boolean logic functions are provided in a programmable optical logic device by combining a symmetric self - electrooptic effect device with a logic control element for optically programming the s - seed to initiate logic operations from a predetermined state . the predetermined preset state together with subsequent application of optical data signals to the s - seed permit the desired logic operation to be performed on the optical data signal by the optical logic device . logic operations which may be programmed into the optical logic device include and , nand , or and nor functions . a complementary pair of optical signals is provided as output from each optical logic device .