The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Xiuhua Yuan - One of the best experts on this subject based on the ideXlab platform.
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Investigation of superstructured fiber Bragg grating-based OCDMA system
Photonic Network Communications, 2010Co-Authors: Xiaogang Chen, Xiuhua YuanAbstract:The bit error rate (BER) performance of a superstructured fiber Bragg grating (SSFBG)-based optical code division multiple access (OCDMA) system is investigated with different Input Pulse widths and grating refractive index modulation amplitudes, and the corresponding crosstalk ratio is considered at different data-rates. Simulation results show that increasing the Input Pulse width or grating refractive index modulation amplitude will degrade the BER performance apparently. Moreover, with fixed code length and chip-rate detection, a lower data-rate system has better tolerance to an increasing Input Pulse width, while a higher data-rate system has better tolerance to an increasing grating refractive index modulation amplitude.
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Crosstalk performance of coherent time-spreading OCDMA system based on superstructured fiber Bragg grating
2010 International Conference on Display and Photonics, 2010Co-Authors: Xiaogang Chen, Xiuhua YuanAbstract:The crosstalk performance of coherent time-spreading OCDMA system based on superstructured fiber Bragg grating (SSFBG) is investigated with different Input Pulse width and grating refractive index modulation amplitude, and corresponding bit error rate (BER) performance was considered at different data-rate. Simulation results show that the crosstalk performance will be degraded with the increasing of Input Pulse width or grating refractive index modulation amplitude. Moreover, with fixed code length N = 127 and receiver bandwidth limitation, lower data-rate system has better tolerance to the increasing of Input Pulse width, while higher data-rate system has better tolerance to the increasing of grating refractive index modulation amplitude.
Arnaud Couairon - One of the best experts on this subject based on the ideXlab platform.
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Second-order cascading-assisted filamentation and controllable supercontinuum generation in birefringent crystals
Optics Express, 2017Co-Authors: Rosvaldas Suminas, Vytautas Jukna, Arnaud Couairon, Gintaras Tamosauskas, Audrius DubietisAbstract:We experimentally investigate filamentation and supercontinuum generation in a birefringent medium (BBO crystal), in the self-focusing regime where intrinsic cubic nonlinearity is either enhanced or reduced by the second-order cascading due to phase-mismatched second harmonic generation. We demonstrate that the supercontinuum spectral extent is efficiently controlled by varying the phase mismatch parameter. In the range of negative phase mismatch, we achieve full control of the blue-shifted spectral broadening, which is very robust and independent on the Input Pulse energy. In the range of positive phase mismatch, both the blue-shifted and the red-shifted spectral broadenings are controlled simultaneously, however showing a certain dependence on the Input Pulse energy. The results are interpreted in terms of complex interplay between the self-phase-matched second harmonic generation, which is a process inherent to narrow ultrashort Pulsed laser beams and concurrent self-steepening processes which arise from cubic and cascaded-quadratic nonlinearities.
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Effect of Input Pulse chirp on nonlinear energy deposition and plasma excitation in water
Journal of the Optical Society of America B, 2014Co-Authors: Carles Milián, Amélie Jarnac, Yohann Brelet, Vytautas Jukna, Aurélien Houard, André Mysyrowicz, Arnaud CouaironAbstract:We analyze numerically and experimentally the effect of the Input Pulse chirp on the nonlinear energy transfer from 5 µJ fs-Pulses at 800 nm to water. Numerical results are also shown for Pulses at 400 nm, where linear losses are minimized, and for different focusing geometries. Input chirp is found to have a big impact on the transmitted energy and on the plasma distribution around focus, thus providing a simple and effective mechanism to tune the electron density and energy deposition. We identify three relevant ways in which plasma features may be tuned.
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Generation of long plasma channels in air by focusing ultrashort laser Pulses with an axicon
Optics Communications, 2009Co-Authors: Selcuk Akturk, Arnaud Couairon, Bing Zhou, Michel Franco, André MysyrowiczAbstract:We show that by focusing ultrashort-Pulsed laser beams in air with an axicon, relatively long plasma channels can be generated. The axicon generates Bessel-like beams, where the on-axis intensity stays high over distances much longer compared to focusing with conventional lenses. We developed a scheme to detect the presence of the plasma, based on its screening property. Using this scheme, we detected plasma channels longer than 1 m and 3.5 m generated by 8 mJ and 90 mJ Input Pulse energies, respectively. Our simulations show that axicon focusing can yield self-guided propagation with or without contribution of plasma, depending on the Input Pulse power.
Masataka Nakazawa - One of the best experts on this subject based on the ideXlab platform.
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Wavelength‐dependent amplification characteristics of femtosecond erbium‐doped optical fiber amplifiers
Applied Physics Letters, 1991Co-Authors: Kenji Kurokawa, Masataka NakazawaAbstract:Amplification characteristics of erbium‐doped optical fiber amplifier have been investigated using femtosecond soliton Pulses with various wavelengths. Soliton trapping is not observed for 210 fs Input Pulses at 1.535 μm but the soliton self‐frequency shift occurs along with the Pulse‐width narrowing. When the Input Pulse width is 470 fs, the soliton Pulse is amplified by the optical gain at 1.535 μm, where the gain bandwidth is broader than the bandwidth of the Input Pulse. Amplification characteristics at other nonresonant wavelengths are also investigated using a femtosecond soliton Pulse.
B S Yilbas - One of the best experts on this subject based on the ideXlab platform.
