Rainbow-trapping by adiabatic tuning of intragroove plasmon coupling

TL;DR

This paper demonstrates that tuning the width of nano-grooves in subwavelength gratings enables dynamic control of light trapping by manipulating plasmon coupling, with potential applications in tunable optical devices.

Contribution

It introduces a novel approach to light trapping by tuning nano-groove widths, deriving an analytical model, and validating it with numerical simulations for tunable optical functionalities.

Findings

Nano-groove width controls plasmon coupling and light trapping.

Analytical formula matches numerical simulation results.

Tunable nano-groove resonators enable waveguiding and slow-light regimes.

Abstract

It is shown here that rendering the width of nano-grooves into a tunable parameter presents a new means of light trapping in subwavelength gratings. Particularly, in gratings with groove-widths below 150 nm, the plasmon coupling between the perimeter walls of the groove becomes dominant and thus turns groove width into the principle geometric parameter in determining light trapping. Using this parameter, we investigate the prospect of tunable optical functionalities. An analytical formula is derived by treating each nano-groove as a plasmonic waveguide resonator. The resulting change in the cavity effective mode index is examined; these results are in close agreement with numerical simulations. It is shown that the tunable nano-groove resonator presented here accurately defines waveguiding, slow-light, and light-trapping regimes.