Hybrid Metal-Dielectric Plasmonic Zero Mode Waveguide for Enhanced Single Molecule Detection

TL;DR

This paper reports the fabrication and optical characterization of hybrid metal-dielectric nanoantennas functioning as enhanced Zero Mode Waveguides, demonstrating their potential for single-molecule detection with wavelength-dependent performance.

Contribution

It introduces a novel hybrid metal-dielectric nanoantenna design that improves single-molecule detection capabilities compared to traditional gold ZMWs.

Findings

Enhanced fluorescence and reduced detection volume at specific wavelengths

Wavelength blue-shift reduces nanoantenna performance

Dielectric silicon layer improves nanoantenna design

Abstract

We fabricated hybrid metal-dielectric nanoantennas and measured their optical response at three different wavelengths. The nanostructure is fabricated on a bilayer film formed by the sequential deposition of silicon and gold on a transparent substrate. The optical characterization is done via fluorescence measurements. We characterized the fluorescence enhancement, as well as the lifetime and detection volume reduction for each wavelength. We observe that the hybrid metal-dielectric nanoantennas behave as enhanced Zero Mode Waveguides in the near-infrared spectral region. Their detection volume is such that they can perform enhanced single-molecule detection at tens of microM. However, a wavelength blue-shift of 40 nm dramatically decreases the performance of the nanoantennas. We compared their behavior with that of a golden ZMW, and we verified that the dielectric silicon layer improves the design. We interpreted the experimental observations with the help of numerical simulations. In addition, the simulations showed that the field enhancement of the structure highly depends on the incoming beam: tightly focused beams yield lower field enhancements than plane-waves.