Optical nonlinearity enhancement of graded metallic films

TL;DR

This paper theoretically investigates how grading in metallic films enhances optical nonlinearity and surface plasmon resonance effects, providing insights into their potential for improved nonlinear optical applications.

Contribution

It derives exact local field expressions and calculates effective nonlinear susceptibility for graded metallic films with Drude profiles, highlighting the impact of gradation on optical properties.

Findings

Gradation creates a broad plasmon resonance band in the optical region.

Optical nonlinearity and figure of merit are significantly enhanced by gradation.

Theoretical predictions suggest experimental verification is feasible.

Abstract

The effective linear and third-order nonlinear susceptibility of graded metallic films with weak nonlinearity have been investigated. Due to the simple geometry, we were able to derive exactly the local field inside the graded structures having a Drude dielectric gradation profile. We calculated the effective linear dielectric constant and third-order nonlinear susceptibility. We investigated the surface plasmon resonant effect on the optical absorption, optical nonlinearity enhancement, and figure of merit of graded metallic films. It is found that the presence of gradation in metallic films yields a broad resonant plasmon band in the optical region, resulting in a large enhancement of the optical nonlinearity and hence a large figure of merit. We suggest experiments be done to check our theoretical predictions, because graded metallic films can be fabricated more easily than graded particles.