Phase control with spatial-light modulators towards application for opto-optical modulation

Abstract: This project is about focusing a Gaussian laser beam that has a spatial phase profile applied by a spatial light modulator. The goal is to be able to control the shape, position and phase of the peak at the focus and to split up the peak at the focus into several peaks. Controlling the profile of the beam at the focus has interesting applications for opto-optical modulation. A code was written in Matlab that simulates the focusing of a Gaussian beam. Within the code a phase profile can be applied to the Gaussian beam profile. The phase profiles that are tested are linear profiles and curved profiles. A function is written that combines phase profiles by alternating between pixels. This splits up the peak the focus into several peaks. It was found that by combining linear phases through alternating between pixels the peaks at the focus can be split up into several peaks. However, when doing so, a number of extra peaks appear at the focus. The origin of the extra peaks is not explained in this thesis, but their behaviour and consequences are studied. It was also found that the peaks can be controlled in time by applying a flat phase profile, and that the shape of the peak at the focus can be adjusted by applying a curved phase profile.