We unveil the origin of the recently revealed polarization-state changes of polarization-shaped few-cycle pulses induced by free-space beam propagation. Simple rules are formulated to show how the orientation and ellipticity of the instantaneous polarization ellipse of the source and propagated pulses relate to each other. We demonstrate our findings with examples that clearly display the relationships found and highlight their relevance. We show, for example, that pulses often used in high-harmonic generation or attosecond pulse production rotate as a whole during free-space beam propagation or upon focusing. A pulse that may reverse its ellipticity from right-handed to left-handed during propagation is also introduced. It is shown that these effects are independent of the beam size and/or focal length. We also present how these instantaneous polarization-state changes could be noticed in classical measurements of light polarization using polarizers, phase retarders, and time-integrating detectors.
© 2014 Optical Society of America
Coherence and Statistical Optics
Original Manuscript: February 5, 2014
Revised Manuscript: March 25, 2014
Manuscript Accepted: April 9, 2014
Published: May 12, 2014
Balázs Major, Miguel A. Porras, and Zoltán L. Horváth, "Rotation of the polarization direction and reversal of helicity of ultrashort pulsed beams propagating in free space," J. Opt. Soc. Am. A 31, 1200-1205 (2014)