Mr Justus Bohn
The resonant responses of surface plasmon-polaritons form the basis for most metamaterial designs. However, many proposed applications of metamaterials suffer greatly from damping caused by absorption in the metals. Over the years, several proposals to compensate loss by incorporating active gain media into plasmonic systems have been made [Nature Photonics 4, 382 (2010)]. However, in practice, it is often difficult to overlap the mode volume with the gain material, an effect that typically leads to very small values for gain (~0.001%) in experiment [Phys. Rev. Lett. 94, 177401 (2005)].
Meanwhile, zero (or narrow) gap materials such as graphene, due to the continuous nature of their bands, can provide broadband gain [Science 351, 246 (2016)]. Moreover, such 2D materials can also be plasmonic. Very recently, it has been pointed out that this, in principle, allows for a highly unusual situation: when optically pumped, it is possible for such materials to exhibit gain and plasmonic responses simultaneously [Phys. Rev. B 91, 075404 (2016), Phys. Rev. B 93, 041408(R) (2016)]. Such a system, where plasmon losses could be completely compensated by optically pumping the material would be highly advantageous, completely removing the critical requirement of mode overlap. In this PhD project, we will look to investigate and harness this gain effect in a series of proof-of-principle experiments.