Conference Agenda

In modern optical engineering, tunable optical devices play a crucial role in dynamically controlling key optical parameters, enhancing functionality and adaptability. Various mechanisms, such as electrical gating, optical pumping, mechanical actuation, phase transitions, magneto-optical effects, and nanostructured nonlinearities, enable real-time adjustments at the nanoscale level. This facilitates enhanced functionalities like tunable focusing, beam steering, frequency tuning, and polarization control, along with improved imaging and aberration correction in optical systems. A novel approach involves selectively controlling spatial regions for optical tuning, achieved through organic mixed ion-electron conductors like PEDOT:PSS. This conductive polymer offers flexibility, thermal stability, and easy fabrication, with remarkable electrostatic tunability by injecting mobile ionic species from an adjacent electrolyte. By adjusting the bias between electrodes connected to the polymer, full control over material properties can be achieved, enabling the realization of a tunable broadband gradient index material without complex fabrication processes.

Nanosphere lithography is a cost- and time-efficient tool for the fabrication of various nanostructured materials. Multiple steps of metal layer deposition at different oblique angles were shown to produce complex asymmetric and chiral shapes. Here, we investigate samples in which polystyrene nanospheres are covered by Ag or combination of Ag and Au at a single step (under 45°). In this way, we obtain metasurfaces with asymmetric shells, with a nanohole array formed due to the shadowing effect. We investigate chiro-optical properties of four samples by exciting them in the 700-1000 nm range, at angles of incidence from -45° to +45°; we report on dissymmetry in the total extinction between left and right circularly polarized excitation gext, which follows the rules of extrinsic chirality. We then resolve the transmission of Ag metasurface in terms of hyperspectral Stokes parameters, and we connect the S3 parameter with gext. Finally, we characterize nanohole arrays obtained from the same samples when the nanospheres are removed; we further perform electromagnetic simulations to gain insight into the “egg” shaped nanohole.

All-dielectric, sub-micrometric particles obtained through solid state dewetting support Mie resonances together with a high-quality monocrystalline composition. Although the scattering properties of these systems have been qualitatively investigated, a precise study on the impact given by the effective com-plex morphology of a dewetted nanoparticle to the Mie scattering properties is still missing. Here, by us-ing morphological characterization, phase field modelling and light scattering simulation, we provide a realistic modelling of the single scatterer optical properties. Moreover, by means of the Dark-field Scan-ning Optical Microscopy characterizations and numerical simulations of light scattering, we show how the presence of a pedestal enriched with silicon placed under the SiGe-nanoparticle results in a sharp peak at high energy in the total scattering cross-section. Exploiting a tilted illumination to redirect scat-tered light, we can discriminate the spatial localization of the pedestal-induced resonance, extending the practical implementations of dewetted Mie resonators in the field of light scattering directionality and sensing applications.

Multilayered metal-dielectric nanostructures display both strong plasmonic behavior and hyperbolic optical dispersion. The latter is responsible for the appearance of two separated radiative and non-radiative channels in the extinction spectrum of these structures. This unique property can open plenty of opportunities towards the development of multifunctional systems that simultaneously can behave as optimal scatterers and absorbers at different wavelengths, an important feature to achieve multiscale control light-matter interactions in different spectral regions for different types of applications, such as optical computing or detection of thermal radiation. Nevertheless, the temperature dependence of the optical properties of these multilayered systems has never been investigated. In this work, we study how radiative and non-radiative processes in hyperbolic meta-antennas can probe temperature changes of the surrounding medium. We show that, while radiative processes are essentially not affected by a change in the external temperature, the non-radiative ones are strongly affected by a temperature variation. By combining experiments and temperature dependent effective medium theory, we find that this behavior is connected to enhanced damping effects due to electron-phonon scattering. Our study shows that our system can be used as very sensitive thermometers via linear absorption spectroscopy.