Speaker
Description
We demonstrate that post-deposition annealing provides an effective route to spectrally engineer the nonlinear optical response of indium tin oxide (ITO) thin films, with a pronounced enhancement at technologically relevant telecommunication wavelengths. Annealing-induced modifications to the epsilon‑near‑zero (ENZ) wavelength enable controlled spectral shifting of the material’s nonlinear response, resulting in a substantial improvement of the nonlinear absorption near 1550 nm. While the peak nonlinear response is reduced, annealing redistributes the nonlinearity over a broader spectral range, yielding enhanced performance across the near‑infrared. Spectroscopic ellipsometry reveals a complex permittivity response that cannot be captured by a simple Drude model, indicating the emergence of non‑Drude contributions to the optical behavior. Atomic force microscopy further suggests that these changes correlate with annealing-driven morphological evolution of the films. Our findings show that although spectral broadening ultimately limits the tunability of the wavelength corresponding to maximal nonlinearity, post‑annealing enables a significant and robust enhancement of the nonlinear response of ITO at 1550 nm, positioning it as a promising platform for nonlinear nanophotonic and telecom-scale applications.
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