Polarization-based optical logic gates in photorefractive crystals

Abstract

Optical logic in photorefractive crystals has been extensively studied1. Some logic gates such as AND and XOR were achieved based on photo-induced volume gratings, where the logic values ‘1’ or ‘0’ are represented by the presence or absence of light beams. One disadvantage of this encoding method is that some logic gates can only be obtained by the cascading of other logic gates, making it cumbersome and inefficient. In this paper, we propose and demonstrate logic gates whose values are represented by the polarization state of light2, i.e., ordinary and extraordinary beams in photorefractive crystals. Some advantages are that 1) switching between two logic states, or, a NOT gate can be easily achieved using a standard half-wave plate, and 2) the two logic states are both represented by the presence of light beams. We demonstrate that all sixteen two-input binary logic gates can be easily achieved without cascading. Two inputs are represented by the two writing beams with respective polarization states. As well, the output value of the logic gate is represented by the polarization state of the diffracted beam. We also demonstrate a polarization based optical full adder.