Search results for "Continuous wave"
showing 10 items of 103 documents
Parametric Frequency Conversion of Short Optical Pulses Controlled by a CW Background
2007
International audience; We predict that parametric sum-frequency generation of an ultra-short pulse may result from the mixing of an ultra-short optical pulse with a quasi-continuous wave control. We analytically show that the intensity, time duration and group velocity of the generated idler pulse may be controlled in a stable manner by adjusting the intensity level of the background pump.
Continuous-wave spontaneous lasing in mercury pumped by resonant two-photon absorption
2010
The first continuous-wave two-photon absorption laser-induced stimulated emission (CTALISE) is demonstrated. The 7^1S-6^1P transition in mercury at 1014nm wavelength is used and selective lasing of different isotopes is observed.
Enhanced quantification of wollastonite and calcite in limestone using fluorescence correction based on continuous wavelet transformation for Raman
2020
Raman spectroscopy offers a nondestructive means to identify minerals in rocks, but the ability to use the technology for quantitative mineralogical analysis is limited by fluorescence that can mask the spectral features of minerals. In this paper we apply continuous wavelet transformation (CWT) to remove fluoresence from Raman data acquired from 26 carbonate rock samples. We then record the intensity values of individual spectral features, proxies for mineral abundances, using the original Raman data and the thus inferred CWT data. The intensity values are then compared against the known mineral abundances determined using the scanning electron microscope (SEM) technology. This comparison …
Signal Restoration via a Splitting Approach
2012
International audience; In the present study, a novel signal restoration method from noisy data samples is presented and is termed as "signal split (SSplit)" approach. The new method utilizes Stein unbiased risk estimate estimator to split the signal, the Lipschitz exponents to identify noise elements and a heuristic approach for the signal reconstruction. However, unlike many noise removal techniques, the present method works only in the non-orthogonal domain. Signal restoration was performed on each individual part by finding the best compromise between the data samples and the smoothing criteria. Statistical results are quite promising and suggest better performance than the conventional…
Parametric frequency conversion of optical simulton pulses
2007
We present an analytical description of the parametric frequency conversion of short solitary wave optical pulses in quadratic nonlinear crystals controlled by means of a continuous wave background.
Extreme Statistics in Raman Fiber Amplifiers: From Analytical Description to Experiments
2011
International audience; In this work, we investigate the emergence of rare and intense events during the Raman fiber amplification of a continuous wave. We highlight how dispersive properties and pump depletion can strongly influence the statistical properties of the amplified signal and its optical spectrum. Under certain conditions, the probability density functions of the amplified signal are calculated analytically and compared with the results of the numerical simulations. The conclusions are qualitatively validated by experiments carried out at telecommunication wavelengths.
Ultraviolet generation in periodically poled Lithium Tantalate waveguides
2008
We demonstrate ultraviolet generation in lithium tantalate channel waveguides for frequency doubling via quasi-phase-matching. The samples, proton exchanged and nanostructured by electric-field assisted surface periodic poling with domains as deep as 40 μm, yield continuous wave light at 365.4 nm with conversion efficiencies larger than 7.5% W-1 cm-2.
Art Painting Testing with Terahertz Pulse and Frequency Modulated Continuous Wave
2017
Paintings of individuals or collections undergo aging over time. The work of art restorers consists of repairing these defects using techniques that respect the history of the work. Ultraviolet, infrared and visible light and X-rays are well known techniques for analyzing these defects, but Terahertz is also increasingly used. Several works have shown that it is possible to detect hidden layers and various defects via terahertz pulses. In a previous work, we have shown that it is possible to use terahertz radiation to detect defects in the context of a restoration of a painting with a speed increase compared to time domain imaging.
Correlation of oscillatory behaviour in Matlab using wavelets
2014
Here we present a novel computational signal processing approach for comparing two signals of equal length and sampling rate, suitable for application across widely varying areas within the geosciences. By performing a continuous wavelet transform (CWT) followed by Spearman?s rank correlation coefficient analysis, a graphical depiction of links between periodicities present in the two signals is generated via two or three dimensional images. In comparison with alternate approaches, e.g., wavelet coherence, this technique is simpler to implement and provides far clearer visual identification of the inter-series relationships. In particular, we report on a Matlab? code which executes this tec…
Consequences of the spatial localization on the exciton recombination dynamics in InGaP/GaAs heterostructures
2002
5 páginas, 4 figuras.