Digital Optical Computing With Ferroelectric Liquid Crystals

Abstract

Many optical computing schemes employ either intensity-based logic or polarization-based logic. Intensity-based logic utilizes the absence or presence of light to represent the binary logic states 1 and 0, thus dissipating light after each operation. Polarization-based logic uses orthogonal states of polarization to represent its two binary states. This has the advantage that no light is lost in performing cascaded logic operations. Surface stabilized ferroelectric liquid crystal (SSFLC) devices, which can function as half-wave plates, can be used to implement polarization-based parallel optical logic gates. Under the influence of an applied electric field, a properly oriented SSFLC device rotates the polarization of incident light through 90°. By using SSFLC matrix arrays, the light passing through selected pixels can be rotated independently of adjacent pixels. Operating characteristics of a 4 X 4 SSFLC matrix array including contrast ratio, switching speed, switching voltage, and rotary transmission are presented. A matrix addressing scheme is discussed and implemented with a SSFLC. Using two SSFLC matrix arrays, we demonstrate the XOR/XNOR logic operations along with measurements of the percentage of polarized light rotated into the output binary states.