Manipulating Fano coupling in an opto-thermoelectric field

TL;DR

This paper introduces an all-optical method to assemble and reconfigure Fano resonances in nanophotonic structures using a light-driven thermoelectric field, enabling tunable optical properties for spectroscopy.

Contribution

It presents a novel all-optical pick-and-place technique to create reconfigurable Fano metamolecules with tunable coupling and resonance features in dielectric nanostructures.

Findings

Demonstrated tunable Fano resonances in all-dielectric heterodimers.

Achieved control over Fano parameter via light polarization and frequency.

Showed reconfigurable assembly of nanostructures using opto-thermoelectric fields.

Abstract

Fano resonances in photonics arise from the coupling and interference between two resonant modes in structures with broken symmetry. They feature an uneven and narrow and tunable lineshape, and are ideally suited for optical spectroscopy. Many Fano resonance structures have been suggested in nanophotonics over the last ten years, but reconfigurability and tailored design remain challenging. Herein, we propose an all-optical pick-and-place approach aimed at assemble Fano metamolecules of various geometries and compositions in a reconfigurable manner. We study their coupling behavior by in-situ dark-field scattering spectroscopy. Driven by a light-directed opto-thermoelectric field, silicon nanoparticles with high quality-factor Mie resonances (discrete states) and low-loss BaTiO3 nanoparticles (continuum states) are assembled into all-dielectric heterodimers, where distinct Fano resonances are observed. The Fano parameter can be adjusted by changing the resonant frequency of the discrete states or the light polarization. We also show tunable coupling strength and multiple Fano resonances by altering the number of continuum states and discrete states in dielectric heterooligomers. Our work offers a general design rule for Fano resonance and an all-optical platform for controlling Fano coupling on demand.