Conference Agenda

Photonic bound states in the continuum (BICs) have enabled a new class of spectrally selective metasurfaces supporting ultrasharp resonances, enabling breakthroughs in higher-harmonic generation, strong light-matter coupling, biodetection, and lasing. However, many implementations still face constraints related to large metasurface footprints, fabrication limits requiring constant resonator heights throughout the structure, or limited numbers of resonances in a given metasurface area. In this talk, I will present some of our recent concepts for obtaining additional nanophotonic functionalities in BIC-driven systems, including the arrangement of resonators in radial configurations for polarization invariance and reduced footprints, height-driven BICs for obtaining maximally chiral light-matter interactions, and active resonance control by incorporating an electro-optically active polymer. Finally, I will show how BIC metasurfaces with continuously varying structural parameters can be leveraged to spatially encode spectral and molecular coupling information simultaneously, enabling new perspectives for biochemical spectroscopy.

Exceptional points (EPs) attract lots of attention due to the richness of the phenomenology associated to their presence in the complex eigenspectrum of coupled non-Hermitian systems. Here we provide both a coupled mode theory analysis and an experimental investigation of two nanolasers interacting through a channel-mediated coupling. We demonstrate the transition from Parity-Time (PT) symmetric to PT-broken regime using a thermo-optic control over the laser frequency detuning. This regime is associated with a significant reduction of the laser threshold as well as we a enhanced sensitivity to external perturbations in the vicinity of the EP.

Our investigation focused on fluorescence enhancement mechanisms using metal nanoantennas with Alexa Fluor-647. By exploiting numerical modelling tools, we fabricated non-interacting Au nanodisc arrays on glass substrates, achieving a maximum fluorescence enhancement factor of 180 at an optimal spacer thickness of approximately 10 nm. Comparative analysis with bare glass substrates revealed significant improvements in excitation and emission dynamics, attributed to nanoscale field confinement and the Purcell effect. Time- and space-resolved photoluminescence measurements unveiled a distance-dependent interaction between the fluorophore and localized plasmons, modulated by thin polyelectrolyte monolayers, with prevalent radiative processes in samples exhibiting maximum signal.

The manipulation of the the field from quantum emitters directly at the source level is becoming an increasingly viable option for obtaining single photons with specific polarizations or phase profiles. In this context, the combination of metasurfaces with surface propagating modes like Bloch Surface Waves have emerged as an ideal candidate. In this work we present a radially distributed metasurface-like grating designed to produce vortex beams with arbitrary spin and orbital angular momentum. This functionality is realized through its synergy with a dipole-like source, coupled with a TM polarized Bloch Surface Wave.

Two dimensional (2D) semiconductors are exceptional materials for exploring light-matter interactions at the nanoscale. Here I will discuss the integration of monolayer semiconductors and hybrid nanophotonic platforms based on Mie-resonant nanostructures, achieving enhanced light-matter interaction up to the strong coupling regime and generation of strain-induced single photon sources.