Design and simulation of linear logic gates in the two-dimensional square-lattice photonic crystals

We have proposed all-optical three-port AND, OR, XOR and NOT photonic crystal logic gates, based on modified symmetric T-branch combiners. Using the temporal coupled-mode theory the operation of the symmetric T-branch combiner has been investigated and the conditions which lead to a maximum power at the output port have been obtained. At the output port of the proposed devices, the logics 1 and 0 are defined as a more than 42% and a less than 14% of the transmission, respectively. The minimum intensity contrast ratio of the suggested logic gates is about 4.77 dB. The operations of the proposed devices are examined using time-domain transition-response simulations which have been performed using two dimensional finite-difference time-domain method.