Generation of long-lived underdense channels using femtosecond filamentation in air

TL;DR

This study investigates the formation and longevity of underdense air channels created by femtosecond laser filamentation, revealing channels lasting over 90 ms and linking experimental parameters to filamentation dynamics.

Contribution

It provides detailed characterization of long-lived underdense channels in air generated by femtosecond filamentation and compares experimental results with hydrodynamic simulations.

Findings

Underdense channels last over 90 ms.

Shock waves are generated under tight focusing conditions.

Simulation results agree well with experimental measurements.

Abstract

Using femtosecond laser pulses at 800 and 400 nm, we characterize the formation of underdense channels in air generated by laser filamentation at the millijoule energy level by means of transverse interferometry. We find that using tight focusing conditions, filamentation generates a shock wave and that the resulting low-density channel lasts for more than 90 ms. Comparison of these results with hydrodynamic simulations using an Eulerian hydrodynamic code gives an good agreement and allows us to estimate the initial gas peak temperature at $\sim$ 1000 K. The influence of experimental parameters such as the focusing conditions for the ultrashort laser pulse, its polarization or the wavelength is studied and linked to previous characterizations of filamentation-generated plasma columns.