Light scattering features induced by residual layers in dielectric dewetted nanoparticles

All-dielectric, sub-micrometric particles obtained through solid state dewetting of thin SiGe-films have been shown to support Mie resonances together with a high-quality monocrystalline composition and atomically smooth facets. Recently, a precise study on the impact given by the effective complex morphology of a SiGe dewetted nanoparticle to the Mie scattering properties has been provided and carried on through a novel experimental technique called Dark-field Scanning Optical Microscopy. In this work, by means of the same experimental technique 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 scattered light, we are able to discriminate the spatial localization of the pedestal-induced resonance. Our results contribute to extending the practical implementations of dewetted Mie resonators in the field of light scattering directionality, sensing applications and show further engineering options beyond the simple isolated-island case

Q-Factor Optimization of Modes in Ordered and Disordered Photonic Systems Using Non-Hermitian Perturbation Theory

The quality factor, Q, of photonic resonators permeates most figures of merit in applications that rely on cavity-enhanced light-matter interaction such as all-optical information processing, high-resolution sensing, or ultralow-threshold lasing. As a consequence, large-scale efforts have been devoted to understanding and efficiently computing and optimizing the Q of optical resonators in the design stage. This has generated large know-how on the relation between physical quantities of the cavity, e.g., Q, and controllable parameters, e.g., hole positions, for engineered cavities in gaped photonic crystals. However, such a correspondence is much less intuitive in the case of modes in disordered photonic media, e.g., Anderson-localized modes. Here, we demonstrate that the theoretical framework of quasinormal modes (QNMs), a non-Hermitian perturbation theory for shifting material boundaries, and a finite-element complex eigensolver provide an ideal toolbox for the automated shape optimization of Q of a single photonic mode in both ordered and disordered environments. We benchmark the non-Hermitian perturbation formula and employ it to optimize the Q-factor of a photonic mode relative to the position of vertically etched holes in a dielectric slab for two different settings: first, for the fundamental mode of L3 cavities with various footprints, demonstrating that the approach simultaneously takes in-plane and out-of-plane losses into account and leads to minor modal structure modifications; and second, for an Anderson-localized mode with an initial Q of 200, which evolves into a completely different mode, displaying a threefold reduction in the mode volume, a different overall spatial location, and, notably, a 3 order of magnitude increase in Q.</p

Multimode photonic molecules for advanced force sensing

\u3cp\u3eWe propose a force sensor, with optical detection, based on a reconfigurable multicavity photonic molecule distributed over two parallel photonic crystal membranes. The system spectral behaviour is described with an analytical model based on coupled mode theory and validated by finite difference time domain simulations. The deformation of the upper photonic crystal membrane, due to a localized vertical force, is monitored by the relative spectral positions of the photonic molecule resonances. The proposed system can act both as force sensor, with pico-newton sensitivity, able to identify the position where the force is applied, and as torque sensor able to measure the torsion of the membrane along two perpendicular directions.\u3c/p\u3

Engineering high Q/V photonic modes in correlated disordered systems

Hyperuniform disordered (HuD) photonic materials have recently been shown to display several localized states with relatively high Q factors. However, their spatial position is not predictable a priori. Here we experimentally benchmark through near-field spectroscopy the engineering of high Q/V resonant modes in a defect inside a HuD pattern. These deterministic modes, coexisting with Anderson-localized modes, are a valid candidate for implementations in optoelectronic devices due to the spatial isotropy of the HuD environment upon which they are built

V-ATPase is a candidate therapeutic target for Ewing sarcoma

Suppression of oxidative phosphorylation combined with enhanced aerobic glycolysis and the resulting increased generation of protons are common features of several types of cancer. An efficient mechanism to escape cell death resulting from intracellular acidification is proton pump activation. In Ewing sarcoma (ES), although the tumor-associated chimeric gene EWS-FLI1 is known to induce the accumulation of hypoxia-induced transcription factor HIF-1\u3b1, derangements in metabolic pathways have been neglected so far as candidate pathogenetic mechanisms. In this paper, we observed that ES cells simultaneously activate mitochondrial respiration and high levels of glycolysis. Moreover, although the most effective detoxification mechanism of proton intracellular storage is lysosomal compartmentalization, ES cells show a poorly represented lysosomal compartment, but a high sensitivity to the anti-lysosomal agent bafilomycin A1, targeting the V-ATPase proton pump. We therefore investigated the role of V-ATPase in the acidification activity of ES cells. ES cells with the highest GAPDH and V-ATPase expression also showed the highest acidification rate. Moreover, the localization of V-ATPase was both on the vacuolar and the plasma membrane of all ES cell lines. The acidic extracellular pH that we reproduced in vitro promoted high invasion ability and clonogenic efficiency. Finally, targeting V-ATPase with siRNA and omeprazole treatments, we obtained a significant selective reduction of tumor cell number. In summary, glycolytic activity and activation of V-ATPase are crucial mechanisms of survival of ES cells and can be considered as promising selective targets for the treatment of this tumor

Soft Nano‐Imprint Lithography of Rare‐Earth‐Doped Light‐Emitting Photonic Metasurface

International audienceSol–gel chemistry and nano-imprint lithography (soft-NIL) can be combinedfor the fabrication of nano-patterns with large vertical aspect ratio over largescales. The possibility to frame via soft-NIL metal oxides materials featuringa large refractive index and low absorption coefficient, opens new avenues forlight management. In spite of its importance, the integration of light emittersin these materials has been mostly investigated in flat layers, limiting theirefficiency and versatility. Here it is shown that ZrO 2 can be combined withlight emitting Eu 3+ ions and framed via soft-NIL to form large arrays of pillarsatop a 2D residual layer. The chemical precursor solutions and the nano-imprint technique are developed for photonic metasurfaces sustaining sharpresonances ascribed to quasi-guided modes and lattice modes, as accountedfor by finite difference time domains simulations. These resonances enablefor a record extraction of the Eu 3+ forward emission up to ≈200 times withrespect to the flat counterpart within a relatively small detection angle (≈ ±16°around the vertical direction). These results are relevant for light-emittingdisplays, down- and up-conversion processes for light detection such as scin-tillators for X-ray and for light amplifiers based on rare-earth emitters