Date of Award
Spring 5-2026
Document Type
Thesis
Department
Electrical Engineering and Computer Science
First Advisor
Mark C. Harrison, Ph.D.
Second Advisor
Mohamed Allali, Ph.D.
Third Advisor
Maryam Etezadbrojerdi, Ph.D.
Abstract
The growing demand for energy-efficient optical information processing motivates compact nonlinear photonic devices that can operate at low power. Silicon photonics is a mature platform for linear optical functions, but nonlinear operation remains challenging because of its weak Kerr response, two-photon absorption at telecommunication wavelengths, and limited compatibility with deeply subwavelength plasmonic confinement. This thesis computationally investigates epsilon-near-zero thin films integrated into plasmonic waveguide architectures as a route toward stronger light–matter interaction in compact nonlinear devices.
Two waveguide geometries are examined: a hybrid metal-insulator-metal plasmonic slab waveguide incorporating an ultrathin indium tin oxide epsilon-near-zero layer (5–50 nm), and a dielectric-loaded surface plasmon polariton waveguide. Finite element method simulations were performed in COMSOL Multiphysics 6.2 using the Wave Optics Module. Parametric sweeps over epsilon-near-zero layer thickness, metal cladding material, and operating wavelength were used to evaluate effective nonlinear response, propagation loss, and normalized loss-adjusted figures of merit.
For the metal-insulator-metal geometry, thinner epsilon-near-zero layers produced larger effective nonlinear coefficients, with the 5 nm silver–indium tin oxide case reaching 2.66 rad/(W·m) at 1561.1 nm. This enhancement also increased propagation loss, so the useful design space is governed by a trade-off between confinement and attenuation. In the dielectric-loaded surface plasmon polariton geometry, the nonlinear overlap metric peaked near 50 nm indium tin oxide thickness, while the normalized loss-adjusted figure of merit favored thinner layers because loss increased with indium tin oxide thickness.
The simulations identify silver–indium tin oxide metal-insulator-metal structures as strong candidates for high-confinement nonlinear response and dielectric-loaded surface plasmon polariton structures as a more fabrication-accessible alternative with different loss and overlap trade-offs. The main limitation of the present model is that the nonlinear coefficient of indium tin oxide was treated as wavelength independent, so the expected resonant enhancement near the epsilon-near-zero crossing was not fully captured. These results provide a computational baseline for future epsilon-near-zero-integrated nonlinear photonic devices and for follow-up simulations using wavelength-dependent nonlinear material parameters.
DOI
10.36837/chapman.000743
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
K. T. Le, "Designing enhanced nonlinearity in plasmonic devices with epsilon-near-zero films," M. S. thesis, Chapman University, Orange, CA, 2026. https://doi.org/10.36837/chapman.000743
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