Wide-band spatially tunable and hyper-reflective photonic bandgap based on a refilled cholesteric liquid crystal polymer template

Abstract

The scientists in the field of liquid crystal (LC) exploited chiral LC polymer to fabricate novel cholesteric LC (CLC) polymer template (simply called template) in recent years The template can effectively overcome the limitation in the optical features of traditional CLCs such as enhancement of reflectivity over 50% multiple photonic bandgaps (PBGs) and changeable optical characteristics by flexibly replacing the refillingLC materials and so on This thesis fabricates two gradient-pitched CLC templates with two opposite handednesses which are then merged as a spatially tunable and hyper-reflective CLC template sample This sample can simultaneously reflect right- and left-circularly polarized lights and the tunable spectral range includes the entire visible region In addition this study investigates the causes to limit the reflectance of the template sample and a method to improve the reflectance By increasing the temperature of the template sample exceeding the clearing point of the refilling LC the light scattering significantly decreases and the reflectance effectively increases In summary this study fabricates a merged template sample to develop a wide-band spatially tunable and hyper-reflective PBG device This device has a maximum reflectance over 85% and a wide-band spatial tunability in PBG between 400 nm and 800 nm which covers the entire visible region This hyper-reflective PBG template device with a wide-band tunability over entire visible region can not only be employed as a wide-band spatially tunable filter but also used to develop a low-threshold mirror-less laser with a spatial tunability at entire visible region and simultaneous emission of left- and right-circular polarizations

Date of Award	2014 Aug 25
Original language	English
Supervisor	Chia-Rong Lee (Supervisor)