Optical conductance and transmission in bilayer graphene

Abstract

We present a theoretical study of the optoelectronic properties of bilayer graphene. The optical conductance and transmission coefficient are calculated using the energy-balance equation derived from a Boltzmann equation for an air/graphene/dielectric-wafer system. For short wavelengths (λ<0.2 μm), we obtain the universal optical conductance σ=e2/(2ℏ). Interestingly, there exists an optical absorption window in the wavelength range 10–100 μm, which is induced by different transition energies required for inter- and intra-band optical absorptions in the presence of the Moss–Burstein effect. As a result, the position and width of this absorption window depend sensitively on temperature, carrier density, and sample mobility of the system. These results are relevant for applications of recently developed graphene devices in advanced optoelectronics such as the infrared photodetectors.