All-optical half adder based on cross structures in two-dimensional photonic crystals

Abstract

We propose an all-optical half adder based on two different cross structures in two-dimensional photonic crystals. One cross structure contains nonlinear materials and functions as an "AND" logic gate. The other one only contains linear materials and acts as an "XOR" logic gate. The system is demonstrated numerically by the FDTD method to work as expected. The optimal operating speed without considering the response time of the nonlinear material, the least ON to OFF logic-level contrast ratio, and the minimum power for this half adder obtained were 0.91 Tbps, 16 dB and 436 mW, respectively. The proposed structure has the potential to be used for constructing all-optical integrated digital computing circuits.