Search results for "Optoelectronics"

Poly(alkoxyphenylene-thienylene) Langmuir-Schäfer thin-films for advanced performance transistors

2005

Solution processed Langmuir-Scha ̈fer and cast thin films of regioregular poly(2,5-dioctyloxy-1,4- phenylene-alt-2,5-thienylene) are investigated as transistor active layers. The study of their field-effect properties evidences that no transistor behavior can be seen with a cast film channel material. This was not surprising considering the twisted conformation of the polymer backbone predicted by various theoretical studies. Strikingly, the Langmuir-Scha ̈fer (LS) thin films exhibit a field-effect mobility of 5 × 10-4 cm2/V‚s, the highest attained so far with an alkoxy-substituted conjugated polymer. Extensive optical, morphological, and structural thin-film characterization supports the a…

Influence of Ce codoping and H2 pre-loading on Er/Yb-doped fiber: Radiation response characterized by Confocal Micro-Luminescence

2011

International audience; Confocal microscopy luminescence measurements were applied to study the X-ray radiation response of Er/Yb-doped optical fibers in connection with H2 pre-loading and with the addition of another lanthanide element (Cerium) in the core composition. Laser excitations at 488 nm and 325 nm allow deriving the emission and absorption pattern of Er3+, the latter derived from the dips appearing in a wide luminescence band related to defects in silica. We found that the luminescence spectrum of the X-irradiated Er/Yb-doped core fiber evidences an increase in the emission intensity around 520 and 660 nm; in contrast, no changes are induced by radiation neither after H2 pre-load…

A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer.

2016

The chemical architecture of lanthanide doped core–shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ∼980 to the more relevant ∼808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb–Er co-doped core nanoparticles with the Yb–Nd co-doped shell, we have intentionally combined temperature dependent Er u…

Experimental characterization of Ruthenium-based Dye Sensitized Solar Cells and study of light-soaking effect impact on performance

2016

In this paper, we present an experimental investigation on the performance of Ruthenium-based Dye Sensitized Solar Cells (DSSCs) at different irradiance levels, incident wavelengths and hours of illumination. In particular, the measurements have been aimed at studying the performance variation due to light soaking effect since this phenomenon has noteworthy practical implications, such as stability tests of DSSCs. Our results show that the short circuit current density, the open circuit voltage and the conversion efficiency η increase with the hours of light soaking. Finally, the observed phenomenon is reversible, and thus the performance decreases again when the cell is kept in the dark.

Testing direct neuroprotective effects of current MS therapeutic compounds with intravital two photon laser scanning microscopy

2014

Surface modifications induced by nanosecond pulsed Nd:YAG laser irradiation of metallic substrates

2006

International audience; Substrate surface preparation is a key step in coating deposition process. In recent years, pulsed laser cleaning has emerged as a possible technique to challenge the traditional preparation methods (based on degreasing and eventually grit-blasting). The laser operated at short-pulse mode offers high cleaning efficiency and therefore has been largely used. In a specific process named PROTAL®, a nanosecond pulsed laser is introduced to prepare the surface simultaneously to thermal spraying, with the purpose of eliminating the contaminants and generating favorite surface conditions for coating deposition. This study aims at clarifying some fundamental aspects of nanose…

Resistive switching behaviour in ZnO and VO 2 memristors grown by pulsed laser deposition

2014

The resistive switching behaviour observed in microscale memristors based on laser ablated ZnO and VO 2 is reported. A comparison between the two materials is reported against an active device size. The results show that devices up to 300 × 300 μm 2 exhibit a memristive behaviour regardless of the device size, and 100 × 100 μm 2 ZnO-based memristors have the best resistance off/on ratio.

Application of sol-gel and laser evaporation methods to obtain thin gas sensitive films

2005

New type resistive/capacitative gas sensitive structures were obtained by using a specially prepared substrate- glass, covered by thin conducting In/sub 2/O/sub 3/ layer, cutted into a comb teeth-type electrodes by help of laser beam. Such laser processed gap in the layer of conducting material was a prototype of excellent humidity sensor, especially at high values of relative humidity (RH). Different additional coatings onto a laser processed gap were examined for humidity sensing. Sol-gel, vacuum thermal evaporation and laser evaporation methods were used to obtain a thin layers of different materials.

Generation of Structured Light via Nano Structures and Applications

2020

The generation of structured light by means of metasurfaces is presented and the applications in the characterizations of polarization rotation and Pancharatnam-Berry phase are discussed.

Graded reflectivity micromirror arrays

2002

A technique for fabricating arrays of graded reflectivity micromirrors with diameters as small as 25 microm is reported. It is based on laser-induced physical vapor deposition through microholes on a thin free-standing noncontact mask, and it is suitable for applications in micro-optics and solid-state laser technology.