Search results for "Optoelectronics"
showing 10 items of 2306 documents
Computer simulation of ferroelectric property changes in PLZT ceramics under neutron irradiation
2001
The response of ferroelectric materials to high energy irradiation is of great interest because of their possible application in radiation environments such as thermonuclear reactors. In the present work a physical model for the defect evolution in PLZT ceramics under neutron irradiation and annealing is proposed. The influence of the defect system on the ferroelectric properties of these materials has been investigated. Satisfactory agreement between the theoretical estimated oxygen defect concentration after irradiation and annealing and the experimentally determined polarization has been obtained.
Direct observation of coherent magnons with suboptical wavelengths in a single crystalline ferrimagnetic insulator
2019
In the field of magnetism, spin waves are a subject of great interest for fundamental and application-oriented research. Time-resolved scanning transmission x-ray microscopy, a technique that allows for direct spin-wave imaging below the optical resolution limit, is usually limited to thin layers deposited on x-ray transparent membranes. Here, the authors report on a preparation routine that makes single-crystalline materials accessible to this powerful technique. The latter is subsequently implemented on the ferrimagnetic insulator yttrium iron garnet, where spin waves down to 100-nm wavelength are observed.
Detuning effects in STIRAP processes in the presence of quantum noise
2011
The Stimulated Raman adiabatic passage (STIRAP) in three-state systems in the presence of quantum noise is considered. A comparison is made between different models, one based on a phenomenological introduction of decays, one traceable back to a microscopic description of the system-environment interaction. Effects related, to off-resonance in the coupling between the involved states are considered.
High Resolution Time Domain Reflectometry for Dielectric State Monitoring in High Voltage Cables
2017
A high resolution Time Domain Reflectometry system has been designed in order to investigate the possibility of measuring with good accuracy the dielectric properties of high voltage cables insulator materials by means of Time-of-Flight measures. The system employs a dedicated Time-To-Digital Converter in order to achieve a time resolution of 90 ps. By exploiting averaging techniques the resolution has been further increased. Experimental results showed the possibility of measuring the dielectric constant with a resolution of 0.03%.
Forming-Free and Self-Rectifying Resistive Switching Effect in Anodic Titanium Dioxide-Based Memristors
2018
The paper presents the resistive switching of electroforming-free Ti/anodic- TiO 2 /Cu memristors. Anodic TiO 2 thin films were prepared by anodizing Ti layers. Microscale devices were fabricated by direct laser-assisted photolithography. Experimental results showed a bipolar and self-rectifying behavior of the devices, which could be useful for crossbar array configurations. Moreover, a gradual resistive switching of the devices in both directions was observed, indicating the presence of multi-level resistance states.
Preface to Special Issue of ChemSusChem on Perovskite Optoelectronics
2017
This Editorial introduces one of two companion Special Issues on "Halide Perovskites for Optoelectronics Applications" in ChemSusChem and Energy Technology following the ICMAT 2017 Conference in Singapore. More information on the other Special Issue can be found in the Editorial published in Energy Technology.
Depth profiling of Al2O3 + TiO2 nanolaminates by means of a time-of-flight energy spectrometer
2011
Atomic layer deposition (ALD) is currently a widespread method to grow conformal thin films with a sub-nm thickness control. By using ALD for nanolaminate oxides, it is possible to fine tune the electrical, optical and mechanical properties of thin films. In this study the elemental depth profiles and surface roughnesses were determined for Al2O3 + TiO2 nanolaminates with nominal single-layer thicknesses of 1, 2, 5, 10 and 20 nm and total thickness between 40 nm and 60 nm. The depth profiles were measured by means of a time-of-flight elastic recoil detection analysis (ToF-ERDA) spectrometer recently installed at the University of Jyväskylä. In TOF-E measurements 63Cu, 35Cl, 12C and 4He ions…
Whispering gallery mode resonator sensors referenced to saturated absorption lines in rubidium atoms and a fs frequency comb
2019
Optical Whispering Gallery Mode Resonators (WGMR) can be produced by many methods, for example, by flame melting of silica fibers [1], by polishing of crystals [2], by optical lithography, by solidifying transparent materials, or using commercially available microspheres. They confine light by the total internal reflection and do not need mirror coatings. A part of radiation is traveling outside the WGMR as an evanescent wave and it is used for sensing applications. WGMRs are becoming increasingly popular as biosensors [3] when their surface is covered with antibodies to provide selectivity. Advantage is that light circulates in the resonator and interacts many times with a few molecules at…
Tuneable multicoloured patterns from photonic cross-communication between cholesteric liquid crystal droplets
2014
Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets—which thus act as spherically symmetric self-assembled photonic crystals—and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications.
Emission of Rhodamine B in PMMA opals for luminescent solar concentrators
2012
In conventional luminescent solar concentrators (LSC) incident light is absorbed by luminophores and emitted isotropically. Most of the emitted light is trapped inside the LSC by total internal reflection and guided to solar cells at the edges. Light emitted towards the surfaces, however, is lost in the escape cone. Furthermore, when the luminophore emits light in its absorption range, light is lost due to reabsorption. To overcome these losses, we embed the luminescent material in photonic structures to influence the emission characteristics. Directional and spectral redistribution of emission is supposed to enhance the light guiding in LSCs and reduce reabsorption losses. For this purpose…