Tunable terahertz frequency comb generation using time-dependent graphene sheets

We investigate the interaction between electromagnetic pulses and two-dimensional current sheets whose conductivity is controlled as a function of time by the generation of photocarriers, and we discuss its applicability to tunable frequency comb generation. To this aim, we develop an analytical model that permits the calculation of the scattered waves off a thin sheet with time-dependent, dispersive sheet conductivity. We evaluate the transmitted spectrum as a function of the dispersive behavior and the modulation frequency of the number of photocarriers. We conclude that such active materials, e.g., time-dependent graphene sheets, open up the possibility to manipulate the frequency of incident pulses and, hence, could lead to highly tunable, miniaturized frequency comb generation.