  Despite the fundamental nature of the edge state in topological physics,
direct measurement of electronic and optical properties of the Fermi arcs of
topological semimetals has posed a significant experimental challenge, as their
response is often overwhelmed by the metallic bulk. However, laser-driven
currents carried by surface and bulk states can propagate in different
directions in nonsymmorphic crystals, allowing for the two components to be
easily separated. Motivated by a recent theoretical prediction \cite{chang20},
we have measured the linear and circular photogalvanic effect currents deriving
from the Fermi arcs of the nonsymmorphic, chiral Weyl semimetal RhSi over the
$0.45 - 1.1$ eV incident photon energy range. Our data are in good agreement
with the predicted magnitude of the circular photogalvanic effect as a function
of photon energy, although the direction of the surface photocurrent departed
from the theoretical expectation over the energy range studied. Surface
currents arising from the linear photogalvanic effect were observed as well,
with the unexpected result that only two of the six allowed tensor element were
required to describe the measurements, suggesting an approximate emergent
mirror symmetry inconsistent with the space group of the crystal.
