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ItemOptical nano-antennas( 2015)Wavelength division multiplexing/demultiplexing in radio frequency communication networks and fibre-optic networks requires sophisticated hardware. One of the challenges in designing subwavelength optical networks is the simplification of the design. When considering the size reduction and feasibility, a design based on fewer constituent elements is highly desirable. Ultra-compact wavelength multiplexers/demultiplexers will play a vital role in all-optical communication networks of the future. The challenge is to use the simplest and fewest antenna elements to achieve a functionality as sophisticated as a wavelength demultiplexer. How a pair of metallic nano-rods with different lengths can achieve such complex functionality is investigate both numerically and analytically. The study is extended to a single asymmetric cross-shaped nanoparticle. Holes perforated in metallic films are considered as slot antennas and are of particular interest in the design of miniaturised colour filters, refractive index sensors, biosensors, wave plates and other miniaturised optical elements. As part of this project, two different techniques of fabricating arrays of holes were employed. The quality and accuracy of fabricated arrays using electron ion beam lithography were compared to those fabricated with focused ion beam lithography. In both cases, periodicities of the arrays were fabricated accurately, whereas the aperture dimensions deviated from those intended. Some authors base their designs on resonant localized surface plasmons associated with the shape resonances of the apertures that are highly susceptible to geometrical defects arising during the fabrication. Detuning such shape resonances to achieve a certain phase requirements, therefore, are also prone to fabrication errors. Arrays of circular holes on the other hand are simpler to fabricate with accurate periodicities. A novel approach in designing miniaturised wave plates based purely on the surface plasmon polaritons that depend solely on the detuned periodicities of the array is proposed with simulation agreeing the experiment. A novel technique in converting a hole array (that is supported on a glass substrate) into a free standing array is also applied to the abovementioned wave plate. Experimental results of such array showed the device acts as a highly efficient refractive index sensor as well as a tuneable quarter wave plate. Prior to this, however, a simple analytical model that explains the origin of the peaks and phase relations in the spectral line associated with hole arrays was developed. The optical responses of arrays based on surface plasmon polaritons are highly sensitive to the angle of incidence. Condition for which such arrays become desensitized to the incident angle was investigate and shown that despite claims regarding depolarization observed in hole arrays, it is possible to steadily control their polarization response. Bullseye antennas with symmetric cross-shaped apertures at their centre are investigated and designed for shaping the radiation pattern of the transmitted light in the far-field. Designs were carried out using finite element methods and experimental data agree with those obtained numerically. A bullseye structure with an asymmetric cross-shaped aperture was also modelled, fabricated and characterised. Experimental data confirms that it is possible to control the radiation pattern as well as the polarization state of the transmitted light when tailoring the surface surrounding an asymmetric cross-shaped aperture with concentric circular corrugations. Another benefit of a resonant slot antenna is its ability to interact with a nearby quantum emitter. Strong and highly localized fields confined to the cavity can interact with those of a quantum emitter positioned inside it. In the strong coupling regime, this leads to an increase in the radiated power by the system as a whole. Although the enhancement to the radiative decay rate is not strictly associated with the antenna theory, one can draw an analogy between the antenna’s gain and the increase in the radiated power observed in a plasmonic antenna when integrated with a quantum emitter. Numerical solutions showed a high yield in the scattered power with a highly directional radiation pattern when a nan-diamond is positioned inside a cross-shaped aperture in a bullseye setting. The integration process of such nanoparticles with subwavelength apertures is cumbersome at the present. A novel approach is therefore proposed in coupling the emission of a NV- colour centre to the plasmonic surface modes based on the utilization of diamond substrates. The influence of the film thickness and the substrate’s refractive index on the surface modes at the superstrate is an important study as the interaction between the holes in a slot antenna array is influenced by these modes. The investigation of such effects, however, is not possible in a period array of holes due to the convolution of the surface plasmons with the Bloch waves. Studies of the surface plasmon polaritons launched by an isolated sub-wavelength slit perforating a metallic thin film showed the existence of a non-travelling interference envelope when the thickness of the film becomes comparable to the skin depth.