Near Field Spatial Mode Modification of Ultraintense Pulse Through Relativistically Transparent Solid Density Targets using Light with and without Orbital Angular Momentum*

Relativistic Transparency (RT) in laser-matter interactions occurs when light incident on an opaque plasma becomes intense enough to drive electrons at relativistic speeds, dropping the effective electron density of the plasma below critical so that it becomes transparent. RT in solid-density targets using ultraintense light (>10²⁰ W/cm²) is still an active research area, with many studies focusing on the turn-on time of the interaction [1]. A recent pump-probe experiment performed at the Scarlet Laser Facility has measured the turn-on and turn-off time scale as well as relativistic polarization effects [2]. Here we discuss the effects to the spatial mode of a pump-only transmitted beam through ultrathin (<30 nm) solid-density targets made in situ using liquid crystal films at the Scarlet laser facility. The interaction was performed using a traditional TEM00 beam mode as well as an l=1 Laguerre-Gaussian (LG) beam mode at a peak incident intensity of 0.5-1 x 10²¹ W/cm². We describe measurements of the transmitted spatial mode of the TEM00 and LG beams.

[1] Palaniyappan, S., et al. Dynamics of relativistic transparency and optical shuttering in expanding overdense plasma. Nature Phys 8, 762-769 (2012)

[2] Zingale, A. et al. in preparation