  Photocurrents play a crucial role in various applications, including light
detection, photovoltaics, and THz radiation generation. Despite the abundance
of methods and materials for converting light into electrical signals, the use
of metals in this context has been relatively limited. Nanostructures
supporting surface plasmons in metals offer precise light manipulation and
induce light-driven electron motion. Through inverse design optimization of a
gold nanostructure, we demonstrate enhanced volumetric, unidirectional,
intense, and ultrafast photocurrents via a magneto-optical process derived from
the inverse Faraday effect. This is achieved through fine-tuning the amplitude,
polarization, and their gradients in the local light field. The virtually
instantaneous process allows dynamic photocurrent modulation by varying optical
pulse duration, potentially yielding nanosources of intense, ultrafast, planar
magnetic fields, and frequency-tunable THz emission. These findings opens
avenues for ultrafast magnetic material manipulation and holds promise for
nanoscale THz spectroscopy.
