Micropatterned Photoalignment for Wavefront ControlledSwitchable Optical Devices

by Nikolaus Glazar

Institution: Kent State University
Year: 2016
Keywords: Chemical Engineering; Physics; Chemistry; Liquid Crystal; Liquid Crystal Devices; Photoalignment; Automated Photoalignment; Maskless Photoalignment; LC; Pancharatnam Phase; Geometric Phase; Berry Phase; PB-phase Transparent Display; Liquid Crystal Gratings; SD1; Phase Mask; DMD; Sub-diffraction
Posted: 02/05/2017
Record ID: 2066911
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=kent1460650961


Photoalignment is a well-established technique for surface alignment of the liquid crystal director. Previously, chrome masks were necessary for patterned photoalignment but were difficult to use, costly, and inflexible. To extend the capabilities of photoalignment we built an automated maskless multi-domain photoalignment device based on a DMD (digital multimirror device) projection system. The device is capable of creating arbitrary photoalignment patterns with micron-sized features. Pancharatnam-Berry phase (PB-phase) is a geometric phase that arises from cyclic change of polarization state. By varying the azimuthal anchoring angle in a hybrid-aligned liquid crystal cell we can control the spatial variation of the PB-phase shift. Using our automated photoalignment device to align the liquid crystal arbitrary wave front manipulations are possible. The PB-phase shift effect is maximized when the cell is tuned to have a half-wave retardation and disappears at full-wave retardation, so the cell can be switched on and off by applying a voltage. Two wavefront controlled devices developed using this technique will be discussed: A switchable liquid crystal phase shift mask for creating sub-diffraction sized photolithographic features, and a transparent diffractive display that utilizes a switchable liquid crystal diffraction grating. Advisors/Committee Members: Yokoyama, Hiroshi (Committee Chair).