The promise of active nanophotonics technology relies on the confinement and control of light at the nanoscale. Confinement via plasmonics, dielectric resonators, and waveguides can be complemented with materials whose optical properties can be controlled using nonlinear effects. Transparent conducting oxides (TCOs) exhibit strong optical nonlinearities in their near zero permittivity spectral region, on the femtosecond

The promise of dynamic nanophotonic technologies relies on the confinement and spatiotemporal control of light at the nanoscale. Confinement via plasmonics, dielectric resonators, and waveguides can be complemented with materials whose optical properties can be controlled using nonlinear effects. Transparent conducting oxides (TCOs) exhibit strong optical nonlinearities in their near‐zero permittivity spectral region, on the femtosecond timescale. Harnessing full spatiotemporal control over the nonlinear response requires a deeper understanding of the process. To achieve this, a self‐consistent multiphysics time‐domain model for the nonlinear optical response of TCOs is developed and implemented into a 3D finite‐difference time‐domain code. Simulations are compared and tuned against recently published experimental results for intense laser irradiation of thin indium tin oxide (ITO) films, achieving good quantitative agreement; the time‐domain dynamics of the nonlinear response and the phenomenon of time‐refraction are also explored. Finally, by simulating intense laser irradiation of a plasmonic particle on an ITO film, the applicability of the approach to time‐varying metasurfaces is demonstrated. As expected, significant enhancement of the nonlinear response of an ITO‐based metasurface over bare ITO thin films is found. This work thus enables quantitative nanophotonics design with conductive oxides in their epsilon‐near‐zero region.

Changing the frequency of light outside the laser cavity is essential for an integrated photonics platform, especially when the optical frequency of the on-chip light source is fixed or challenging to be tuned precisely. Previous on-chip frequency conversion demonstrations of multiple GHz have limitations of tuning the shifted frequency continuously. To achieve continuous on-chip optical frequency conversion, we electrically tune a lithium niobate ring resonator to induce adiabatic frequency conversion. In this work, frequency shifts of up to 14.3 GHz are achieved by adjusting the voltage of an RF control. With this technique, we can dynamically control light in a cavity within its photon lifetime by tuning the refractive index of the ring resonator electrically.

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