The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Federico Cilento - One of the best experts on this subject based on the ideXlab platform.
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ultrafast insulator to metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse
Applied Physics Letters, 2010Co-Authors: Federico Cilento, Claudio Giannetti, Gabriele Ferrini, Stefano Dal Conte, Tommaso Sala, G Coslovich, M Rini, A CavalleriAbstract:In this letter we demonstrate the possibility to determine the temporal and spectral structure (spectrogram) of a complex light pulse exploiting the ultrafast switching character of a nonthermal photoinduced phase transition. As a proof, we use a VO2 multifilm, undergoing an ultrafast insulator-to-metal phase transition when excited by femtosecond near-Infrared Laser pulses. The abrupt variation in the multifilm optical properties, over a broad infrared/visible frequency range, is exploited to determine, in situ and in a simple way, the spectrogram of a supercontinuum pulse produced by a photonic crystal fiber. The determination of the structure of the pulse is mandatory to develop pump-probe experiments with frequency resolution over a broad spectral range (700–1100 nm).
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ultrafast insulator to metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse
arXiv: Optics, 2009Co-Authors: Federico Cilento, Claudio Giannetti, Gabriele Ferrini, Stefano Dal Conte, Tommaso Sala, G Coslovich, M Rini, A CavalleriAbstract:In this letter we demonstrate the possibility to determine the temporal and spectral structure (spectrogram) of a complex light pulse exploiting the ultrafast switching character of a non-thermal photo-induced phase transition. As a proof, we use a VO2 multi-film, undergoing an ultrafast insulator-to-metal phase transition when excited by femtosecond near-Infrared Laser pulses. The abrupt variation of the multi-film optical properties, over a broad infrared/visible frequency range, is exploited to determine, in-situ and in a simple way, the spectrogram of a supercontinuum pulse produced by a photonic crystal fiber. The determination of the structure of the pulse is mandatory to develop new pump-probe experiments with frequency resolution over a broad spectral range (700-1100 nm).
Paul Compston - One of the best experts on this subject based on the ideXlab platform.
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optical characterisation and modelling for oblique near infrared Laser heating of carbon fibre reinforced thermoplastic composites
Optics and Lasers in Engineering, 2015Co-Authors: Christopher Stokesgriffin, Paul CompstonAbstract:Abstract The optical behaviour of a carbon fibre reinforced thermoplastic composite material is investigated for a near infrared Laser heating process applied to automated composite tape placement. A nip point heating strategy in Laser tape placement results in a shadow before the nip point on both the incoming tape and substrate. The moderate Laser angle relative to the surface of the composite leads to reflections in the cavity formed by the tape and the substrate, reducing the shadow. An optical ray tracing model can provide valuable insight to the interaction of the Laser with the composite, as well as detailed estimation of the irradiance distributions. This paper provides the foundations for such a model, describing an optical characterisation process and formulation of appropriate models to capture the composite surface and Laser source behaviour. A micro-half-cylinder surface treatment was shown to give a good approximation of the anisotropic scattering behaviour of the composite. Angular dependent reflectance was described well by Fresnel equations. An approximation of the Laser beam profile and propagation is also presented.
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a combined optical thermal model for near infrared Laser heating of thermoplastic composites in an automated tape placement process
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Christopher Stokesgriffin, Paul CompstonAbstract:Abstract A combined optical-thermal model is presented for near-Infrared Laser heating of carbon fibre reinforced thermoplastic composites in an automated tape placement process. For the first time a three dimensional ray tracing model is presented for a near-Infrared Laser tape placement process which captures the unique anisotropic scattering behaviour of the composite. Predicted irradiance distributions on the composite are subsequently applied to a 2D non-linear finite element thermal model. It is shown that a shadow is present in the process and causes a significant drop in temperature prior to the consolidation zone. The effect of various source and surface model simplifications was also studied. The modelled temperature profiles agree well with experimental data. Substrate fibre orientation was investigated and found to have only a small influence on the temperature history.
A Cavalleri - One of the best experts on this subject based on the ideXlab platform.
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ultrafast insulator to metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse
Applied Physics Letters, 2010Co-Authors: Federico Cilento, Claudio Giannetti, Gabriele Ferrini, Stefano Dal Conte, Tommaso Sala, G Coslovich, M Rini, A CavalleriAbstract:In this letter we demonstrate the possibility to determine the temporal and spectral structure (spectrogram) of a complex light pulse exploiting the ultrafast switching character of a nonthermal photoinduced phase transition. As a proof, we use a VO2 multifilm, undergoing an ultrafast insulator-to-metal phase transition when excited by femtosecond near-Infrared Laser pulses. The abrupt variation in the multifilm optical properties, over a broad infrared/visible frequency range, is exploited to determine, in situ and in a simple way, the spectrogram of a supercontinuum pulse produced by a photonic crystal fiber. The determination of the structure of the pulse is mandatory to develop pump-probe experiments with frequency resolution over a broad spectral range (700–1100 nm).
