Terahertz Nonlinear Optics of Graphene: From Saturable Absorption to High-Harmonics Generation

Graphene has long been predicted to show exceptional nonlinear optical properties, especially in the technologically important terahertz (THz) frequency range. Recent experiments demonstrated that this atomically-thin material indeed exhibits possibly the largest nonlinear coefficients of any material known to date. These findings in particular pave ways for practical graphene-based applications in ultrafast electronics and optoelectronics operating at THz rates. Here we report on the advances in the booming field of nonlinear THz optics of graphene, and describe the state-of-the-art understanding of the nature of the nonlinear interaction of electrons in graphene with intense THz fields based on the thermodynamic model of electron transport in graphene. We also provide a comparison between different mechanisms of nonlinear interaction of graphene with light fields in THz, infrared and visible frequency ranges.
We conclude the report with the perspectives for the expected technological applications of graphene based on its extraordinary THz nonlinear properties. This report covers the evolution of the field of THz nonlinear optics of graphene from the very pioneering to the state-of-the-art works. It also serves as a concise overview of the current understanding of THz nonlinear optics of graphene, and as a compact reference for researchers entering the field, as well as for the technology developers.