Theoretical research of single-photon and two-photon absorption in bilayer graphene

The tight-binding model is employed to describe the band structure of bilayer graphene, obtaining the corresponding eigenvalue and eigenfunction. It is easy to simulate the single-photon absorption (SPA) and two-photon absorption (TPA) coefficient in bilayer graphene theoretically using the second-order perturbation theory of the electron-photon interaction. The TPA which is affected by the incident photon energy and electronic relaxation time is analysed systematically. The results show that the SPA coefficient of bilayer graphene changes sectionally with the wavelength and approximates 2.1×108 m-1 when the wavelength is longer than 3100 nm. The TPA coefficient of bilayer graphene appears a giant resonance absorption peak in the infrared (wavelength is about 3100 nm) region. The results will provide theoretical guidance for the application of bilayer graphene in the field of photonics and optoelectronics.