Resonant bowtie aperture nano-antenna for the control of optical nanocavities resonance

TL;DR

This paper demonstrates a novel SNOM probe with a bowtie-aperture nano-antenna capable of both redshifting and blueshifting photonic crystal cavity resonances, enabling full postproduction control of optical nanocavities.

Contribution

It introduces a single SNOM probe design that achieves bidirectional tuning of PC cavity resonance through a competition of effects, a novel approach in nanophotonics.

Findings

Achieved resonance shifts up to +0.65nm and -5nm.

Controlled the sign of spectral shifts by adjusting tip-to-PC distance.

Enabled full postproduction tuning of high-Q optical cavities.

Abstract

Scanning Near-field Optical Microscopy (SNOM) has been successful in finely tuning the optical properties of photonic crystal (PC) nanocavities. The SNOM nanoprobes proposed so far allowed for either redshifting or blueshifting the resonance peak of the PC structures. In this Letter, we theoretically demonstrate the possibility of redshifting (up to +0.65nm) and blueshifting (up to $-5$~nm) PC cavity resonance with a single SNOM probe. This probe is obtained by opening a bowtie-aperture nano-antenna (BNA) at the apex of a metal-coated tip. This double-way PC tunability is the result of a competition between the effects of the BNA resonance (induced electric dipole leading to a redshift) and the metal-coated tip (induced magnetic dipole giving rise to a blueshift) onto the PC mode volume. The sign of the spectral shift is modified by simply controlling the tip-to-PC distance. This study opens the way to the full postproduction control of the resonance wavelength of high quality factor optical cavities.