University of Cambridge
All-Optically Addressed Spatial Light Modulator and Diffractive Optical Element Based on Photoalignment of Azobenzene Polymer
Abstract
dc:description.abstractThe advancement of true three-dimensional (3D) displays hinges on the development of diffractive optical engines with high information bandwidth. However, conventional optical engines such as liquid crystal on silicon (LCOS) spatial light modulators (SLMs) and optically addressed SLMs (OASLMs) face scalability limitations in achieving smaller pixel sizes, wider diffraction angles, and greater information transmission capacity due to their reliance on electrical driving mechanisms. To overcome these challenges, this dissertation introduces an all-optically addressed spatial light modulator (AOASLM) that eliminates electrical driving and utilizes Pancharatnam-Berry (PB) phase modulation. The AOASLM operates through the in-plane reorientation of liquid crystal (LC) under the photoalignment of PAZO azobenzene. Leveraging this novel photoalignment technique, the research demonstrates repeatable information recording and holographic display capabilities with high phase modulation resolution, sub-wavelength pixel sizes, ultra-wide viewing angles, and superior information bandwidth. Such device also offers flexible size scalability, exemplified by the fabrication of an AOASLM measuring 420 mm ×300 mm. In-depth investigations into the physical and optical properties of PAZO azobenzene thin films were conducted, focusing on the minimum resolvable photoaligned pitch and the updatable photoreorientation properties essential for AOASLM operation. The study also delves into the optimization of the device structure to address excessive LC reorientation, enhancing the ability to refresh and the overall performance of AOASLM. Separately, this thesis explores the efficient fabrication of liquid crystal Pancharatnam- Berry diffractive optical elements (LC PB-DOEs). Conventional diffractive optical elements (DOEs) typically require expensive materials and complex, time-consuming fabrication processes. By utilizing optimized LCOS devices for precise phase modulation, this research demonstrates the fabrication of lightweight and multi-functional LC PB-DOEs. Implementing deep learning-assisted optimization successfully reduced the phase flicker magnitude in LCOS, which in turn enhances the quality of display images significantly and improves the accuracy of hologram replication during photo-patterning. The fabricated LC PB-DOEs exhibit superior holographic display quality with wide viewing angles, high contrast ratios, and tunable diffraction efficiency via electric fields. Applications of LC PB-DOEs such as a bifocal LC PB-lens and polarization-multiplexed holographic displays were successfully demonstrated, underscoring a wide range of practical usages of the this newly developed technology.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2024
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Wu, Weijie
- Advisor dc:contributor.advisor
-
- Chu, Daping
Subjects
dc:subject × 5Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.114324
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/377523