Fast, Fringing Field Free, Optical Phase Modulation Using Ferroelectric Liquid Crystals by YUAN Zhengnan Department of Electronic and Computer Engineering The Hong Kong University of Science and Technology Abstract The fast phase modulations of light are attractive topics for advanced photonic and display research over decades. They are key technologies in many sophisticated applications, like remote sensing, adaptive optics, biomedical sensing, Virtual Reality (VR), hologram, Light Detection and Ranging (LiDAR), and Wavelength Selective Switch (WSS). However, challenges still exist, like slow response time, high driving voltage, low phase depth, Fringing Field Effect (FFE), low efficiency, limited Field of View (FoV), and high cost. In this aspect, fast ferroelectric liquid crystals (F...[ Read more ]

Fast, Fringing Field Free, Optical Phase Modulation Using Ferroelectric Liquid Crystals by YUAN Zhengnan Department of Electronic and Computer Engineering The Hong Kong University of Science and Technology Abstract The fast phase modulations of light are attractive topics for advanced photonic and display research over decades. They are key technologies in many sophisticated applications, like remote sensing, adaptive optics, biomedical sensing, Virtual Reality (VR), hologram, Light Detection and Ranging (LiDAR), and Wavelength Selective Switch (WSS). However, challenges still exist, like slow response time, high driving voltage, low phase depth, Fringing Field Effect (FFE), low efficiency, limited Field of View (FoV), and high cost. In this aspect, fast ferroelectric liquid crystals (FLCs) are promising candidates here, due to their merits such as no FFE, fast response time (microsecond), and low driving voltage.

In this thesis, we propose two novel binary phase modulation systems and one continuous phase modulation system, utilizing Electrically Suppressed Helix Ferroelectric Liquid Crystals (ESHFLCs) and vertically aligned Deformed Helix Ferroelectric Liquid Crystals (VADHFLCs), respectively. Moreover, the FFE analysis and new dielectric wall design on Liquid Crystals (LCs) reveal more solutions for further applications.

As for binary phase modulation, firstly, a LiDAR system using FLC Dammann Grating (FLCDG) is proposed. It replaces iterative scanning and enables fast one-shot translational and rotational detection (>50 kframs/s). Secondly, we propose a fast (50 μs) switchable lenses system with 8 focal points, which is the key to solving bottlenecks in VR. As for continuous phase modulation system, we disclose a fast, hysteresis-free, FFE-free, continuous 2π modulation with 96% reflectance, utilizing the Kerr effect in VADHFLC. It is the 1st-time found that no FFE in VADHFLC, even for the phase modulator with 1 μm modulation size. Moreover, the highest Kerr constant (240 nm/V2) at the communication band is achieved for the 1st time with the demonstration using blazed grating. These new findings pave the way for the large-capacity intelligent optical telecommunication system and next-generation phase modulators for ultra-high-resolution display and photonic applications.