Liquid crystal devices for optical beam control

Thesis

This thesis investigates the development of liquid crystal (LC) devices for deployment in advanced optical beam control, with a focus on their potential to enhance precision, efficiency, and versatility in various optical applications. The key innovations of this work include the development of diffractive optical elements, new intensity adaptive optics (I-AO) systems and a generator of optical quasiparticles using LC devices.

For the development of direct laser written (DLW) diffractive optical elements, such as Dammann gratings and computer-generated holograms (CGHs), they are fabricated using two-photon polymerisation (TPP) DLW, achieving diffraction efficiencies above 60% and response times of 20 ms for thin (5 μm) devices and 120 ms for thick (20 μm) devices. The thesis also presents significant advances in intensity-based adaptive optics (I-AO) systems, proposing the I-AO aberration corrector with corresponding calibration methods and utilising dual-loop feedback correction mechanisms along with sensor-based and sensorless methods to correct the intensity aberrations. This system improves intensity distribution uniformity under aberrations and enables control of the total energy level at the pupil plane, distinguishing it from conventional phase-only adaptive optics (AO) and expanding the existing AO toolboxes. Furthermore, the thesis explores the generation of optical quasiparticles, including optical skyrmions and optical merons, through cascaded LC spatial light modulators (SLMs). The proposed structure allows for the dynamic manipulation of the beam polarisations, providing flexibility in optical quasiparticle generation. The generated optical quasiparticles demonstrate topological protection against combinations of various perturbations (e.g. attenuators, retarders and depolarisers) with experimental robustness exceeding 90%.

Future work will focus on refining LC mixtures for faster response times, developing advanced I-AO correction algorithms, and exploring the potential of optical quasiparticles for optical computing and high-bandwidth communications.

Authors: Zhao, Z

• DOI: 10.5287/ora-00yx5mv25
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English