Microresonator dynamics with frequency-dependent Kerr nonlinearity

Abstract

We investigate the ultrafast nonlinear dynamics in a silica ringresonator composed of a silver-nanoparticle-doped core that exhibits rapidly varying frequency-dependent Kerr nonlinearity that even changes sign across a specific frequency, defined as zero-nonlinearity frequency. We model optical propagation in such a resonator through a modified Lugiato-Lefever equation, revealing that the formation of bright cavity solitons can be possible in both positive and negative nonlinearity domains. The intrapulse Raman scattering along with the frequency-dependent Kerr nonlinearity modify the stability and the dynamics of cavity solitons, which we analyze using a bistability analysis, intracavity modulation-instability analysis, and semianalytical variational approach. Our derived analytical results agree well with the direct numerical solutions of the Lugiato-Lefever equation. The generation of a dispersive wave from a cavity soliton encountering higher-order dispersion is also influenced by the location of the zero-nonlinearity frequency, which we describe by providing a modified phase matching equation. Our results and analysis provide a framework for better understanding the dynamics of cavity solitons and their interactions in two different bright-solitonic domains with possible applications in dual-pump spectroscopy, formation of soliton molecules, and counterpropagating solitons to other fields.