Photonic meta-atoms in media with a frequency-dependent nonlinearity

We study photonic meta-atoms in media with a zero-nonlinearity wavelength (ZNW). We show that the Raman self-frequency shift experienced by these bound compounds, formed by an intense soliton and a trapped weak pulse, is strongly dependent on the actual position of the ZNW. Moreover, the amount of trapped energy is shown to depend on the position of the ZNW, causing these two-color compounds to be unstable whenever the ZNW lies close to the weak pulse wavelength. Finally, simulation results obtained with the photon-conserving Generalized Nonlinear Schrödinger Equation (pcGNLSE) are shown to differ significantly from those obtained with the conventional GNLSE. Most strikingly, whenever the ZNW lies in between the soliton and weak pulse wavelengths, the pcGNLSE predicts that no stable compounds can be formed, contrary to the GNLSE.