Room temperature Bloch surface wave polaritons

Polaritons are hybrid light-matter quasi-particles that have gathered a significant attention for their capability to show room temperature and out-of-equilibrium Bose-Einstein condensation. More recently, a novel class of ultrafast optical devices have been realized by using flows of polariton fluids, such as switches, interferometers and logical gates. However, polariton lifetimes and propagation distance are strongly limited by photon losses and accessible in-plane momenta in usual microcavity samples. In this work, we show experimental evidence of the formation of room temperature propagating polariton states arising from the strong coupling between organic excitons and a Bloch surface wave. This result, which was only recently predicted, paves the way for the realization of polariton devices that could allow lossless propagation up to macroscopic distances

Ultrafast flow of interacting organic polaritons

The strong-coupling of an excitonic transition with an electromagnetic mode results in composite quasi-particles called exciton-polaritons, which have been shown to combine the best properties of their bare components in semiconductor microcavities. However, the physics and applications of polariton flows in organic materials and at room temperature are still unexplored because of the poor photon confinement in such structures. Here we demonstrate that polaritons formed by the hybridization of organic excitons with a Bloch Surface Wave are able to propagate for hundreds of microns showing remarkable third-order nonlinear interactions upon high injection density. These findings pave the way for the studies of organic nonlinear light-matter fluxes and for a technological promising route of dissipation-less on-chip polariton devices working at room temperature.Comment: Improved version with polariton-polariton interactions. 13 pages, 4 figures, supporting 6 pages, 6 figure

Interactions and scattering of quantum vortices in a polariton fluid

Quantum vortices, the quantized version of classical vortices, play a prominent role in superfluid and superconductor phase transitions. However, their exploration at a particle level in open quantum systems has gained considerable attention only recently. Here we study vortex pair interactions in a resonant polariton fluid created in a solid-state microcavity. By tracking the vortices on picosecond time scales, we reveal the role of nonlinearity, as well as of density and phase gradients, in driving their rotational dynamics. Such effects are also responsible for the split of composite spin-vortex molecules into elementary half-vortices, when seeding opposite vorticity between the two spinorial components. Remarkably, we also observe that vortices placed in close proximity experience a pull-push scenario leading to unusual scattering-like events that can be described by a tunable effective potential. Understanding vortex interactions can be useful in quantum hydrodynamics and in the development of vortex-based lattices, gyroscopes, and logic devices.Comment: 12 pages, 7 figures, Supplementary Material and 5 movies included in arXi

Sub-50-nm conjugated polymer dots by nanoprinting.

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Brain Response to Antismoking PSA, an EEG Study

Public service antismoke announcements (PSA) are essential tools for promoting messages worthy of society. In 2015 the Italian Government released an anti-smoking PSA to raise young people’s awareness of the smoking dangers. To demonstrate the effectiveness of that campaign, the present study investigated the mental response of 56 participants while watching the PSA through the Electroencephalogram (EEG). The EEG is frequently employed in neuromarketing to face the limitations of verbal declarations, allowing to evaluate the advertisings’ efficacy objectively. The present study analyzed the PSA, considering the smoking habit of participants by dividing them into smokers and nonsmokers. Some main segments of the PSA were identified and separately analyzed for evidencing the most effective part for the anti-smoking message. Three main EEG indexes have been explored in the analysis: mental engagement index (ME), spectral asymmetry index (SASI), and the mental effort index. The t-test performed on the index values showed an increase of the ME and the SASI for smokers compared to non-smokers (p<0.005). While the repeated measures ANOVA pointed out that the indexes were differently modulated by the parts of the PSA, showing the effectiveness of the smoking symptoms’ description and the claim at the brain level