Quasinormal-mode modeling and design in nonlinear nano-optics

Based on quasinormal-mode theory, we propose a novel approach enabling a deep analytical insight into the multi-parameter design and optimization of nonlinear photonic structures at subwavelength scale. A key distinction of our method from previous formulations relying on multipolar Mie-scattering expansions is that it directly exploits the natural resonant modes of the nanostructures, which provide the field enhancement to achieve significant nonlinear efficiency. Thanks to closed-form expression for the nonlinear overlap integral between the interacting modes, we illustrate the potential of our method with a two-order-of-magnitude boost of second harmonic generation in a semiconductor nanostructure, by engineering both the sign of $\chi^{(2)}$ at subwavelength scale and the structure of the pump beam

Metric measure spaces with Riemannian Ricci curvature bounded from below

In this paper we introduce a synthetic notion of Riemannian Ricci bounds from below for metric measure spaces (X,d,m) which is stable under measured Gromov-Hausdorff convergence and rules out Finsler geometries. It can be given in terms of an enforcement of the Lott, Sturm and Villani geodesic convexity condition for the entropy coupled with the linearity of the heat flow. Besides stability, it enjoys the same tensorization, global-to-local and local-to-global properties. In these spaces, that we call RCD(K,\infty) spaces, we prove that the heat flow (which can be equivalently characterized either as the flow associated to the Dirichlet form, or as the Wasserstein gradient flow of the entropy) satisfies Wasserstein contraction estimates and several regularity properties, in particular Bakry-Emery estimates and the L^\infty-Lip Feller regularization. We also prove that the distance induced by the Dirichlet form coincides with d, that the local energy measure has density given by the square of Cheeger's relaxed slope and, as a consequence, that the underlying Brownian motion has continuous paths. All these results are obtained independently of Poincar\'e and doubling assumptions on the metric measure structure and therefore apply also to spaces which are not locally compact, as the infinite-dimensional onesComment: (v2) Minor typos, proof of Proposition 2.3, proof of Theorem 4.8: corrected. Proof of Theorem 6.2: corrected and simplified, thanks to the new Lemma 2.8. Lemma 3.6 and 4.6 (of v1) removed, since no more neede

Microfluidic behaviour of perfluoropolyether fluids in poly(dimethylsiloxane) micro-channels

Two different perfluoropolyether-based fluids, namely the unfunctionalized GALDEN SV90® and the dihydroxy derivative FOMBLIN Z-DOL® 2000 were employed as liquid samples in a poly(dimethylsiloxane) (PDMS) microfluidic setup, fabricated by soft-lithography techniques. The results of our investigation were compared with the behaviour of the low viscosity and high-fragility polyurethane structural adhesive (NOA72®), that is well known as an excellent material for the fabrication of sub-micrometer structures by soft-lithography techniques, and whose structural elastic properties inside restricted geometric systems have been recently investigated

Rigid organic molds for nanoimprint lithography by replica molding of high glass transition temperature polymers

The glass transition of polycarbonate resins of high softness temperature is exploited to realize rigid polymeric replicas of master patterns, with no need for antisticking layers and applied pressure. Such replicas enable the transfer of patterns onto polymers having a lower glass-transition temperature by nanoimprint lithography. As a demonstration, we show the pattern transfer onto poly(methylmethacrylate), which demonstrates good fidelity and remarkable simplicity of the process

Endocannabinoid-related compounds in gastrointestinal diseases

The endocannabinoid system (ECS) is an endogenous signalling pathway involved in the control of several gastrointestinal (GI) functions at both peripheral and central levels. In recent years, it has become apparent that the ECS is pivotal in the regulation of GI motility, secretion and sensitivity, but endocannabinoids (ECs) are also involved in the regulation of intestinal inflammation and mucosal barrier permeability, suggesting their role in the pathophysiology of both functional and organic GI disorders. Genetic studies in patients with irritable bowel syndrome (IBS) or inflammatory bowel disease have indeed shown significant associations with polymorphisms or mutation in genes encoding for cannabinoid receptor or enzyme responsible for their catabolism, respectively. Furthermore, ongoing clinical trials are testing EC agonists/antagonists in the achievement of symptomatic relief from a number of GI symptoms. Despite this evidence, there is a lack of supportive RCTs and relevant data in human beings, and hence, the possible therapeutic application of these compounds is raising ethical, political and economic concerns. More recently, the identification of several EC-like compounds able to modulate ECS function without the typical central side effects of cannabinomimetics has paved the way for emerging peripherally acting drugs. This review summarizes the possible mechanisms linking the ECS to GI disorders and describes the most recent advances in the manipulation of the ECS in the treatment of GI diseases

Bright White‐Light‐Emitting Device from Ternary Nanocrystal Composites

A hybrid white-light-emitting device (see figure) whose emission originates only from ternary nanocrystal (quantum dot) composites but whose luminance performance matches the requirements of the lighting industry is demonstrated. The bright white-light emission is obtained by controlling the Forster energy transfer and charge-trapping mechanisms between the different components

Microfluidic motion for a direct investigation of the structural dynamics of glass-forming liquids.

Glass-forming liquids, polymer solutions, and biofluids have additional inertial and elastic macroscopic degrees of freedom that are related to the elasticity of the molecular coils and affect the determination of the structural dynamical parameters. In this work, we propose a new approach for the direct evaluation of the fundamental material parameters (viscosity, fragility, glass transition temperature) of a viscoelastic liquid in a capillary flow inside a microfluidic device. The proposed technique substantially reduces the complexity of the theoretical analysis and provides an evaluation of the most relevant functional parameters of the fluid dynamics. Moreover, the approach allows the investigation of localization phenomena in geometrical confined systems, such as those required in miniaturized devices

White-light-emitting diodes using semiconductor nanocrystals

Light-emitting diodes (LEDs) based on colloidal inorganic semiconductor nanocrystals (QDs) represent a completely new technology platform for the development of flat-panel displays and flat-panel lighting systems. Their major advantages are the easy tuning of the saturated color emission across the visible-NIR range and the high chemical and optical stability of the nanocrystal composites. These characteristics open the way to a new class of hybrid devices in which the low cost, flexible technology of organic LEDs is combined with the long operating lifetime of inorganic semiconductor devices. However, so far, few studies have been reported on white-LEDs based on QDs. This review shows recent developments in the general method for the fabrication of stable white-LEDs comprising QDs with a potentially long lifetime