Leveraging epsilon-near-zero phenomena for on-chip photonic modulation

Epsilon-near-zero (ENZ) systems exhibit an unconventional electromagnetic response close to their zero-permittivity regime. Here, we explore the ability of ultrathin ENZ films to modulate the transmission of radiation from an underlying quantum emitter through active control of the carrier density of the ENZ film. The achievable on-off switching ratio is shown to be constrained by the material's loss parameter, particularly in the ENZ regime, where transmissivity increases with higher material loss. The finite loss in real materials limits the more extraordinary potential of ideal near-zero-index systems. Along with an in-depth discussion of the material parameters vis-\`a-vis the underlying physics, this work provides avenues to overcome the shortcomings of finite loss in real materials. These findings are intended to guide material development and offer valuable insights for designing on-chip optical modulators and beam steering devices operating in the near-infrared regime.