  The measurement of transient optical fields has proven critical to
understanding the dynamical mechanisms underlying ultrafast physical and
chemical phenomena, and is key to realizing higher speeds in electronics and
telecommunications. Complete characterization of optical waveforms, however,
requires an optical oscilloscope capable of resolving the electric field
oscillations with sub-femtosecond resolution and with single-shot operation.
Here, we show that strong-field nonlinear excitation of photocurrents in a
silicon-based image sensor chip can provide the sub-cycle optical gate
necessary to characterize carrier-envelope phase-stable optical waveforms in
the mid-infrared. By mapping the temporal delay between an intense excitation
and weak perturbing pulse onto a transverse spatial coordinate of the image
sensor, we show that the technique allows single-shot measurement of few-cycle
waveforms.