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The closed form solutions for Cattaneo and stress equations due to step Input Pulse heating
Physica B: Condensed Matter, 2010Co-Authors: Hussain Al-qahtani, B S YilbasAbstract:The analytical solution for the temperature and stress fields in a solid subjected to a step Input Pulse heating is presented. The closed form solutions of Cattaneo and thermal stress equations are obtained using the Laplace transformation technique. The predictions obtained from the closed form solutions are presented in nondimensional form. It is found that temperature rise is rapid in the early heating period and as the time progresses, temperature rise becomes gradual. The stress generated in the heating cycle is tensile while it becomes compressive in the cooling cycle.
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thermal stress development due to laser step Input Pulse heating
Journal of Thermal Stresses, 2006Co-Authors: B S Yilbas, N AgeeliAbstract:The closed form solution for the thermal stress distribution inside the substrate material is obtained for a stress-free boundary condition at the surface, which is the most practical situation in laser material processing. Since the molecules in the liquid and gas phases are free to move, the thermal strains in these phases are significantly small, so that the thermal stress field is formulated for the solid phase and the heat conduction equation for solid heating, therefore, considered only. It is found that the temperature in the region next to the surface vicinity drops sharply while the temperature reduces gradually in the surface vicinity due to the high amount of energy absorption from the irradiated field in this region. The variation in the temperature gradient in the surface region results in thermal stress waves propagating into the substrate material at a constant speed. Thermal stress below the surface is compressive due to high thermal strain developing in this region.
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Entropy generation due to laser step Input Pulse heating
Heat and Mass Transfer, 2004Co-Authors: B S YilbasAbstract:Laser heating of surfaces results in thermal expansion of the substrate material in the region irradiated by a laser beam. In this case, the thermodynamic irreversibility associated with the thermal process is involved with temperature and thermal stress fields. In the present study, entropy analysis is carried out to quantify the thermodynamic irreversibility pertinent to laser Pulse heating process. The formulation of entropy generation due to temperature and stress fields is presented and entropy generation is simulated for steel substrate. It is found that the rapid rise of surface displacement in the early heating period results in high rate of entropy generation due to stress field in the surface region while entropy generation due to temperature field increases steadily with increasing depth from the surface.
J M Dudley - One of the best experts on this subject based on the ideXlab platform.
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Route to Coherent Supercontinuum Generation in the Long Pulse Regime
IEEE LEOS Winter Topicals Meeting Series, 2009Co-Authors: G. Genty, J M DudleyAbstract:We study numerically the possibility of generating supercontinuum with improved stability characteristics through modulation of the Input Pulse. General guidelines for the choice of modulation parameters leading to coherent supercontinuum generation in the long Pulse regime are given.
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Modulation control and spectral shaping of supercontinuum generation in the picosecond regime
2008Co-Authors: G. Genty, J M Dudley, B. EggletonAbstract:We numerically study the shaping of broadband supercontinuum spectra through the use of strong Input Pulse modulation. The underlying physical mechanism is shown to be rogue wave control through induced modulation instability.
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Chirp-controlled soliton fission in tapered optical fibers
Applied Physics B - Laser and Optics, 2006Co-Authors: D. Turke, J M Dudley, W. Wohlleben, J. Teipel, M. Motzkus, B. Kibler, H. GiessenAbstract:Manipulation of the Input Pulse chirp during supercontinuum generation in tapered fibers provides precise control of the soliton fission process taking place in the taper waist. Simulations and experiments demonstrate that controlling this pre-chirp by a Pulse shaper can be applied to compensate for deleterious effects due to untapered fiber pigtails. Temporal and cross-correlation frequency resolved measurements are utilized to show, that the control of the soliton fission dynamics can be obtained by manipulating the Input Pulse chirp through the imposition of a quadratic spectral phase.
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Fundamental amplitude noise limitations to supercontinuum spectra generated in a microstructured fiber
Applied Physics B: Lasers and Optics, 2003Co-Authors: Kristan L Corwin, Nathan R Newbury, J M Dudley, Stephane Coen, Scott A Diddams, Brian R Washburn, K Weber, R S WindelerAbstract:Broadband supercontinuum spectra are generated in a microstructured fiber using femtosecond laser Pulses. Noise properties of these spectra are studied through experiments and numerical simulations based on a generalized stochastic nonlinear Schrödinger equation. In particular, the relative intensity noise as a function of wavelength across the supercontinuum is measured over a wide range of Input Pulse parameters, and experimental results and simulations are shown to be in good quantitative agreement. For certain Input Pulse parameters, amplitude fluctuations as large as 50% are observed. The simulations clarify that the intensity noise on the supercontinuum arises from the amplification of two noise Inputs during propagation - quantum-limited shot noise on the Input Pulse, and spontaneous Raman scattering in the fiber. The amplification factor is a sensitive function of the Input Pulse parameters. Short Input Pulses are critical for the generation of very broad supercontinua with low noise.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
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fundamental amplitude noise limitations to supercontinuum spectra generated in a microstructured fiber
Applied Physics B, 2003Co-Authors: Kristan L Corwin, Nathan R Newbury, J M Dudley, Stephane Coen, Scott A Diddams, Brian R Washburn, K Weber, R S WindelerAbstract:Broadband supercontinuum spectra are generated in a microstructured fiber using femtosecond laser Pulses. Noise properties of these spectra are studied through experiments and numerical simulations based on a generalized stochastic nonlinear Schrodinger equation. In particular, the relative intensity noise as a function of wavelength across the supercontinuum is measured over a wide range of Input Pulse parameters, and experimental results and simulations are shown to be in good quantitative agreement. For certain Input Pulse parameters, amplitude fluctuations as large as 50% are observed. The simulations clarify that the intensity noise on the supercontinuum arises from the amplification of two noise Inputs during propagation – quantum-limited shot noise on the Input Pulse, and spontaneous Raman scattering in the fiber. The amplification factor is a sensitive function of the Input Pulse parameters. Short Input Pulses are critical for the generation of very broad supercontinua with low noise.