Ultra-fast 1-bit comparator using nonlinear photonic crystalbased ring resonators

In this paper, a photonic crystal structure for comparing two bits has beenproposed. This structure includes four resonant rings and some nonlinear rods. Thenonlinear rods used inside the resonant rings were made of a doped glass whose linearand nonlinear refractive indices are 1.4 and 10-14 m2/W, respectively. Using Kerr effect,optical waves are guided toward the correct output ports. In this study, plane waveexpansion and finite difference time domain methods were used for calculation ofphotonic bandgap and simulation of optical wave propagation, respectively. The size ofthe proposed structure is 1585 μm2 which is more compact than the previous works.Furthermore, the obtained maximum delay time is about 2 ps that is proper to highspeedprocessing. The normalized output power margins for logic 0 and 1 are calculatedas 25% and 71%, respectively. According to the obtained results, this structure can beused for optical integrated circuits.