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ultrafast insulator to metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse
arXiv: Optics, 2009Co-Authors: Federico Cilento, Claudio Giannetti, Gabriele Ferrini, Stefano Dal Conte, Tommaso Sala, G Coslovich, M Rini, A CavalleriAbstract:In this letter we demonstrate the possibility to determine the temporal and spectral structure (spectrogram) of a complex light pulse exploiting the ultrafast switching character of a non-thermal photo-induced phase transition. As a proof, we use a VO2 multi-film, undergoing an ultrafast insulator-to-metal phase transition when excited by femtosecond near-Infrared Laser pulses. The abrupt variation of the multi-film optical properties, over a broad infrared/visible frequency range, is exploited to determine, in-situ and in a simple way, the spectrogram of a supercontinuum pulse produced by a photonic crystal fiber. The determination of the structure of the pulse is mandatory to develop new pump-probe experiments with frequency resolution over a broad spectral range (700-1100 nm).
Yasutake Ohishi - One of the best experts on this subject based on the ideXlab platform.
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Laser power density dependent energy transfer between tm 3 and tb 3 tunable upconversion emissions in nayf 4 tm 3 tb 3 yb 3 microcrystals
Optics Express, 2016Co-Authors: Xiaojie Xue, Makhin Thitsa, Tonglei Cheng, Weiqing Gao, Dinghuan Deng, Takenobu Suzuki, Yasutake OhishiAbstract:Energy transfer between Tm3+ and Tb3+ dependent on the power density of pump Laser was investigated in NaYF4: Tb3+,Tm3+,Yb3+ microcrystals. Under the excitation of a 976-nm near-Infrared Laser at various power densities, Tb3+-Tm3+-Yb3+ doped samples exhibited intense visible emissions with tunable color between green and blue. The ratio of blue and green emission were determined by energy transfer between Tm3+ and Tb3+. When the power density of pump Laser was low, the energy transfer process from Tm3+ (3F4) to Tb3+ (7F0) occurred efficiently. Upconversion processes in Tm3+ were inhibited, only visible emissions from Tb3+ with green color were observed. When the power density increased, energy transfer from the 3F4 (Tm3+) to 7F0 level (Tb3+) was restrained and population on high energy levels of Tm3+ was increased. Contribution of upconversion emissions from Tm3+ gradually became dominant. The emission color was tuned from green to blue with increasing the power density. Energy transfer processes between low-lying levels of activators, such as Tm3+ will greatly reduce the population on certain levels for further high-order upconversion processes. The Tb3+-Tm3+-Yb3+ doped phosphors are promising materials for detecting the condition of power density of the invisible near-Infrared Laser.
G Coslovich - One of the best experts on this subject based on the ideXlab platform.
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ultrafast insulator to metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse
Applied Physics Letters, 2010Co-Authors: Federico Cilento, Claudio Giannetti, Gabriele Ferrini, Stefano Dal Conte, Tommaso Sala, G Coslovich, M Rini, A CavalleriAbstract:In this letter we demonstrate the possibility to determine the temporal and spectral structure (spectrogram) of a complex light pulse exploiting the ultrafast switching character of a nonthermal photoinduced phase transition. As a proof, we use a VO2 multifilm, undergoing an ultrafast insulator-to-metal phase transition when excited by femtosecond near-Infrared Laser pulses. The abrupt variation in the multifilm optical properties, over a broad infrared/visible frequency range, is exploited to determine, in situ and in a simple way, the spectrogram of a supercontinuum pulse produced by a photonic crystal fiber. The determination of the structure of the pulse is mandatory to develop pump-probe experiments with frequency resolution over a broad spectral range (700–1100 nm).
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ultrafast insulator to metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse
arXiv: Optics, 2009Co-Authors: Federico Cilento, Claudio Giannetti, Gabriele Ferrini, Stefano Dal Conte, Tommaso Sala, G Coslovich, M Rini, A CavalleriAbstract:In this letter we demonstrate the possibility to determine the temporal and spectral structure (spectrogram) of a complex light pulse exploiting the ultrafast switching character of a non-thermal photo-induced phase transition. As a proof, we use a VO2 multi-film, undergoing an ultrafast insulator-to-metal phase transition when excited by femtosecond near-Infrared Laser pulses. The abrupt variation of the multi-film optical properties, over a broad infrared/visible frequency range, is exploited to determine, in-situ and in a simple way, the spectrogram of a supercontinuum pulse produced by a photonic crystal fiber. The determination of the structure of the pulse is mandatory to develop new pump-probe experiments with frequency resolution over a broad spectral range (700-1100 nm).
