Attosecond metrology in circular polarization

Abstract

Attosecond metrology with linearly polarized light pulses is the basis of a highly successful research area. An even broader impact can be expected from a generalized metrology that covers two-dimensional polarization states, enabling notably the study of chiroptical phenomena on the electronic time scale. Here, we introduce and demonstrate a comprehensive approach to the generation and complete characterization of elliptically to circularly polarized attosecond pulses. The generation relies on a plug-in device of unprecedented simplicity. For the characterization, we introduce Stokes-parameter and attosecond-resolved reconstruction of optical waveforms (SPARROW), which encodes the attosecond-metrology information into the photoemission angle in the polarization plane and accesses all four Stokes parameters of the attosecond pulses. Our study demonstrates a physically transparent scheme for attosecond metrology with elliptical to fully circular polarizations, applicable to both table-top and accelerator-based light sources, which will unlock studies of chiral molecules, magnetic materials, and novel chiroptical phenomena on the most fundamental time scales.