Focal dynamics of multiple filaments: Microscopic imaging and reconstruction

Abstract

International audienceWe observe the complete dynamics of the propagation of very intense, femtosecond laser pulses in air under tight focusing conditions via direct imaging of the entire interaction zone. The whole life history of the focused pulses is then reconstructed by means of numerical simulations. We show that beam breakup leads to a dual-rate increase in filament numbers with laser power. Linearly and circularly polarized pulses give rise to beam breakup and fusion governed by external focusing conditions. For tight focusing conditions, intensity saturation due to plasma generation and nonlinear losses does not limit the intensity growth, thereby giving access to a new propagation regime featured by an efficient laser energy deposition in fully ionized air and intense 10^15 W/cm^2 pulses at the focus

Generation of High-Density Electrons Based on Plasma Grating Induced Bragg Diffraction in Air

“…4:9 Â 10 14 W=cm 2 , which is at least 1 order of magnitude higher than the intensity clamping limit [12]. This agreed with recent results [27,28]. As shown in Fig.…”

Computational modeling of laser-plasma interactions: Pulse self-modulation and energy transfer between intersecting laser pulses

“…It should be emphasized that the PIC method is not suitable for simulation of the entire beam path but only for the propagation inside the high density plasma channel and the region of the two interacting beams. Nevertheless, as is well known [10,15,16] and as our results suggest (see below) the interactions leading to the aforementioned phenomena are limited to these regions, allowing us to obtain an understanding of these processes by PIC simulations.…”

“…At higher pulse intensities, almost complete ionization of the air occurs at the very leading edge of the pulse. The intensity saturation due to plasma generation and nonlinear losses does not limit the intensity growth, leading to a different filamentation process [1] with high density plasma channel and peak intensity exceeding the clamping intensity by a few orders of magnitude [9,10]. This high intensity regime can be achieved by using high energy pulses as well as by tight focusing of relatively modest energy laser beams.…”

Energy deposition from focused terawatt laser pulses in air undergoing multifilamentation

“…where U O2 ≈ 12 eV is the ionization potential of O 2 , z max the position along the multifilament bundle where the peak lineic energy deposition is reached and r 0 the HWHM of the electron density profile. Peak electron density in the case of single filaments generated using a ∼ f /30 focusing has been recorded [23] and numerically estimated [24] to be on the order of 3 × 10 23 m −3 .…”