Reduction of the Scattering Effect of Vertically Aligned Polymer Stabilized Liquid Crystal by Curing Voltage
Date Issued
2014
Date
2014
Author(s)
Li, Yan-Min
Abstract
Liquid crystal technologies have been used in our daily life. It has not only been utilized in displays but also in other applications such as Fabry-Perot interferometers in wavelength division multiplexing (WDM). Liquid crystal has a characteristic that it would change its molecular orientation when a voltage is applied. The time it takes to rotate is called response time. For display and many other applications, this is a very important parameter. For example, the display images would appear as a continuous motion for human visual system if response time is smaller than time interval that can be distinguished by human eyes. Due to its fast response time, it can also be used as rapid shutters for optical instruments or used as privacy glass. Polymer Stabilized Liquid Crystal (PSLC) is one kind of liquid crystal (LC) gel that has been reported. It is composed of liquid crystal and monomer under certain ratio. After UV curing, monomers would become polymers which can help LC molecules restore back to original state more quickly when a lower voltage is applied. Hence, the LC decay time can be shortened. On the other hand, the rise time can be improved by applying an overdrive voltage. PSLC usually has a common phenomenon which is that, after an applied voltage, the LC molecules would tilt randomly which causes strong scattering. This is due to the structure of the formed polymer which does not allow LC molecules to tilt consistently. In this thesis, a curing voltage was found to be able to help reduce the strong scattering effect of the VA-PSLC (Vertical Alignment PSLC) significantly. It therefore can have a high on-state transmittance. We take the advantage of fast response time of PSLC and place it inside a Fabry-Perot cavity to achieve a wavelength tunable filter. These filters can have potential applications in wavelength tuning applications (e.g. WDM) in telecommunication systems where high speed is desirable.
Subjects
polymer stabilized liquid crystal (PSLC)
Liquid Crystal
curing voltage
Fabry-Perot filter
wavelength tuning
Type
thesis
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