An all optical programmable logic gate

It is clear that if optical computing techniques are going to become a viable alternative to electronic techniques, they must not merely mimic electronics but provide capabilities above and beyond them. As an example of this the authors have recently demonstrated that a single nonlinear refractive bistable device can be used to provide the full adder capability (transmission providing the carry bit and reflection providing the sum bit) that requires at least five electronic gates to produce. An extension of this technique to include two coupled devices can be used to make an in-situ programmable logic gate capable of providing all eight two input Boolean functions (ON, AND, OR, XOR, NAND, NOR, XNOR, OFF) by varying holding beam power levels to each device