Invention:
This technology consists of a process to fabricate micro-polarizer and wave plate based on nematic liquid crystals. University of Arizona inventors have improved upon that technology and have identified a process to create a circular polarizer for various visible wavelengths using a cholesteric liquid crystal (ch-LCP).
Background:
Linear micropolarizer arrays have been fabricated using a variety of techniques including; etched dichroic polymers, wire-grid polarizers, liquid crystal (LC) arrays, and photo aligned liquid crystal polymers (LCP). Unfortunately, these techniques are exclusively applied to the fabrication of linearly polarized elements. Making circular and elliptical polarization elements are more difficult to construct. A circular polarizer can be constructed by using a multilayer structure, such as the combination of a wave plate, a linear polarizer and absorbent dyes. The wire-grid polarizer technology is not easily extended to non-linear polarization, therefore liquid crystal polymers mixed with chiral dopants, i.e., cholesteric liquid crystal polymers can be an effective and potentially simpler alternative for creating patterned non-linear polarized optical devices. Like nematic liquid crystals, cholesteric liquid crystals can be photo-aligned using techniques such as atomic force microscopes, and ion beams. Although, these techniques can be easily extended to cholesteric liquid crystals, they are not conducive for large areas. To photo-align cholesteric liquid crystals on large areas, implementing the use of polarized light would be effective because polarized light has been demonstrated to fabricate linear polarizers of sizes as small as 4um over large areas.
Advantages:
- No need of wave plates to generate circularly polarizing light
- The process is simple and inexpensive compared to other micropolarizer systems
- Simpler and more conducive technology than competition, ie. wire grid polarizers, which require sophisticated lithography and etching toolsets for fabrication. Wire grid polarizers also do not translate well for the fabrication of non-linear polarized optical devices. *Circular polarizers are achieved with a single layer and no absorbing dyes.
- This process also utilizes two different patterning methods, both of which are simple and inexpensive compared to other micropolarizer systems
Applications:
- Fabricate micro-polarizers on optical filters and on sensor arrays
- Circular polarizers for optical array sensors include CCD and CMOS
- Three dimensional displays, interferometry, optical storage, polarimeters, cameras
Status: issued U.S. patent #9,671,538
