Nonlinear optical switching in hybrid plasmonic waveguides

We investigate an optical switching mechanism for applications in active integrated photonic circuits. The mechanism utilizes a large nonlinearity of indium-tin-oxide (ITO) in the epsilon-near-zero regime. The effect of optically induced switching is investigated in hybrid plasmonic waveguides (HPWGs) with an ITO layer that are often used as a platform for various active photonic components, including optical modulators. To study the effect, nonlinear Maxwell equations are solved numerically in time and frequency domains. The all-optical mechanism of switching in HPWGs is quantitatively compared with an electrical gating that is often used to manipulate hybrid modes. It is shown that the optical pumping could potentially cause more efficient switching. The influence of light intensity on HPWG properties and interplay between hybrid modes are investigated numerically in different regimes. Transmittance and phase variation are calculated as a function of light intensity for Si and ${\mathrm{Si}}_3{N}_4$ waveguides. It is shown that the transmittance and its intensity dependence are strongly affected by the ITO thickness. A significant for applications steplike variation of phase and transmittance with intensity is detected. The possibility to control the excitation conditions for surface plasmon polaritons in HPWGs using the active layer of ITO in the nonlinear regime is demonstrated and discussed.