Novel methods for enhanced free electron laser output

An emerging area of free electron laser development concerns tailoring the transverse and phase profile of the light, which can result in the radiation acquiring orbital angular momentum. This thesis studies the development of novel techniques for free electron lasers with consideration of the generation of higher-order orbital angular momentum modes acting as a starting point for this research. Three new techniques are presented in this thesis. The first examines altering mode competition in a free electron laser to induce radiation of a dominant orbital angular momentum mode. The next is a scheme to produce light with spatially varying states of polarisation - obtained through the overlap of different coherent transverse light distributions. The third technique produces trains of short radiation pulses where the properties of the pulses alternate. The goal of this research is to increase the diversity of radiation from free electron lasers in order to offer something new and unlock new areas of scientific research.