  The Keck Planet Imager and Characterizer (KPIC) is an upgrade to the Keck II
adaptive optics system that includes an active fiber injection unit (FIU) for
efficiently routing light from exoplanets to NIRSPEC, a high-resolution
spectrograph. Towards the end of 2019, we will add a suite of new coronagraph
modes as well as a high-order deformable mirror. One of these modes, operating
in $K$-band (2.2$\mu m$), will be the first vortex fiber nuller to go on sky.
Vortex Fiber Nulling (VFN) is a new interferometric method for suppressing
starlight in order to spectroscopically characterize exoplanets at angular
separations that are inaccessible with conventional coronagraph systems. A
monochromatic starlight suppression of $6\times10^{-5}$ in 635 nm laser light
has already been demonstrated on a VFN testbed in the lab. A polychromatic
experiment is now underway and coupling efficiencies of $<5\times10^{-4}$ and
$\sim5\%$ have been demonstrated for the star and planet respectively in 10%
bandwidth light. Here we describe those experiments, the new KPIC VFN mode, and
the expected performance of this mode using realistic parameters determined
from on-sky tests done during the KPIC commissioning.
