Intrinsic VHE Gamma-ray spectra of Blazars as a probe for Extragalactic
  Background Light
  Very high energy (VHE) $\gamma$-rays above 10$'$s of GeV energy, emitted from
distant blazars, are attenuated by photons from the extragalactic background
light (EBL). Unfortunately, neither the EBL nor the intrinsic blazar spectrum
is accurately known to derive one quantity from the other. In this work we use
a homogeneous one zone model involving synchrotron, synchrotron self Compton
(SSC) and external Compton (EC) emission mechanisms to estimate the intrinsic
VHE spectra of blazars. The model is applied on three VHE blazars, namely
PKS2155-304, RGB J0710+591 and 3C279, for which simultaneous multi-wavelength
data are available from various observations. The predicted values of the
intrinsic VHE fluxes are then compared with the observations by imaging
atmospheric Cherenkov telescopes to determine the optical depth of VHE
$\gamma$-rays. On comparing these optical depth values with those predicted by
four different EBL models, we observe a somewhat pronounced systematic
deviation for PKS2155-304 and 3C279 at higher energies, especially for the EBL
model proposed by Finke et al.(2010). We attribute this deviation to be an
outcome of either the failure of the extrapolation of blazar SED to VHE
energies and/or due to various assumptions buried in the EBL models.
