  The IceCube Neutrino Observatory is the world's largest neutrino detector
with a cubic-kilometer instrumented volume at the South Pole. It is preparing
for a major upgrade that will significantly increase its sensitivity. A
promising technological innovation investigated for this upgrade is wavelength
shifting optics. Augmenting sensors with such optics could increase the
photo-collection area of IceCube's digital optical modules, and shift the
incoming photons' wavelength to where these modules are the most sensitive.
Here we investigate the use of IceCube's drill holes themselves as wavelength
shifting optics. We calculate the sensitivity enhancement due to increasing the
ice's refractive index in the holes, and infusing wavelength-shifting substrate
into the ice. We find that, with adequate wavelength-shifter infusion, every
~0.05 increase in the ice's refractive index will increase IceCube's photon
sensitivity by 100%, opening the possibility for the substantial, cost
effective expansion of IceCube's reach.
