Abstract
Laser filamentation is responsible for the deposition of a significant part of the laser pulse energy in the propagation medium. We found that using terawatt laser pulses and moderately strong focusing conditions in air, more than 60 % of the pulses energy is transferred to the medium, eventually degrading into heat. This results in a strong hydrodynamic reaction of air with the generation of shock waves and associated underdense channels for each of the generated multiple filaments. In the focal zone, where filaments are close to each other, these discrete channels eventually merge to form a single cylindrical low-density tube over a ~ 1 µs timescale. We measured the maximum lineic deposited energy to be more than 1 J·m-1.
Highlights
Laser filamentation is a propagation regime for ultrashort laser pulses in transparent media reached when their peak power exceeds a critical power Pcr, which is about 5 GW in air at a wavelength of 800 nm
As the efficiency of these structures is strongly dependent on the amplitude of laser-induced hydrodynamics effects, that is on local deposited energy, it is crucial to be able to increase the density of deposited energy at the required level
We find that using the shortest and most energetic laser pulse with a moderately strong focusing, more than 60 % of the laser pulse energy is converted into heat at the terawatt peak power level
Summary
Laser filamentation is a propagation regime for ultrashort laser pulses in transparent media reached when their peak power exceeds a critical power Pcr, which is about 5 GW in air at a wavelength of 800 nm It results from a complex interplay between the optical Kerr effect, nonlinear energy absorption due to multiphoton and tunnel ionization and plasma defocusing [1]. Investigating the air hydrodynamics response by means of transverse interferometry, we witnessed a spontaneous evolution of the system from discrete underdense channels to a cylindrically-symmetric form with a single, large channel and an associated unique shock wave, partially negating the deleterious effect of multifilamentation In optimal conditions, this channel lasts for more than 100 ms. Using a sonographic technique [15, 16], we estimated the peak lineic deposited energy to be 1.3 J · m−1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
