Dynamics of four-photon photoluminescence in gold nanoantennas

TL;DR

This study investigates the temporal dynamics of two- and four-photon photoluminescence in gold nanoantennas, revealing a unified model for their generation and demonstrating control over emission processes via laser pulse duration.

Contribution

It introduces a comprehensive model explaining multiphoton photoluminescence in gold nanoantennas and shows how to selectively induce 2PPL or 4PPL by adjusting laser pulse duration.

Findings

4PPL involves a three-photon interband transition.

4PPL is favored over other multiphoton processes below damage threshold.

Pulse duration controls the dominance of 2PPL or 4PPL.

Abstract

Two-pulse correlation is employed to investigate the temporal dynamics of both two-photon photoluminescence (2PPL) and four-photon photoluminescence (4PPL) in resonant and nonresonant nanoantennas excited at a wavelength of 800 nm. Our data are consistent with the same two-step model being the cause of both 4PPL and 2PPL, implying that the first excitation step in 4PPL is a three-photon sp->sp direct interband transition. Considering energy and parity conservation, we also explain why 4PPL behavior is favored over three-and five-photon photoluminescence in the power range below the damage threshold of our antennas. Since sizeable 4PPL requires larger peak intensities of the local field, we are able to select either 2PPL or 4PPL in the same gold nanoantennas by choosing a suitable laser pulse duration. We thus provide a first consistent model for the understanding of multiphoton photoluminescence generation in gold nanoantennas, opening new perspectives for applications ranging from the characterization of plasmonic resonances to biomedical imaging.