In this paper a novel design of all-optical half-subtractor based on nonlinear
directional coupler is proposed. By using four waveguides and appropriately
adjusting the refractive indices and selecting the proper length of waveguides, halfsubtractor
function can be obtained. The operation of this function is simulated by
RSoft CAD-Layout (BeamPROP) simulator. The simulation results confirm the alloptical
half-subtractor circuit without any optoelectronic conversions.
