherent to MIM geometries. For a gold–silicon nitride–gold configuration, the extracted Kerr nonlinearity is approximately 270 times larger than that of standard silica fiber, while the self-steepening coefficient exhibits an enhancement of nearly 670 times. These pronounced enhancements originate from the combined effects of subwavelength mode confinement and the intrinsic nonlinear response of silicon nitride. The results clearly demonstrate the capability of MIM plasmonic waveguides to significantly boost ultrafast nonlinear interactions over short propagation lengths. Overall, our findings highlight the potential of silicon nitride as a promising material platform for compact MIM plasmonic devices supporting advanced integrated photonic functionalities, including frequency comb generation, supercontinuum expansion, and high-speed optical signal processing.
Attarzadeh et al. (Tue,) studied this question.