Time-resolved measurements of electron density and plasma diameter of 1 kHz femtosecond laser filament in air

The temporal evolutions of electron density and plasma diameter of 1 kHz femtosecond laser filament in air are experimentally investigated by utilizing a pump-probe longitudinal diffraction method. A model based on scalar diffraction theory is proposed to extract the spatial phase shift of the probe pulse from the diffraction patterns by the laser air plasma channel. The hydrodynamic effect on plasma evolution at 1 kHz filament is included and analyzed. The measured initial peak electron density of similar to 10(18) cm(-3) in our experimental conditions decays rapidly by nearly two orders of magnitude within 200 ps. Moreover, the plasma channel size rises from 90 mu m to 120 mu m as the delay time increases. The experimental observation is in agreement with numerical simulation results by solving the rate equations of the charged particles.

Automated summary

The temporal evolutions of electron density and plasma diameter of 1 kHz femtosecond laser filament in air were experimentally investigated. A model based on scalar diffraction theory was proposed to extract the spatial phase shift of the probe pulse from the diffraction patterns by the laser air plasma channel. The experimental observation is in agreement with numerical simulation results by solving the rate equations of the charged particles.