A scanning planar Yagi-Uda antenna for fluorescence detection

TL;DR

This paper presents a novel scanning planar Yagi-Uda antenna that enhances fluorescence detection by directing emitted light into a narrow cone, significantly increasing signal collection efficiency for nanoscale light sources.

Contribution

It introduces and experimentally investigates a scanning implementation of a planar antenna, demonstrating control over radiation pattern and improved fluorescence signal collection.

Findings

Beams light into a 45° cone with FWHM

Increases collected signal by over 3 times

Modifies light-matter interaction for sensing and imaging

Abstract

An effective approach to improve the detection efficiency of nanoscale light sources relies on a planar antenna configuration, which beams the emitted light into a narrow cone. Planar antennas operate like optical Yagi-Uda antennas, where reflector and director elements are made of metal films. Here we introduce and investigate, both theoretically and experimentally, a scanning implementation of a planar antenna. Using a small ensemble of molecules contained in fluorescent nanobeads placed in the antenna, we independently address the intensity, the radiation pattern and the decay rate as a function of distance between a flat-tip scanning gold wire (reflector) and a thin gold film coated on a glass coverslip (director). The scanning planar antenna changes the radiation pattern of a single fluorescent bead and it beams light into a narrow cone down to angles of 45{\deg} (full width at half maximum). Moreover, the collected signal compared to the case of a glass coverslip is larger than a factor of 3, which is mainly due to the excitation enhancement. These results offer a better understanding of the modification of light-matter interaction by planar antennas and they hold promise for applications, such as sensing, imaging and diagnostics.