89 research outputs found
Demonstration of fluorescence enhancement: via Bloch surface waves in all-polymer multilayer structures
An all-polymer photonic structure constituted by a distributed Bragg reflector topped with an ultrathin fluorescent polymer film has been studied. A Bloch surface wave resonance has been exploited to improve pumping efficiency. A strongly polarization and angle dependent fluorescence signal is found with respect to the light pumping beam and the emitted wavelength. Matching the most favorable condition for the pump coupling and the collection geometry, the signal obtained from the structure appears to be two orders of magnitude larger than the one of the bare emitting film
Evidence of double-loop hysteresis in disordered ferroelectric crystal
Double-loop electric-field vs polarization hysteresis is investigated in a depoled compositionally disordered lithium-enriched potassium tantalate niobate crystal. Comparing electro-optic response and dielectric spectroscopy indicates that the anomalous response occurs for those temperatures in which the sample also manifests a temperature hysteresis in the low-frequency dielectric function. An electric-field hysteresis at concurrent temperatures suggests an underlying role of reorienting mesoscopic polar regions that accompany the nonergodic phase. Published under license by AIP Publishing
Organic Light-Emitting Transistors in a Smart-Integrated System for Plasmonic-Based Sensing
AbstractThe smart integration of multiple devices in a single functional unit is boosting the advent of compact optical sensors for onâsite analysis. Nevertheless, the development of miniaturized and costâeffective plasmonic sensors is hampered by the strict angular constraints of the detection scheme, which are fulfilled through bulky optical components. Here, an ultracompact system for plasmonicâsensing is demonstrated by the smart integration of an organic lightâemitting transistor (OLET), an organic photodiode (OPD), and a nanostructured plasmonic grating (NPG). The potential of OLETs, as planar multielectrode devices with inherent micrometerâwide emission areas, offers the pioneer incorporation of an OPD onto the source electrode to obtain a monolithic photonic module endowed with lightâemitting and lightâdetection characteristics at unprecedented lateral proximity of them. This approach enables the exploitation of the angleâdependent sensing of the NPG in a miniaturized system based on lowâcost components, in which a reflective detection is enabled by the elegant fabrication of the NPG onto the encapsulation glass of the photonic module. The most effective layout of integration is unraveled by an advanced simulation tool, which allows obtaining an opticsâless plasmonic system able to perform a quantitative detection up to 10â2 RIU at a sensor size as low as 0.1 cm3
Plasmonic Structures for Sensing and Emitting Devices
We report on the study of a plasmonic nanostructure that could be adopted as platform for emitting and sensing applications. Several devices have been prepared and characterized by atomic force microscopy (AFM) and Fourier transform micro-reflectance (FT- pR) techniques. In addition, a modelling via finite-difference time-domain (FDTD) simulations have been developed in order to interpret the morphological shape and the optical response of the considered structures. Until now, remarkable performances as surface plasmon resonance (SPR) based optical sensor have been founded. Moreover, we are performing preliminary trials in order to establish a coupling between photoluminescence (PL) features of suitable emitters with respect to the plasmonic resonances
Field Enhancement by Shaping Nanocavities in a Gold Film
The paper reports on 2D plasmonic crystals composed of
a hexagonal lattice of polymeric nanopillars embedded in
an optically thick gold film on a glass substrate. A tapered
shape of the polymeric pillars is proved to localize the elec-
tric field distribution close to the free surface of the device
and to determine a significant increase in the electric field
intensity particularly when the incident light comes from the
glass side. These effects significantly improve the sample
sensitivity to a refractive index change occurring at the free
surface of the device
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