Nanoplasmonic surface structures for integrated photonics

Abstract

Nanoplasmonic surfaces are known to be able to alter the localisation and propagation characteristics of light owing to the subwavelength interactions with the metallic elements. The recent improvements of nanolithography and self-assembly techniques have enabled the design of ever smaller and intricate structures with a high precision, allowing for research into more complex nanoplasmonic structures that control light on the nano-scale. Up until now, plasmonic surfaces are mostly operated with out-of-plane excitation which, although well-established and experimentally convenient to perform, has limited potential for on-chip applications. The integration of surface plasmonic structures with photonic waveguides allows for light to be con ned to a guiding layer while being kept in interaction along the surface structure without inducing uncontrolled scattering or excessive dissipative loss. In this work, plasmonic surface structures such as plasmonic antennas and array structures that are integrated with a CMOS compatible platform are explored. In particular, a new class of plasmonic surfaces, plasmonic nanogap tilings, are introduced. Remarkably, these simple periodic structures provide a rich physics characterised by many di erent regimes of operation, including subwavelength surface enhancement, hybrid plasmonic-photonic resonances, transmission stop-bands, resonant back scattering, coupling to out-ofplane radiation and asymmetric transmission. The ability of the nanogap tiling to concentrate the eld on the surface is studied in detail as it allows for sensing changes in the dielectric medium on the accessible surface or the inclusion of nonlinear or gain materials to functionalise the device in an integrated setup.