Femtosecond streaking in ambient air

TL;DR

This paper introduces a new method for measuring the temporal evolution of electric fields in ambient air using femtosecond laser pulses, enabling real-time waveform visualization similar to radio signals.

Contribution

The novel technique detects transient currents in air plasma to directly measure electric field waveforms in ambient conditions, unlike previous methods requiring specialized environments.

Findings

Successfully measures electric field waveforms in ambient air.

Validates method against existing laser-pulse characterization techniques.

Allows real-time visualization of electric fields on an oscilloscope.

Abstract

We demonstrate a novel method to measure the temporal evolution of electric fields with optical frequencies. Our technique is based on the detection of transient currents in air plasma. These directional currents result from sub-cycle ionization of air with a short pump pulse, and the steering of the released electrons with the pulse to be sampled. We assess the validity of our approach by comparing it with different state-of-the-art laser-pulse characterization techniques. Notably, our method works in ambient air and facilitates a direct measurement of the field waveform, which can be viewed in real time on an oscilloscope in the exact same way as a radio frequency signal.