Prompt increase of ultrashort laser pulse transmission through thin silver films

Abstract

We study experimentally and numerically the increase in ultrashort laser pulse transmissivity through thin silver films caused by the heating of electrons. Low to moderate energy femtosecond laser pulse transmission measurements through 40–125 nm thickness silver films were carried out. We compare the experimental data with the values of transmitted fraction of energy obtained by solving the equations for the field together with the two-temperature model. The measured values were fitted with sufficient accuracy by varying the electron-electron collision frequency whose exact values are usually poorly known. Since transmissivity experiences more pronounced changes with the increase in temperature compared to reflectivity, we suggest this technique for studying the properties of nonequilibrium metals.

Green wavelength femtosecond laser ablated copper surface

“…Thus, it would highly induce the deeper ablation depth at higher fluence input. Second, according to [20,30], the interband absorption effect would induce more electron transition from d-band above Fermi level. These electrons contribute to the electron-electron scattering frequency and also induce the optical properties to vary.…”

Effects of metal heating on the spectral composition and generation efficiency of terahertz radiation

“…However, for high ν and T e energy spectral density and relative change of generation efficiency can still be studied in the framework of the equations ( 3) and (4). Such an approach may provide decent precision in the situation when electron collision frequency is inherently high, such as in thin granulated films with a grain size of 10-20 nm [26]. Equation (3) ignores the heat transfer along the surface of the metal, which is justified when the incident pulse length is greater than the scale of the z-axis temperature non-uniformity.…”