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Title: Characterisation of phase modulating liquid crystal on silicon devices
Author: Lee, Y.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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The objective of the work described in this thesis was to optimize the optical phase modulating properties of liquid crystal on silicon (LCoS) devices for non-display applications. This thesis presents the characterization of oxide two deposition processes, modelling of binary phase modulation in ferroelectric liquid crystal SLMs using electronic equivalent circuit, and characterization of multi-phase modulation in nematic liquid crystal with pulse-width modulation. For optimal optical performance of a phase modulating LCoS device, the degree of surface planarisation of the CMOS backplane has to be superior to that of conventional CMOS. Two oxide-deposition processes have been characterized to evaluate their effectiveness in planarising microdisplay backplanes. In order to investigate the trench-filling capabilities of the respective oxide deposition processes, I prepared test samples that had a set of trench patterns (1 - 6 μm wide) etched into 4 μm -thick thermal oxide on a Si-substrate. I found that the trench filling capability of an electron cyclotron resonance chemical vapor deposition (ECR CVD) process is superior to that of a pyrolytic CVD process. I investigated the effects of ECR CVD deposition parameters on trench-filling properties and demonstrated the ability to produce deposited oxide layers which fill high aspect ratio trenches without producing voids. Modelling of binary phase modulation is required for optimal performance of ferroelectric liquid crystals on silicon SLMs when used in coherent optical systems. This thesis presents a modelling technique by which an HSpice model can be provided for characterization of phase modulation properties for designing FLC-on-silicon SLMs. The simulation and experimental measurements of phase modulation are described. For the theoretical model simulation, FLC parameter measurements are described. I experimentally verified the modeled prediction of phase modulation by investigating reflective FLC test cells. I have shown reasonable agreement within 9 % between the measured and simulated values of phase modulation. In phase modulating diffractive optical devices multi-phase modulation provides improved performance over binary modulation. Multi-phase modulation can be achieved by using nematic liquid crystal spatial light modulators (NLCSLM) with pulse-width modulation driven from a binary CMOS backplane. This thesis presents the characteristics and the driving scheme of the 512x512 Si-backplane SLM for the implementation of the multi-phase modulation while comparing the binary and four-level phase holograms. A diffraction efficiency of 39.7% for binary grating and 72.7% for four-level blazed grating were obtained at a spatial frequency of 0.78 lines per mm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available