Plasmonic interferometer for nanoscale refractometry

TL;DR

This paper presents a numerical study of a nanoplasmonic interferometer that significantly enhances sensitivity for detecting local refractive index changes by leveraging surface plasmon interference in a double-slit setup.

Contribution

The study introduces a novel plasmonic interferometer design that improves refractometry sensitivity using coupled surface plasmons and farfield interference.

Findings

Significant increase in sensitivity compared to traditional interferometers.

Effective detection of refractive index contrast in nanoscale environments.

Enhanced phase and amplitude signal modification detection.

Abstract

We numerically study a double-slit interferometer that detects the modification of local phase and amplitude signal due to a refractive index contrast in a nanoplasmonic sensor after the plasmonic wave has been coupled to the farfield. Specifically, the sensor consists of two elongated zero-mode waveguides (ZMW) which function to launch surface plasmons as well as transmit light directly into the farfield. The surface plasmon waves are coupled to the farfield by surface gratings which cover one quarter of a bull-eye antenna, with different transmission directions. In the farfield, the coupled plasmon waves interfere with the directly transmitted reference wave, which reveals a combination of the phase and amplitude modification by the asymmetry of refractive index in the lumen of the ZMW. We report a drastic increase in sensitivity over interferometers that only utilize the directly transmitted fraction.