Effect of Structural Disorder on Photonic Crystal Logic Gates

In this paper, we study the effect of structural disorder on photonic crystals logic gates applying a new approach based on the evaluation of two metrics: the error rate (ER) and the mean absolute deviation of transmission of the error cases (MATEC). ER is the probability that a fabricated photonic crystal logic gate does not accomplish its logic function correctly, and MATEC measures the imperfection degree of the device through the transmission coefficient. The process consists in introducing disorder in specific regions in the boundary of the waveguides that form the logic gate structure. A significant number of simulations is randomly performed for each input combination of the logic gate. The ER and MATEC are calculated, and the process is replicated 20 times with different seed numbers. Finally, a statistical test T is carried out to establish the most critical regions for the device. We evaluate some photonic crystal logic gates with different lattice configurations using this approach. The results show that, for structures with a triangular lattice, regions in the corners and close to the output are more critical to ER and MATEC, respectively. For structures with a square lattice, we found that the intersection regions are the most sensitive for both metrics. As a final consideration, we remark that this methodology can be easily applied to evaluate other kinds of disorder and to analyze photonic crystals devices based on waveguides with different lattice configurations, and can guide the design of future robust gates.