Nonlinear refractive index of electric field aligned gold nanorods measured with a Hartmann-Shack wavefront aberrometer

TL;DR

This study measures how the nonlinear refractive index of electric field aligned gold nanorods can be dynamically controlled, revealing a linear dependence on orientation and a 60% variation in nonlinear response.

Contribution

It introduces an experimental method to modulate the nonlinear optical properties of gold nanorods suspensions using electric fields and wavefront sensing.

Findings

Nonlinear refractive index depends linearly on nanorod orientation.

The nonlinear response magnitude can be varied by approximately 60%.

Effective nonlinear index is linked to thermally induced nonlinear effects.

Abstract

The capability to dynamically control the nonlinear refractive index of plasmonic suspensions may enable innovative nonlinear sensing and signaling nanotechnologies. Here, we experimentally determine the effective nonlinear refractive index for gold nanorods suspended in an index matching oil aligned using electric fields, demonstrating an approach to modulate the nonlinear optical properties of the suspension. The nonlinear optical experiments were carried out using a Hartmann-Shack wavefront aberrometer in a collimated beam configuration with a high repetition rate femtosecond laser. The suspensions were probed at 800 nm, overlapping with the long-axis absorption peak of the nanorods. We find that the effective nonlinear refractive index of the gold nanorods suspension depends linearly on the orientational order parameter, S, which can be understood by a thermally induced nonlinear response. We also show the magnitude of the nonlinear response can be varied by ~60%.