  Time-domain sampling of arbitrary electric fields with sub-cycle resolution
enables a complete time-frequency analysis of a system's response to
electromagnetic illumination. This provides access to dynamic information that
is not provided by absorption spectra alone, and has recently been shown
through measurements in the infrared that time-domain optical-field sampling
offers significant improvements with regard to molecular sensitivity and limits
of detection compared to traditional spectroscopic methods. Despite the many
scientific and technological motivations, time-domain, optical-field sampling
systems operating in the visible to near-infrared spectral regions are seldom
accessible, requiring large driving pulse energies, and large laser amplifier
systems, bulky apparatuses, and vacuum environments. Here, we demonstrate an
all-on-chip, optoelectronic device capable of sampling arbitrary, low-energy,
near-infrared waveforms under ambient conditions. Our solid-state integrated
detector uses optical-field-driven electron emission from resonant nanoantennas
to achieve petahertz-level switching speeds by generating on-chip attosecond
electron bursts. These bursts are used to probe the electric field of weak
optical transients. We demonstrated our devices by sampling the electric field
of a ~5 fJ, broadband near-infrared ultrafast laser pulse using a ~50 pJ
near-infrared driving pulse. Our sampling measurements recovered the weak
optical transient as well as localized plasmonic dynamics of the emitting
nanoantennas $in~situ$. This field-sampling device--with its compact footprint
and low pulse-energy requirements--offers opportunities in a variety of
applications, including: broadband time-domain spectroscopy in the molecular
fingerprint region, time-domain analysis of nonlinear phenomena, and detailed
studies of strong-field light-matter interactions.
