0000000000495603
AUTHOR
J. Houzet
Interpretation of negative birefringence observed in strong-field optical pump-probe experiments: High-order Kerr and plasma grating effects
The analysis of negative birefringence optically induced in major air components (Loriot et al., [1, 2]) is revisited in light of the recently reported plasma grating-induced phase-shift effect predicted for strong field pump-probe experiments (Wahlstrand and Milchberg, [3]). The nonlinear birefrin- gence induced by a short and intense laser pulse in argon is measured by femtosecond time-resolved polarimetry. The experiments are performed with degenerate colors, where the pump and probe beam share the same spectrum, or with two different colors and non-overlapping spectra. The in- terpretation of the experimental results is substantiated using a numerical 3D+1 model accounting for nonlinear…
Probing ultrafast thermalization with field-free molecular alignment
International audience; The rotation-translation thermalization of CO2 gas is investigated 500 ps after its preheating by a nonresonant short and intense laser pulse. The temperature of thermalization is optically determined with two additional short laser pulses enabling a field-free molecular alignment process and its probing, respectively. The measurements are performed for various intensities of the preheat pulse, leading to the observation of different temperatures which are in very good agreement with classical molecular dynamics simulations. The results can be regarded as a step towards real-time tracking of ultrafast relaxation pathways in molecular motion.
Optical kerr effect in the strong field regime
The optical Kerr response of hydrogen atom submitted to a strong and short near infrared laser pulse excitation is studied by solving the full 3D time-dependent Schro¨dinger equation. The nonlinear polarization evaluated at the driving field frequency is compared to the canonical expression derived from perturbation theory. A discrepancy between the two models is observed at large intensity affecting the nonlinear propagation of short and intense laser pulses.
Observation d'effets Kerr d'ordres élevés (HOKE) dans les gaz
Talk given by O. Faucher; National audience