Surface Plasmon Polaritonic Crystals for Applications in Optical communications

The integration and reduction in the photonic device sizes are essential for the development of applications in short-range interconnects and optical signal processing. Surface plasmon polaritonic crystals (SPPCs) can allow the manipulation of optical information in the microscale level, by coupling photons with collective electron oscillations at a metal–dielectric interface. This thesis investigates, both numerically and experimentally, the excitation and propagation of the surface plasmon polaritonic (SPP) modes on finite-size SPPCs, their dependence on the nanostructured geometry and the potential applications in implementing different device functions including SPP-beam shaping, such as focusing and splitting, and wavelength/polarisation demultiplexing. By controlling the SPPC geometry and the excitation beam parameters, directional control of propagating plasmonic modes properties, such as the beam direction, focusing power and beam width, can be achieved. The wavelength-dependent SPP signal spatial separation, due to coupling to the several eigenmodes, and the reduction of the cross-talk by combining polarisation and wavelength modulation have also been shown. In addition, a compact 4-level polarisation discriminator based on a planar, microscale-scale SPPC was developed as part of the research. Its capability to spatially separate linearly polarised signals with azimuth angles 0o , 45o , 90o and 135o , and define the S1 and S2 stokes parameters of any elliptical polarisation state was demonstrated and experimentally tested. The concept was extended to propose a fibre-coupled polarimeter, able to identify the three Stokes vectors parameters, based on the combination of the SPPC with a high -birefringence fibre. The use of SPPCs for the implementation and miniaturisation of key optical communication functionalities, in-plane plasmonic beam manipulation and polarisation/wavelength dependent SPP beam propagation, demonstrated in this work can be important for the development of novel integrated nanophotonic functionalities for subwavelength management of optical signals and the design of a new family of compact devices for optical communication applications