Search results for "Absorption"
showing 10 items of 2701 documents
Ab Initio Simulation of Attosecond Transient Absorption Spectroscopy in Two-Dimensional Materials
2018
We extend the first-principles analysis of attosecond transient absorption spectroscopy to two-dimensional materials. As an example of two-dimensional materials, we apply the analysis to monolayer hexagonal boron nitride (h-BN) and compute its transient optical properties under intense few-cycle infrared laser pulses. Nonadiabatic features are observed in the computed transient absorption spectra. To elucidate the microscopic origin of these features, we analyze the electronic structure of h-BN with density functional theory and investigate the dynamics of specific energy bands with a simple two-band model. Finally, we find that laser-induced intraband transitions play a significant role in…
<title>F-type centers in LiBaF<formula><inf><roman>3</roman></inf></formula> crystals</title>
2003
A comparative study of optical properties of thermochemically reduced undoped LiBaF3 crystals is reported. In LiBaF3 crystals obtained or treated in a reducing atmosphere an absorption band at 240 nm and a corresponding luminescence band at 505 nm are observed at 85 K. The main constituent of the center may be an anion vacancy with a trapped electron (an F-type center in LiBaF3 crystals).© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Self- and air-broadened line shapes in the 2ν3 P and R branches of 12CH4
2015
Abstract In this paper we report line shape parameters of 12 CH 4 for several hundred 2ν 3 transitions in the spectral regions 5891–5996 cm −1 (P branch) and 6015–6115 cm −1 (R branch). Air- and self-broadening coefficients were measured as a function of temperature; line mixing via off-diagonal relaxation matrix element coefficients was also obtained for 47 transition pairs. In total, nearly 1517 positions and intensities were retrieved, but many transitions were too weak for the line shape study. For this analysis, we used 25 high-resolution (0.0056 and 0.0067 cm −1 ) and high signal-to-noise (S/N) spectra of high-purity 12 CH 4 and the same high-purity 12 CH 4 broadened by dry air record…
Erbium-Doped-Silica Photonic Crystal Fiber Characterization Method: Description and Experimental Check
2010
The present paper reports and discusses a characterization method for erbium-doped-silica photonic crystal fibers based on the measurement of pump power attenuation and gain together with the McCumber theory. The absorption and emission cross sections and the passive losses of the fiber were obtained from a fitting procedure of theoretical to experimental values. The method was checked by means of a home-made photonic crystal fiber to verify its reliability. Finally, it was found that the characteristic parameters obtained by this method can be used to accurately simulate the performance of the fiber and therefore to design devices based on it.
<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…