The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jialing Yang - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast laser-induced thermoelastic behavior in Metal Films
International Journal of Mechanical Sciences, 2010Co-Authors: Yu Xin Sun, Masumi Saka, Jialing YangAbstract:Abstract When a thin Metal film is irradiated by an ultrafast laser, the energy of the laser is first absorbed by electrons and then transferred to the lattice. In addition, a thermoelastic wave is generated due to the thermoelastic coupling effect. An ultrafast thermoelasticity model utilizing the parabolic two-step heat conduction model and the generalized thermoelastic theory was formulated to describe the thermoelastic behavior of a thin Metal film irradiated by a femtosecond laser pulse. The temporal profile of the ultrafast laser was regarded as being non-Gaussian. An analytical–numerical technique based on the Laplace transform was used to solve the governing equations and the time histories of the electron temperature, lattice temperature, displacement and stress in a gold film were analyzed. The influence of the thickness of the film was also analyzed. In addition, the propagation of the stress wave through the film was analyzed.
Jun Zhou - One of the best experts on this subject based on the ideXlab platform.
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an electrohydrodynamics model for non equilibrium electron and phonon transport in Metal Films after ultra short pulse laser heating
European Physical Journal B, 2015Co-Authors: Jun Zhou, Ronggui YangAbstract:The electrons and phonons in Metal Films after ultra-short pulse laser heating are in highly non-equilibrium states not only between the electrons and the phonons but also within the electrons. An electrohydrodynamics model consisting of the balance equations of electron density, energy density of electrons, and energy density of phonons is derived from the coupled non-equilibrium electron and phonon Boltzmann transport equations to study the nonlinear thermal transport by considering the electron density fluctuation and the transient electric current in Metal Films, after ultra-short pulse laser heating. The temperature evolution is calculated by the coupled electron and phonon Boltzmann transport equations, the electrohydrodynamics model derived in this work, and the two-temperature model. Different laser pulse durations, film thicknesses, and laser fluences are considered. We find that the two-temperature model overestimates the electron temperature at the front surface of the film and underestimates the damage threshold when the nonlinear thermal transport of electrons is important. The electrohydrodynamics model proposed in this work could be a more accurate prediction tool to study the non-equilibrium electron and phonon transport process than the two-temperature model and it is much easier to be solved than the Boltzmann transport equations.
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an electrohydrodynamics model for non equilibrium electron and phonon transport in Metal Films after ultra short pulse laser heating
arXiv: Materials Science, 2014Co-Authors: Jun Zhou, Ronggui YangAbstract:The electrons and phonons in Metal Films after ultra-short pulse laser heating are in highly non-equilibrium states not only between the electron sub-system and the phonon sub-system but also within the electron sub-system. An electrohydrodynamics model consisting of the balance equations of electron density, energy density of electrons, and energy density of phonons is derived from the coupled non-equilibrium electron and phonon Boltzmann transport equations to study the nonlinear transport phenomena, such as the electron density fluctuation and the transient electrical current in Metal Films, after ultra-short pulse laser heating. The time-dependent temperature distributions is calculated by the coupled electron and phonon Boltzmann transport equations, the electrohydrodynamics model derived in this work, and the two-temperature model for different laser pulse durations, film thicknesses, and laser fluences. We find that the two-temperature model overestimates the electron temperature at the frontsurface of the film and underestimates the damage threshold when the nonlinear thermal transport of electrons is important. The electrohydrodynamics model proposedin this work could be a more accurate prediction tool to study the non-equilibrium electron phonon transport process than the two-temperature model and it is much easier to be solved than the coupled electron and phonon Boltzmann transport equations.
Leonid V Zhigilei - One of the best experts on this subject based on the ideXlab platform.
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melt dynamics and melt through time in continuous wave laser heating of Metal Films contributions of the recoil vapor pressure and marangoni effects
International Journal of Heat and Mass Transfer, 2017Co-Authors: Alexey Volkov, Leonid V ZhigileiAbstract:Abstract The relative contributions of evaporation and melt expulsion due to the recoil vapor pressure and Marangoni effects to the laser damage and melt dynamics in continuous wave (CW) laser interactions with free-standing aluminum Films are evaluated in two-phase hydrodynamic simulations. In order the establish the dominant damage mechanisms in different irradiation regimes, the results of hydrodynamic simulations are compared with the predictions of several simplified models that only account for a subset of the involved processes. The hydrodynamic simulations performed in the range of film thickness from 0.2 mm to 4 mm and laser spot radius from 0.1 mm to 1 cm reveal only a marginal effect of the Marangoni stresses on the overall picture of melt flow and the melt-through time. The recoil pressure effect, on the contrary, is capable of strongly decreasing the melt-through time in a certain range of laser intensity. At laser intensities below this range the melting process is largely defined by heat transfer in the radial direction, while at laser intensities above this range the thickness of the molten pool and the efficiency of melt expulsion decrease and evaporation becomes the primary mechanism of material removal from the center of the laser spot. The range of laser intensities where the melt-through time is controlled by the recoil pressure effect is not unique and depends on the film thickness. A simple two-phase one-dimensional thermal model of laser melting, where melt expulsion due to the recoil pressure effect is accounted for based on the Bernoulli integral, is developed and found to be capable of accurate prediction of the melt-through time above a certain level of laser intensity. The one-dimensional thermal model captures all qualitative trends revealed in the direct hydrodynamic simulations and can be used as a robust engineering tool for the first-order estimation of the conditions for CW laser damage of Metal Films.
