  We apply spinning-disc picometrology to measure the complex refractive index
of graphene on thermal oxide on silicon. The refractive index varies from n =
2.4-1.0i at 532 nm to n = 3.0-1.4i at 633 nm at room temperature. The
dispersion is five times stronger than bulk graphite (2.67-1.34i to 2.73-1.42i
from 532 nm to 633 nm).
