Numerical study of surface plasmon enhanced nonlinear absorption and refraction.

Area of Science:

• Plasmonics
• Nonlinear Optics
• Materials Science

Background:

• Effective medium theories describe composite material properties.
• Silver nanoparticles exhibit surface plasmon resonance, leading to localized field enhancement.
• Kerr-type nonlinear host materials show intensity-dependent refractive index and absorption.

Purpose of the Study:

• To investigate the influence of silver nanoparticle-induced field enhancement on the nonlinear optical response of a Kerr-type host.
• To analyze how surface plasmon resonance affects nonlinear absorption and refractive properties.

Main Methods:

• Application of Maxwell Garnett effective medium theory.
• Analysis of nonlinear absorption coefficient (beta(c)) and linear absorption (alpha(c)).
• Evaluation of the figure of merit (beta(c)/alpha(c)) for nonlinear absorption.

Main Results:

• Composite nonlinear absorption coefficient (beta(c)) is enhanced near silver nanoparticle surface plasmon resonance.
• Enhancement stems from a phase-shifted increase in the host's nonlinear refractive response, not resonant absorption.
• Introduction of linear absorption (alpha(c)) reduces the overall figure of merit.
• Thin (< 1 micrometer) composites show increased nonlinear absorption compared to the host material.

Conclusions:

• Silver nanoparticles can significantly modify the nonlinear optical properties of host materials.
• Surface plasmon enhancement offers a route to boost nonlinear absorption, albeit with trade-offs in linear absorption.
• The findings are particularly relevant for applications utilizing nonlinear optical effects in thin composite films.