  Electronic nematicity have attracted a great deal of interest in the
unconventional superconductivity research. We present an experimental method to
investigate reflectivity anisotropy by the electronic nematicity and its
non-equilibrium dynamics. Our experimental results on
Ba(Fe$_{0.955}$Co$_{0.045}$)$_{2}$As$_{2}$ single crystal clearly feature the
broken four-fold symmetry along directions parallel to Fe-Fe bonding. Numerical
simulations using WVASE from Woollam Co. demonstrate that our method is highly
reliable under various experimental conditions. Finally, we perform
time-resolved reflectivity anisotropy measurement confirming that
photo-excitation by 1.55 eV photons suppresses the reflectivity anisotropy due
to nematic order.