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combined atomistic continuum modeling of short pulse laser melting and disintegration of Metal Films
Physical Review B, 2003Co-Authors: D S Ivanov, Leonid V ZhigileiAbstract:The kinetics and microscopic mechanisms of laser melting and disintegration of thin Ni and Au Films irradiated by a short, from 200 fs to 150 ps, laser pulse are investigated in a coupled atomistic-continuum computational model. The model provides a detailed atomic-level description of fast nonequilibrium processes of laser melting and film disintegration and, at the same time, ensures an adequate description of the laser light absorption by the conduction band electrons, the energy transfer to the lattice due to the electron-phonon coupling, and the fast electron heat conduction in Metals. The interplay of two competing processes, the propagation of the liquid-crystal interfaces (melting fronts) from the external surfaces of the film and homogeneous nucleation and growth of liquid regions inside the crystal, is found to be responsible for melting of Metal Films irradiated by laser pulses at fluences close to the melting threshold. The relative contributions of the homogeneous and heterogeneous melting mechanisms are defined by the laser fluence, pulse duration, and the strength of the electron-phonon coupling. At high laser fluences, significantly exceeding the threshold for the melting onset, a collapse of the crystal structure overheated above the limit of crystal stability takes place simultaneously in the whole overheated region within \ensuremath{\sim}2 ps, skipping the intermediate liquid-crystal coexistence stage. Under conditions of the inertial stress confinement, realized in the case of short $\ensuremath{\tau}l~10\mathrm{ps}$ laser pulses and strong electron-phonon coupling (Ni Films), the dynamics of the relaxation of the laser-induced pressure has a profound effect on the temperature distribution in the irradiated Films as well as on both homogeneous and heterogeneous melting processes. Anisotropic lattice distortions and stress gradients associated with the relaxation of the laser-induced pressure destabilize the crystal lattice, reduce the overheating required for the initiation of homogeneous melting down to $T\ensuremath{\approx}{1.05T}_{m},$ and expand the range of pulse durations for which homogeneous melting is observed in 50 nm Ni Films up to \ensuremath{\sim}150 ps. High tensile stresses generated in the middle of an irradiated film can also lead to the mechanical disintegration of the film.
Anatoly V Zayats - One of the best experts on this subject based on the ideXlab platform.
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Near-field photonics: surface plasmon polaritons and localized surface plasmons
Journal of Optics A: Pure and Applied Optics, 2003Co-Authors: Anatoly V Zayats, Igor I. SmolyaninovAbstract:Surface plasmon polaritons and localized surface plasmons are discussed in the context of photonic applications. Near-field imaging of scattering, reflection, interference and localization of surface polaritons is reviewed, and approaches for the implementation of elements of surface polariton optics are presented. Surface plasmon polaritonic crystals and their role in the determination of optical properties of periodically nanostructured Metal Films are described. Non-linear effects related to surface polaritons and localized surface plasmons allowing control of optical properties of nanostructured Metal Films with light are discussed. Surface plasmon optics opens up numerous possibilities for application of these intrinsically two-dimensional excitations in passive and active devices of all-optical integrated circuits.
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light tunneling via resonant surface plasmon polariton states and the enhanced transmission of periodically nanostructured Metal Films an analytical study
Physical Review B, 2003Co-Authors: S A Darmanyan, Anatoly V ZayatsAbstract:An analytical treatment of optical transmission through periodically nanosructured Metal Films capable of supporting surface-plasmon polaritons is presented. The optical properties of such Metal Films are governed by surface polariton behavior in a periodic surface structure forming a surface polaritonic crystal. Due to different configurations of the electromagnetic field of surface polariton modes, only states of even Brillouin zones are responsible for the optical transmission enhancement at normal incidence. The transmission enhancement is related to photon tunneling via resonant states of surface polariton Bloch modes in which the energy buildup takes place. Surface polariton states of at least one of the film interfaces contribute to the transmission resonance which occurs due to tunnel coupling between photons and surface polaritons on the opposite interfaces. Under double-resonance conditions, resonant tunneling between surface polariton states of both interfaces is achieved, which leads to further enhancement of the transmission efficiency. The double-resonance conditions occur not only in the case of a film in symmetric environment but can also be engineered for a film on a substrate. Light tunneling via surface polariton states can take place directly through a structured Metal film and does not necessarily require holes in a film.
S A Darmanyan - One of the best experts on this subject based on the ideXlab platform.
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light tunneling via resonant surface plasmon polariton states and the enhanced transmission of periodically nanostructured Metal Films an analytical study
Physical Review B, 2003Co-Authors: S A Darmanyan, Anatoly V ZayatsAbstract:An analytical treatment of optical transmission through periodically nanosructured Metal Films capable of supporting surface-plasmon polaritons is presented. The optical properties of such Metal Films are governed by surface polariton behavior in a periodic surface structure forming a surface polaritonic crystal. Due to different configurations of the electromagnetic field of surface polariton modes, only states of even Brillouin zones are responsible for the optical transmission enhancement at normal incidence. The transmission enhancement is related to photon tunneling via resonant states of surface polariton Bloch modes in which the energy buildup takes place. Surface polariton states of at least one of the film interfaces contribute to the transmission resonance which occurs due to tunnel coupling between photons and surface polaritons on the opposite interfaces. Under double-resonance conditions, resonant tunneling between surface polariton states of both interfaces is achieved, which leads to further enhancement of the transmission efficiency. The double-resonance conditions occur not only in the case of a film in symmetric environment but can also be engineered for a film on a substrate. Light tunneling via surface polariton states can take place directly through a structured Metal film and does not necessarily require holes in a film.