Plasmonics in graphene has recently received wide attention in the optics community. This is because the bound electromagnetic modes (plasmons) are tightly confined to the surface and can also be tuned with carrier concentration. Interestingly, with a doping of the order of 1012- 1013 cm-2 that can be achieved with external gates, the plasmon resonance in graphene appears in the infrared (IR) and terahertz (THz) range.
In this talk, I will explore the key question - how does graphene absorption and hence any THz plasmon resonance in graphene evolve with doping, type of carriers and spatial distribution of carriers induced by the external gate ? An understanding of the physical mechanism, correlating the spectra with the type and spatial distribution of charge carriers is necessary and fundamental to the development of THz optical elements using graphene .
I will then describe how the gate tunability of transmission through graphene can be applied to develop THz modulators. For example, we can indirectly modulate the THz beam emitted from a quantum cascade laser, which is a compact, unipolar electrically driven source of THz radiation .
While graphene holds promise for most THz optical elements such as filters, modulators and detectors, there is still a need to realize a compact room temperature THz source for an integrated THz optical system. I will finally describe how nanostructuring quantum cascade lasers might hold an answer to this question.