Leveraging Epsilon Near Zero phenomena for on-chip photonic modulation

Abstract

Epsilon-near-zero (ENZ) systems exhibit 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 limit the more extraordinary potential of ideal near-zero-index systems. Along with an in-depth discussion on 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.

Figures (23)

• Figure 1: Real and imaginary parts of the refractive index of ITO, CdO and PEDOT:PSS. Vertical lines denote the $\lambda_{ENZ}$, where $n=\kappa$.
• Figure 2: Electric field lines around a dipole oscillator, radiating at $\lambda_{em}$ = 1600 nm, embedded in ENZ media with (a) and (b) $\lambda_{ENZ} < \lambda_{em}$, (c) $\lambda_{ENZ}$ = $\lambda_{em}$ and (d) and (e) $\lambda_{ENZ} > \lambda_{em}$. $\lambda_{ENZ}$ and the $\tilde{n}$ at 1600 nm are mentioned individually. Background color represents log($|\vec{E}|$) as per the colorbar. Plot dimensions: 2.5 $\mu$m$\times$ 2.5 $\mu$m.
• Figure 3: Properties of ENZ media for different values of the damping factor $\gamma$. (a) Radiated power from a point dipole embedded in an unbounded ENZ media. (b) Photon dispersion relation, inset: expanded range demonstrating asymptotic convergence to the light line in the ENZ media for $\omega \rightarrow \infty$. (c) Photon density of states and (d) spectral variation of $v_E/c$, the scatter points shows simulated data and line plot shows analytically calculated data. The blue and white backgrounds demarcate dielectric and metallic regimes of the ENZ and the grey band denotes the spectral range 1600 $\pm$ 10 nm.
• Figure 4: (a) Radiated power transmitted across a ENZ film vs.$\lambda_{ENZ}$. Inset: Schematic of the device with $5$ nm ENZ thinfilm on $SiO_2$ with a point emitter ($\lambda_{em}$=1600 nm) underneath. Magnitude of power flow $(|\vec{S}|)$ (log scale) for various $\lambda_{ENZ}$ (b) 1575 nm, (c) 1600 nm, (d) 1625 nm, scalebar: 200 nm.
• Figure 5: $V_G$ dependence of (a) power transmitted through an ENZ film ($\gamma = 10^{10}$ Hz) and (b) effective refractive index ($n_{eff}$) of the ENZ film with different $\gamma$, for $\lambda_{em}$=1600 nm.