Random photonic structures

Exploiting interplay between order and disorder

A suspended Si<sub>3</sub>N<sub>4</sub> membrane.
A suspended Si3N4 membrane.

Recent advances in the engineering of light confinement have demonstrated the ability to fully control the spectral properties of an individual photonic mode in two-dimensional disordered photonic structures, paving the way for the creation of open transmission channels in strongly scattering media. The optical confinement and the coupling between modes open new perspectives over the control of the light flow in random media, as well as the possibility to build architectures tuned for efficient light-matter interaction.

We study a novel geometry, suspended Si3N4 membranes in which the disorder is introduced by shifting the holes by a small normally distributed displacement, to achieve coupling between single quantum emitters (Dibenzoterrylene (DBT) molecules, embedded in a thin anthracene crystals), and disordered photonic structures. In this way, adding disorder on top of an initial ordered structure, we tune the appearance of Anderson localized modes at the proper frequency, for coupling with DBT molecules. Our aim is to study the quasi-modes formation of a disordered pattern to create a chain of hybridized localized modes, extended from one end of the sample to the other. Such topology has the advantage of bringing distant molecules to exchange energy, thanks to the shared photonic mode.

Necklace states

Necklace states are localized modes overlapping both in space and in frequency.
Necklace states are localized modes overlapping both in space and in frequency.

Necklace states arise from the coupling of otherwise confined modes in disordered photonic systems and open high transmission channels in strongly scattering media. Despite their potential relevance in the transport properties of photonic systems, necklace state statistical occurrence in dimensions higher than one is hard to measure, because of the lack of a decisive signature. In this work we provide an efficient method to tell apart in a single measurement a coupled mode from a single localized state in a complex scattering problem, exploiting the analogy with well-characterized coupled cavities in photonic crystals. We study the phase spatial distribution of the electromagnetic field as a function of the coupling strength and of detuning between interacting modes respectively for coupled photonic crystal cavities and for partially disordered systems. Results consistently show that when localized modes spectrally and spatially overlap only over a small surface extent, synchronous oscillation does not build up and the phase spatial distribution splits into two distinct peaks [1].

Amplitude, phase and phase distributions of three localized modes.
Amplitude, phase and phase distributions of three localized modes.

Publications

Other research topics

Single photon sources

Single photon sources

Dibenzoterrylene (DBT) molecules hosted in thin anthracene crystals are a versatile single photon source system. We study their coupling with external nanostructures.

Antennas: Light-shaping and Plasmonics

Antennas: Light-shaping and Plasmonics

Plasmonic structures prove as test beds for studying light-matter interaction at the fundamental level, while versatile hybrid antennas provide excellent means to modulate emission patterns for various applications.

Graphene based nanosensors

Graphene based nanosensors

We envision a new generation of sensors at the nanoscale exploiting different coupling mechanisms between single emitters and a graphene monolayers, such as FRET and Casimir forces.

Transport in turbid media

Transport in turbid media

Monte Carlo simulations provide an exact solution for the Radiative Transfer Equation in turbid media, overcoming the limits of the diffusive approximation.