Mode transforming vortex laser with optical levitation

The work in this thesis spans two primary fields of inquiry. The first focuses on the development of a novel laser system capable of direct optical vortex (OV) emission, while the second aims to demonstrate its application in the optical levitation of reflective hollow microspheres. We first present the non-standard use of a wedge-plate shearing interferometer (WPSI) as a TEM00 Gaussian to LG01 OV mode conversion device. A detailed description of its geometric configuration and interferometric process is presented. It gives an idealised power conversion of 99.6 % in favour of the of the LG01 OV-mode. However, since the OV is generated in its face-reflection, the incident power conversion is equal to only its Fresnel reflectance. Power scaling potential is improved through intracavity use of the WPSI. A unidirectional ring cavity was used with a 20:1 power imbalance in favour of clock- wise propagation which enhanced incident power to enable watt-level OV output power (1.15 W). The unconverted power is recycled back into the cavity. In this configuration we demonstrate the generation of OV beams with high beam-quality (M2 = 1.94, 2.09) and high LG01 mode-purity (97.8 %). In the second part, we demonstrate the use of this system in optical levitation. This work was motivated by the desire to levitate metallic (possible reflective) hollow-sphere (shells with low internal refractive index) targets for experiments with high-intensity, high-energy laser systems particularly in the generation of high-density plasmas, point X-ray sources, and charged-particle acceleration. We demonstrate the optical levitation of shells 20 to 110 μm in diameter (masses of 25 ng to 230 ng) at long focal length (f = 40 mm) and measure <5 μm spatial stability in air and low vacuum.