Nanoantenna-enhanced ultrafast nonlinear spectroscopy of a single gold nanoparticle

TL;DR

This paper demonstrates the first use of nanoantenna-enhanced ultrafast nonlinear spectroscopy to significantly improve the detection of nonlinear signals from a single gold nanoparticle, enabling new nanoscale investigations.

Contribution

It introduces a novel method combining nanoantennas with ultrafast nonlinear spectroscopy to enhance signals from single nanoobjects, advancing nanoscale optical analysis.

Findings

Signal amplitude increased by an order of magnitude

Good agreement with analytical and numerical models

Potential applications in single-molecule and continuum mechanics studies

Abstract

Optical nanoantennas are a novel tool to investigate previously unattainable dimensions in the nanocosmos. Just like their radio-frequency equivalents, nanoantennas enhance the light-matter interaction in their feed gap. Antenna enhancement of small signals promises to open a new regime in linear and nonlinear spectroscopy on the nanoscale. Without antennas especially the nonlinear spectroscopy of single nanoobjects is very demanding. Here, we present for the first time antenna-enhanced ultrafast nonlinear optical spectroscopy. In particular, we utilize the antenna to determine the nonlinear transient absorption signal of a single gold nanoparticle caused by mechanical breathing oscillations. We increase the signal amplitude by an order of magnitude which is in good agreement with our analytical and numerical models. Our method will find applications in linear and nonlinear spectroscopy of nanoobjects, ranging from single protein binding events via nonlinear tensor elements to the limits of continuum mechanics.