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Process to Fabricate Micro-Polarizers and Waveplates on Sensor Array

Case ID:
UA11-058
Description:

Background:

Patterned polarizers have a variety of applications in polarimetry, interferometry, three dimensional displays, and optical data storage. 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). Wire-grid polarizers are by far the most common commercial products for infrared applications; however, micropatterned wire-grid polarizers have limited spatial resolution and poor performance at visible wavelengths, require complicated lithographic processing, are susceptible to defects and cannot be easily extended to non-linear polarizations. An alternative and potentially simpler technology to create patterned polarizers is the photo alignment of absorbing materials which can produce micron sized polarizers of high efficiency and extinction for ultra violet (UV), visible, and near infrared (NIR) wavelengths.

Micropatterned LC alignment has been demonstrated using atomic force microscopes, ion beams, oblique angle gold deposition, and photo alignment using polarized laser light. While smaller resolution alignment has been demonstrated using the first two techniques, it is impractical for large areas. The use of linearly polarized ultraviolet (LPUV) radiation to align linearly photopolymerizable polymers (LPP) has been under intense research for many years as a noncontact replacement for traditional mechanical buffing. Photo alignment of LCPs has been demonstrated over large areas and with features as small as 2.5 microns. Many different LPP materials have been explored including azodye and dye doped polymers, polyimide, and cinnamoyl or coumarin side-chain polymers.

This invention demonstrates the use of multiple layers of an LPP/LCP system to create more complex polarization elements such as color circular polarizers.

Invention:

The inventors have developed a fabrication process to create patterned polarizers for various visible wavelengths using dichroic dye in a liquid crystal polymer (LCP) host directly on an array of optical sensors. Contact lithography is used to pattern a thin alignment layer, which subsequently transfer the pattern to the LCP. Waveplates of arbitrary retardance and linear and circular polarizers can be fabricated using multiple layers of LCP. Examples of optical sensors include charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS). The process is simple and inexpensive compared to other micropolarizer systems. The main competitors are wire grid polarizers, which require sophisticated lithography and etching toolsets for fabrication. In addition, circular polarizer cannot be implemented using wire grid configurations. Dichroic liquid crystal micro-polarizers use self-assembly to generate unique polarization domains without metallization or etching.

Advantages:

  • Waveplates of arbitratry retardance and linear and circular polarizers can be fabricated using multiple layers of LCP.
  • The process is simple and inexpensive compared to other micropolarizer systems. The main competitors are wire grid polarizers, which require sophisticated lithography and etching toolsets for fabrication.
  • Circular polarizers can be manufactured which cannot be implemented using wire grid configurations.

Application:

  • Fabricate micro-polarizers and waveplates on optical filters and on sensor arrays.
  • Waveplates and polarizers for optical array sensors include CCD and CMOS.
  • Three dimensional displays, interferometry, optical storage, polarimeters, cameras.

Status:

Inventors have reduced this technology to practice and have demonstrated the ability to create linear polarizers using a two layer liquid crystal system. The highest extinction ratio measured for a blue polarizer was 40.1 at 633 nm. It is expected that extinction ratios over 1000 can be achieved using higher dye concentrations. The smallest feature resolved is 3.1 microns using contact lithography. The demonstration of an integrated patterned circular polarizer allows for new imaging polarimeters which can measure all four Stokes parameters as well as other polarization or wavefront sensing applications. The patent application has published on May 3, 2012 as Pub. No. US 2012/0105783 A1.

Lead Inventor: Stanley Pau

UA ID: UA11-058

 

Patent Information:
For Information, Contact:
Amy Phillips
Optics Licensing Specialist
The University of Arizona
520-626-9579
aphillips@ott.arizona.edu
Inventors:
Stanley Pau
Graham Myhre
Keywords:
liquid crystal
polarimetry
polarizer
waveplate
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