Graphene, two-dimensional material comprised of carbon atoms, has attracted great interest in optical devices owing to outstanding electrical and optical properties such as high thermal conductivity, outstanding electrical mobility, flexible, and exceptional mechanical strength. Above all, since the complex permittivity of graphene is easily tunable, it is considered as a promising material for wavelength tunable photonic devices. In spite of the superb properties, graphene-based photonic device applications have been limited by the low light-graphene interaction. In this dissertation, author presents several solutions to mitigate the restriction by using unique properties of graphene. In particular, author designed highly efficient optical modulators by using epsilon-near-zero (ENZ) mode that extremely confines light in a graphene layer: a free space-type graphene-based modulator using surface plasmon resonance and a waveguide-type modulator inserting a graphene layer into a Si waveguide. The designed modulators provide higher modulation depths and lower insertion losses compared with previously reported graphene-based modulators. Author also realized perfect absorption by using graphene ENZ mode in a modified Otto configuration. The wavelength of the perfect absorption is tunable and the perfect absorption can be achieved regardless of graphene quality. Plasmon-induced transparency (PIT) in coupled graphene grating has also been demonstrated. The wavelength tenability of the PIT peak and its modulator application in mid-infrared has been investigated.
The theoretical analysis of the proposed photonics devices has been conducted by using various numerical tools, including the finite element method (FEM), the using rigorous coupled wave method (RCWA), and the transfer matrix method (TMM), as well as by using a Maxwell’s equation solver developed by the author. The FEM and the Maxwell’s equation solver were used for the modal analysis of the proposed structures. The RCWA and the TMM were used for the calculation of the transmission, reflection, and absorption spectra of the proposed structures.
