Transient optics of gold during laser irradiation: From first principles to experiment

Blumenstein, Andreas; Zijlstra, Eeuwe S.; Ivanov, Dmitriy S.; Weber, Sebastian T.; Zier, Tobias; Kleinwort, Frederick; Rethfeld, B.; Ihlemann, J.; Simon, Péter; Garcia, Martín E.

doi:10.1103/physrevb.101.165140

Cited by 23 publications

(19 citation statements)

References 39 publications

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“…[30], ] cold ei is set to 0.129 fs −1 . However, this is at least 1.5 times larger than the value determined by many other experiments with gold [52,62,65] or by fitting the room temperature experimental dielectric function of gold [42,62]. Overall, we find good agreement between experimental data [39] and our model, suggesting that Eq.…”

Section: Figure 3 | (A)supporting

confidence: 72%

“…2. This description of the scattering rate has been used successfully for warm dense gold [30] and also for solid gold excited near the ablation threshold [42].…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Whereas reflection and transmission are the directly measured quantities in experiments, theoretical models usually start with the evaluation of the dielectric function or dynamic conductivity [40], which can be based on ab initio methods [41][42][43][44], quantum statistical approaches [45][46][47], classical simulations [48] or a Drude or Drude-Lorentz model [44,49]. For extreme conditions and ultrashort time scales, the modelling of these properties remains challenging.…”

Section: Introductionmentioning

confidence: 99%

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Optical Properties of Gold After Intense Short-Pulse Excitations

2022

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Intense ultrashort laser pulses can create highly excited matter with extraordinary properties. Experimental and theoretical investigations of these extreme conditions are very complex and usually intertwined. Here, we report on a theoretical approach for the electron scattering rates and the optical properties in gold at elevated temperatures. Our theory is based on the degree of occupancy of the conduction band as well as inputs from ab initio simulations and experimental data. After the electron system has reached a quasi-equilibrium, the occupancy is fully determined by the electron temperature. Thus, our approach covers the important relaxation stage after fast excitations when the two-temperature model can be applied. Being based on the electronic structure of solids, the model is valid for lattice temperatures up to melting but the electron temperature might exceed this limit by far. Our results agree well with recent experimental data for both the collision frequencies and the conductivity of highly excited gold. Scattering of sp-electrons by d-electrons is found to be the dominant damping mechanism at elevated electron temperatures and depends strongly on the number of conduction electrons, hence, revealing the microscopic origin of the conductivity change after heating. The supportive benchmarks with experiments are very valuable as the underlying scattering rates determine a number of other transport, optical and relaxation properties of laser-excited matter.

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Section: Figure 3 | (A)supporting

confidence: 72%

“…2. This description of the scattering rate has been used successfully for warm dense gold [30] and also for solid gold excited near the ablation threshold [42].…”

Section: Theoretical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical Properties of Gold After Intense Short-Pulse Excitations

2022

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“…Later on, however, the relaxation of the laser-induced stresses, generated in the vicinity of the target’s surface as a result of the laser heating, has been determined as a main driving mechanism responsible for the nanostructures growth [ 25 , 26 , 27 ]. The specifics of the final nanostructures shape depend on the material as well as on the laser parameters, the dynamical changes of the reflectivity of the material [ 28 , 29 ], and the geometric parameters of the irradiation pattern.…”

Section: Introductionmentioning

confidence: 99%

Formation of Periodic Nanoridge Patterns by Ultrashort Single Pulse UV Laser Irradiation of Gold

et al. 2020

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A direct comparison of simulation and experimental results of UV laser-induced surface nanostructuring of gold is presented. Theoretical simulations and experiments are performed on an identical spatial scale. The experimental results have been obtained by using a laser wavelength of 248 nm and a pulse length of 1.6 ps. A mask projection setup is applied to generate a spatially periodic intensity profile on a gold surface with a sinusoidal shape and periods of 270 nm, 350 nm, and 500 nm. The formation of structures at the surface upon single pulse irradiation is analyzed by scanning and transmission electron microscopy (SEM and TEM). For the simulations, a hybrid atomistic-continuum model capable of capturing the essential mechanisms responsible for the nanostructuring process is used to model the interaction of the laser pulse with the gold target and the subsequent time evolution of the system. The formation of narrow ridges composed of two colliding side walls is found in the simulation as well as in the experiment and the structures generated as a result of the material processing are categorized depending on the range of applied fluencies and periodicities.

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“…Note that the optical parameters are actually time-dependent, since they depend on the state of electrons and phonons. For example, they vary with temperature [ 68 , 69 , 70 ] or band occupation [ 41 , 42 ]. This was, however, not considered in our simulation.…”

Section: Appendix A1 Heat Capacitiesmentioning

confidence: 99%

Influence of Electronic Non-Equilibrium on Energy Distribution and Dissipation in Aluminum Studied with an Extended Two-Temperature Model

2022

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When an ultrashort laser pulse excites a metal surface, only a few of all the free electrons absorb a photon. The resulting non-equilibrium electron energy distribution thermalizes quickly to a hot Fermi distribution. The further energy dissipation is usually described in the framework of a two-temperature model, considering the phonons of the crystal lattice as a second subsystem. Here, we present an extension of the two-temperature model including the non-equilibrium electrons as a third subsystem. The model was proposed initially by E. Carpene and later improved by G.D. Tsibidis. We introduce further refinements, in particular, a temperature-dependent electron–electron thermalization time and an extended energy interval for the excitation function. We show results comparing the transient energy densities as well as the energy-transfer rates of the original equilibrium two-temperature description and the improved extended two-temperature model, respectively. Looking at the energy distribution of all electrons, we find good agreement in the non-equilibrium distribution of the extended two-temperature model with results from a kinetic description solving full Boltzmann collision integrals. The model provides a convenient tool to trace non-equilibrium electrons at small computational effort. As an example, we determine the dynamics of high-energy electrons observable in photo-electron spectroscopy. The comparison of the calculated spectral densities with experimental results demonstrates the necessity of considering electronic non-equilibrium distributions and electron–electron thermalization processes in time- and energy-resolved analyses.

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Transient optics of gold during laser irradiation: From first principles to experiment

Cited by 23 publications

References 39 publications

Optical Properties of Gold After Intense Short-Pulse Excitations

Optical Properties of Gold After Intense Short-Pulse Excitations

Formation of Periodic Nanoridge Patterns by Ultrashort Single Pulse UV Laser Irradiation of Gold

Influence of Electronic Non-Equilibrium on Energy Distribution and Dissipation in Aluminum Studied with an Extended Two-Temperature Model

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