  We address the optical conductivity of undoped bilayer graphene in the
presence of a finite bias voltage at finite temperature. The effects of gap
parameter and stacking type on optical conductivity are discussed in the
context of tight binding model Hamiltonian.
  Green's function approach has been implemented to find the behavior of
optical conductivity of bilayer graphene within linear response theory. We have
found the frequency dependence of optical conductivity for different values of
gap parameter and bias voltage. Also the dependence of optical conductivity on
the temperature has been investigated in details. A peak appears in the plot of
optical conductivity versus frequency for different values of temperatures and
bias voltage.
  Furthermore we find the frequency position of broad peak in optical
conductivity goes to higher values with increase of gap parameter for both
bernal and simple stacked bilayer graphenes.
