All-optical phase control in nanophotonic silicon waveguides with epsilon-near-zero nanoheaters

A wide variety of nanophotonic applications require controlling the optical phase without changing optical absorption, which in silicon (Si) photonics has been mostly pursued electrically. Here, we investigate the unique light–matter interaction exhibited by epsilon-near-zero (ENZ) materials for all-optical phase control in nanophotonic silicon waveguides. Thermo-optic all-optical phase tuning is achieved using an ENZ material as a compact, low-loss, and efficient optical heat source. For a 10- μ m-long ENZ/Si waveguide, insertion loss below 0.5 dB for the transverse electric (TE) polarization is predicted together with a high control efficiency of ∼ 0.107 π mW - 1 . Our proposal provides a new approach to achieve all-optical, on-chip, and low-loss phase tuning in silicon photonic circuits.