  We demonstrate a nanotip electron source based on a graded index multimode
silica optical fiber, tapered at one end to a radius of curvature r ~ 50 nm and
coated with a thin film of gold. We report observation of laser-induced
electron photoemission at tip bias potentials below the onset of dark field
emission (FE). Single-photon photofield emission (PFE) is identified as the
emission mechanism, which exhibits fast switching times with an upper limit on
the order of 1 {\mu}s. The explored fiber optic nanotips are flexible
back-illuminated emitters, which can be operated in continuous wave (CW) and
pulsed modes using lasers with photon energies in the visible range or higher.
The mechanical flexibility of the source can facilitate externally controlled
positioning. Multiple, individually addressable, nanotips may be assembled into
a bundle for applications such as computational electron ghost imaging.
