Spatio-temporal sampling of near-petahertz vortex fields

TL;DR

This paper presents a novel near-field sampling technique for high-resolution measurement of ultrafast visible light fields, enabling detailed spatio-temporal and polarization-resolved characterization of complex optical fields.

Contribution

The authors introduce a nanometric needle tip-based near-field method that overcomes traditional resolution limits and captures the full vectorial and temporal evolution of petahertz optical fields.

Findings

Resolved the spiral wave-front of femtosecond light pulses with OAM.

Achieved reliable characterization of near-petahertz fields.

Demonstrated polarization-sensitive field reconstruction.

Abstract

Measuring the field of visible light with high spatial resolution has been challenging, as many established methods only detect a focus-averaged signal. Here, we introduce a near-field method for optical field sampling that overcomes that limitation by employing the localization of the enhanced near-field of a nanometric needle tip. A probe field perturbs the photoemission from the tip, which is induced by a pump pulse, generating a field-dependent current modulation that can easily be captured with our electronic detection scheme. The approach provides reliable characterization of near-petahertz fields. We show that not only the spiral wave-front of visible femtosecond light pulses carrying orbital angular momentum (OAM) can be resolved, but also the field evolution with time in the focal plane. Additionally, our method is polarization sensitive, which makes it applicable to vectorial field reconstruction.