  The optical conductivity of graphene strained uniaxially is studied within
the Kubo-Greenwood formalism. Focusing on inter-band absorption, we analyze and
quantify the breakdown of universal transparency in the visible region of the
spectrum, and analytically characterize the transparency as a function of
strain and polarization. Measuring transmittance as a function of incident
polarization directly reflects the magnitude and direction of strain. Moreover,
direction-dependent selection rules permit identification of the lattice
orientation by monitoring the van-Hove transitions. These photoelastic effects
in graphene can be explored towards atomically thin, broadband optical
elements.
