Abstracts Category : Other

OPTICAL SIMULATION AND FABRICATION OF PANCHARATNAM(GEOMETRIC) PHASE DEVICES FROM LIQUID CRYSTALS

by Kun Gao

Pancharatnam made clear the concept of a phase-onlydevice based on changes in the polarization state of light. Adevice of this type is sometimes called a circular polarizationgrating because of the polarization states of interfering lightbeams used to fabricate it by polarization holography. Here, wewill call it a Pancharatnam (geometric) phase device to emphasizethe fact that the phase of diffracted light does not have adiscontinuous periodic profile but changes continuously. In thisdissertation, using simulations and experiments, we havesuccessfully demonstrated a 40 beam-steering device with >90%diffraction efficiency based on the Pancharatnam phase deflector(PPD) with the dual-twist structure. Unlike the conventionalPancharatnam phase deflector (c-PPD) limited to small diffractionangles, our work demonstrates that a device with a structuralperiodicity near the wavelength of light is highly efficient atdeflecting light to large angles. Also, from a similar fabricationprocedure, we have made an ultra-compact non-mechanical zoom lenssystem based on the Pancharatnam phase lens (PPL) with a lowf-number and high efficiency. The wavelength dependence on theimage quality is evaluated and shown to be satisfactory from redlight to near-infrared machine vision systems. A demonstrationdevice is shown with a 4 zoom ratio at a 633 nm wavelength. Theunique characteristic of these devices is made possible through theuse of azo-dye photoalignment materials to align a liquid crystalpolymer (reactive mesogens). Furthermore, the proposed dual-twistdesign and fabrication opens the possibility for making ahigh-efficiency beam-steering device, a lens with an f-number lessthan 1.0, as well as a wide range of other potential applicationsin the optical and display industry. The details of simulation,fabrication, and characterization of these devices are shown inthis dissertation.Advisors/Committee Members: Bos, Philip (Committee Chair).