Nonlinear optical absorption in graphene via two-photon absorption process

Nonlinear optical absorption phenomena in monolayer graphene for scattering between carriers and K-optical phonons are studied via investigating the phonon-assisted cyclotron resonance (PACR) effect. The positions of the PACR peaks are indicated. Only principal transitions make a significant contribution to the optical absorption power. We found that with the increase of the magnetic field, the optical absorption spectrum increases in magnitude and also gives the blue-shift in both one- and two-photon absorption processes. Besides, the half-width is found to be almost independent from the change of temperature, but proportional to the square root of magnetic field, and this agrees with the previous experimental observations.