Enhanced nonlinearities in epsilon-near-zero transparent conductive oxides for applications in nanophotonics

Abstract

Plasmonic brings the promise to overcome both the speed limitation of electronics and the scalability issue of photonics, however it is affected by fundamental issues such as large ohmic losses, lack of tunability and CMOS compatibility. All these problems prevent a widespread of plasmonic technologies. My research focuses on developing a new class of plasmonic devices based on Transparent Conductive Oxides (TCOs). Because of their low losses in the NIR, their fabrication flexibility, and exceptional optical nonlinearities, TCOs could drastically mitigate all the previously listed limitations. Great part of the thesis deals with the characterization of Aluminium Zinc Oxide (AZO) and Gallium Zinc Oxide (GZO) in the linear and nonlinear regime within the ENZ spectral region, by using various alterations of a standard pump and probe set-up. My work shows how large and ultra-fast nonlinearities, triggered by both interband and intraband excitations, are combined to produce independent and algebraically summable nonlinear effects in TCOs and how degenerate optical excitation can lead to an unprecedented enhancement of the nonlinear Kerr effect. In the direction of low power frequency conversion, experiments of semi-degenerate four-wave mixing have also been performed. Finally, ultra-fast tunable nanocavities based on a Gallium Zinc Oxide (GZO) are also reported.