Optical logic

Summary form only given. We report the theory and experimental demonstration of a laser device which performs the functions of binary arithmetic optically. Completely optical processing of logic functions could constitute a significant breakthrough in speed over conventional electronic processing. In our approach, input light pulses are assigned a binary code (0 or 1) according to their polarization along one of two mutually orthogonal directions. The response of the system to inputs of pairs of pulses consists of a pulse polarized along one of these initial orthogonal directions. The output pulse polarization can be made to correspond to those of the truth table for any of the logic operations of Boolean algebra. We report here achievement of the optical AND gate. The device is based on an optically excited dye laser whose cavity is birefringent. The birefringence reduces the degeneracy of the fundamental 479 mode to two orthogonal linear polarizations coincident with the birefringent axes. The input polarization controls the bistable polarization of the laser output by virtue of the photoselectively induced fluorescence dichroism of the dye medium. Relative adjustment of the respective thresholds for the two output polarizations provides the appropriate functional dependence for these logic operations. The experiment employed a Rh 6G jet stream dye laser pumped by a pulsed xenon ion laser. A novel two-beam polarizing interferometer generated the polarized input pulses. Further theoretical and experimental details will be presented, as well as an assessment of the future role of such devices.