Applications and practical considerations of polarisation structuring by a Fresnel cone

The polarisation property of light has been known about for hundreds of years. Often its use in technology has been limited to uniform states, however, more recently light with structured polarisation has gained interest. This is largely prompted by availability of spatial light modulators for generation, and increased computation speed to model complex focal fields. My PhD research has extended upon work carried out during a master’s project where we investigated the use of a solid glass cone (so-called Fresnel cone) for generating vector vortex beams. The aim of this thesis is to report on the potential use of a Fresnel cone in microscopy and polarimetry applications, and practical implications discovered. Expanding on the previous work, enhanced fidelity polarisation states are measured and a newly developed Fresnel cone coupling technique is shown, allowing high-efficiency annular vector vortex beam generation. We demonstrate through simulations based on vector diffraction theory that azimuthally polarised light with OAM generated using a Fresnel cone can provide sub-diffraction limited focal spots, below those of more well-known radially polarised light. Practical implications were encountered, prompting investigation into the effects of phase aberrations on resulting focal spots, and experimental measurement of cone surface topology. We find the uniformity of the Fresnel cone shape and apex angle is crucial to the focussing properties. For polarimetry application, full details are provided for a single-shot full-Stokes polarimeter technique and proof-of-principle experiment, where broadband operation is demonstrated. I conclude by summarising the findings of my research and suggest potential future work in this area