Silicon Nitride Waveguides for Plasmon Optical Trapping and Sensing Applications

TL;DR

This paper presents silicon nitride trench waveguides with integrated bowtie antennas that significantly enhance optical trapping and sensing of nanoparticles through plasmonic effects, combining low-cost fabrication with high performance.

Contribution

The study introduces a novel silicon nitride trench waveguide with integrated plasmonic nanostructures for improved optical trapping and sensing capabilities, demonstrating substantial field enhancement and trapping force.

Findings

60-fold electric field enhancement by bowtie antennas

Boosted optical trapping force by three orders of magnitude

Effective trapping of 10 nm polystyrene nanoparticles

Abstract

We demonstrate a silicon nitride trench waveguide deposited with bowtie antennas for plasmonic enhanced optical trapping. The sub-micron silicon nitride trench waveguides were fabricated with conventional optical lithography in a low cost manner. The waveguides embrace not only low propagation loss and high nonlinearity, but also the inborn merits of combining micro-fluidic channel and waveguide together. Analyte contained in the trapezoidal trench channel can interact with the evanescent field from the waveguide beneath. The evanescent field can be further enhanced by plasmonic nanostructures. With the help of gold nano bowtie antennas, the studied waveguide shows outstanding trapping capability on 10 nm polystyrene nanoparticles. We show that the bowtie antennas can lead to 60-fold enhancement of electric field in the antenna gap. The optical trapping force on a nanoparticle is boosted by three orders of magnitude. A strong tendency shows the nanoparticle is likely to move to the high field strength region, exhibiting the trapping capability of the antenna. Gradient force in vertical direction is calculation by using a point-like dipole assumption, and the analytical solution matches the full-wave simulation well. The investigation indicates that nanostructure patterned silicon nitride trench waveguide is suitable for optical trapping and nanoparticle sensing applications.