Laser setup
Schematic of the laser setup consisting of two equal handed, circularly polarized, counterpropagating laser pulses with equal intensities. Electric and magnetic fields are parallel, point along the arrows, rotate in space along the propagation axis, and vary sinusoidal in time and 90° out of phase (image credit: N Milosevic et al. 2004 Phys. Rev. Lett. 92 013002)