Observation of a Long-Wavelength Hosing Modulation of a High-Intensity Laser Pulse in Underdense Plasma

TL;DR

This paper reports the first experimental detection of a long-wavelength hosing modulation in high-intensity laser pulses propagating through underdense plasma, revealing a new dynamic behavior influenced by plasma density and laser focus asymmetries.

Contribution

It provides the first experimental observation and analysis of long-wavelength laser hosing in underdense plasma, linking it to focus asymmetries and plasma density.

Findings

Hosing wavelength scales as n_e^-3/2

Hosing caused by focus asymmetries

Experimental and simulation results agree

Abstract

We report the first experimental observation of a long-wavelength hosing modulation of a high-intensity laser pulse. Side-view images of the scattered optical radiation at the fundamental wave-length of the laser reveal a transverse oscillation of the laser pulse during its propagation through underdense plasma. The wavelength of the oscillation \lambda_hosing depends on the background plasma density n_e and scales as \lambda_hosing~n_e^-3/2. Comparisons with an analytical model and 2-dimensional particle-in-cell simulations reveal that this laser hosing can be induced by a spatio-temporal asymmetry of the intensity distribution in the laser focus which can be caused by a misalignment of the parabolic focussing mirror or of the diffraction gratings in the pulse compressor.