Two-dimensional photonic crystal-based half adder: a review

The advanced technological development of photonics is very rapid compared to other technologies. Photonic crystal (PC)-based combinational and sequential circuits are most widely used for photonic integrated circuits. In this paper, we have mainly focused on the adder where the output is a pure function of the present input only. A half adder is a type of adders, which adds two binary digits and gives an output plus a carry value. The half adder contains two input ports and two output ports as sum and carry. In this attempt, two-dimensional (2D) PCs-based half adders that are designed either square or triangular lattice using various mechanisms with different materials are presented here. The adders are most widely used in program counters, digital instruments and in microcontrollers.