Search results for "absorption."
showing 10 items of 2682 documents
<title>Holographic recording in amorphous chalcogenide semiconductor thin films</title>
2000
ABSTRACT The photoinduced changes ofoptical properties and holographic recording in amorphous chalcogenide semiconductor As-S- Se and As2S3 thin films have been studied. The possibilities of the practical applications of these materials as the photoresists for the production of the relief holograms and holographic optical elements are discussed. It is shown that theself-enhancement phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light orthermal treatment can be used to increase the diffraction efficiency ofthe holograms.Keywords: chalcogenide semiconductors, amorphous films, photoresists, photoinduced processes, relaxation processes,self-enhancement of h…
Theoretical and Experimental Researches Regarding Multilayer Materials Used for Incremental Forming
2014
Although this represents a relatively recent development in the industry, the composite multilayer sheets are currently encountered in almost all industrial domains, due to the density, mechanical strength and energy absorption properties that are higher than those of the blanks realised from a single material. These materials are useful especially in domains such a the automotive industry, where the vehicles must fulfil simultaneously conditions of increased passenger safety, increased comfort, increase of the loading capacity in conditions of a reduced energy consumption. First of all the paper shows the types of multilayer sheets and their areas and areas of use, then the paper analyzes …
Characterization of used mineral oil condition by spectroscopic techniques
2004
Optical absorption, fluorescence, and quantitative 13C NMR spectroscopy have been used to study the degradation of mineral gearbox oil. Samples of used oil were collected from field service. Measured absorption, fluorescence, and quantitative 13C NMR spectra of used oils show characteristic changes from the spectra of a fresh oil sample. A clearly observable, approximately 20-nm blueshift of the fluorescence emission occurs during the early stages of oil use and correlates with changes in intensity of some specific 13C NMR resonance lines. These changes correlate with oil age because of the connection between the blueshift and breaking of the larger conjugated hydrocarbons of oil as a resul…
Lateral Size Dependence in FRET between Semiconductor Nanoplatelets and Conjugated Fluorophores
2020
Sensitization of organic molecules by semiconductor nanocrystals is a promising way to boost the absorption of the former, important for applications in fluorescence labeling and photocatalysis. Se...
Near-infrared spatial solitons in heavy metal oxide A glasses
2007
We demonstrate two-dimensional spatial solitons excited by near-infrared picosecond pulses in Kerr-like heavy metal oxide glasses with a nonlinearity one order of magnitude larger than in fused silica. Solitons were obtained at 820 nm owing to the presence of multiphoton absorption, which prevented catastrophic collapse. © 2007 Optical Society of America.
Influence of Cavity Loss Upon Performance of Q-Switched Erbium-Doped Fiber Laser
2013
Performance of an actively Q-switched erbium-doped fiber laser in function of intracavity loss is discussed. We show experimentally and theoretically (employing a distributed model that takes into account two contra-propagating laser waves) that the laser performance strongly depends on the intracavity loss of different kinds. We reveal in particular that the dominant source of smaller than expected pulse energy is the loss via excited-state absorption, inherent in erbium-doped fibers. We also discuss the other important processes involved in active Q-switching, such as passive losses and residual active fiber charge, the impact of which is clarified by a straightforward comparison of the m…
Comparison of impact characteristics of four different ice hockey arena dasher boards
2012
During recent years the incidence of ice hockey related concussions has increased. Therefore, the main aim of this study was to determine how dasher board materials and structures affect impact characteristics and thereby concussion risk. The measurements were divided into two parts; 1. physiological characteristics of body checks were determined in real game measurements, and 2. simulation of body checks in the laboratory. Peak forces and stopping distances were determined from the high-speed camera data, and stiffness values were subsequently calculated. Dasher board materials and structures had a clear effect on impact characteristics. Flexible protective shielding material resulted in 1…
UV photobleaching of carbon nanodots investigated by in situ optical methods.
2020
Carbon dots are a family of optically-active nanoparticles displaying a combination of useful properties that make them attractive for many applications in photonics and photochemistry. Despite the initial claims of high photostability of carbon dots even under prolonged illuminations, several recent studies have evidenced their photobleaching (PB) under UV light, detrimental for some applications. A study of the mechanism and dynamics of carbon dot PB can be considered a useful route to gather relevant information on the underlying photophysics of these nanoparticles, which is still widely debated. Here we report a study of the PB of carbon dots under UV light, conducted through optical ex…
Transition radiation in the x-ray region from a low emittance 855 MeV electron beam
1997
A quasi-monochromatic hard x-ray beam with a photon energy of 33 keV has been produced from transition radiation (TR) at the Mainz Microtron MAMI. The radiator was a stack of 30 polyimide foils of 25 μm thickness and 75 μm separation and the monochromator a highly-oriented pyrolytic graphite crystal. The intrinsic bandwidth was measured with a critical absorption technique to be 100 eV. On the basis of these experiments a photon flux of 4⋅109/mm2s over an illuminated area of 5.7×125 mm2 can be expected from an optimized beryllium radiator at a beam current of 100 μA. At the K-absorption edge of titanium at 5 keV narrow band transition radiation has been observed from a stack of four foils o…
Photocycle of Excitons in Nitrogen-Rich Carbon Nanodots: Implications for Photocatalysis and Photovoltaics
2020
Nitrogen-rich carbon nanodots have emerged as promising nanomaterials for a wide range of applications where a highly emissive and photoactive material with low toxicity and cost-effectiveness is required. One of their hallmarks is indeed a bright, tunable fluorescence of excitonic nature. Disentangling the origin of their optical absorption and fluorescence properties and uncovering relaxation channels and interactions with solvents are some of the most debated issues in the field. Uncovering these aspects is essential for targeted applications, especially in the fields of photocatalysis but also photovoltaics and optoelectronics. Here, we present dedicated transient absorption measurement…