CC BY
20LMI-I-11
Modelling of the ultrafast dynamics and surface plasmon properties of silicon upon irradiation with mid-IR femtosecond laser pulses
G. Tsibidis1
1FORTH, Insitute of Electronic Structure and Laser, Heraklion, Greece
We present a theoretical investigation of the yet unexplored ultrafast processes and dynamics of the produced excited carriers upon irradiation of Silicon with femtosecond pulsed lasers in the mid-infrared (mid-IR) spectral region. The evolution of the carrier density and thermal response of the electron-hole and lattice subsystems are analysed for various wavelengths Xl in the range between 2.2 ^m and 3.3 p,m where the influence of two and three-photon absorption mechanisms is explored. The role of induced Kerr effect is highlighted and it manifests a more pronounced influence at smaller wavelengths in the mid-IR range. Elaboration on the conditions that leads to surface plasmon (SP) excitation indicate the formation of weakly bound SP waves on the material surface. The lifetime of the excited SP is shown to rise upon increasing wavelength yielding a larger than the one predicted for higher laser frequencies. Calculation of damage thresholds for various pulse durations Tp show that they rise according to a power law (~) where the increasing rate is determined by the exponent Z(Xl). Investigation of the multi-photon absorption rates and impact ionization contribution at different Tp manifests a lower damage for Xl=2.5 p,m compared to that for Xl=2.2 p,m for long Tp.
References
[1] Petrakakis E., Tsibidis G.D., and Stratakis E., Modelling of the ultrafast dynamics and surface
plasmon properties of silicon upon irradiation with mid-IR femtosecond laser pulses' Physical Review B 99, 195201 (2019).
