Implementation of a photorefractive arithmetic logic unit for multiwavelength information processing

We propose and demonstrate a multiwavelength arithmetic logic unit in photorefractive media wherein the polarization states of optical waves are used to encode the binary numbers 1 and 0. The process of writing and reading of photoinduced gratings in photorefractive media is utilized to implement and/or logic gates and an arithmetic full adder, which are the key elements of an arithmetic logic unit. To take advantage of wavelength-domain parallelism and to reduce the hardware needed for multibit operations, optical wavelengths are used to represent specific bits of binary words. Because of the broad bandwidth of optics, multiwavelength operations can be realized simultaneously within a single crystal. In this way, multibit operations can be performed in a single arithmetic logic unit. Experimental results are presented and discussed.