A One-Bit Optical Numerical Comparator With High Extinction Ratio Based on Graphene–Silicon Microring Resonators

Microring resonators (MRRs) are the important devices for the development of silicon-based optoelectronic integrated chips. Their composition of optical modules, such as optical modulators, switches, and optical logic gates, have greatly contributed to the development of the silicon-based optoelectronics. However, due to the large radius of MRRs and the weak optical interaction of the silicon material itself, how to further improve integration and reduce power consumption is a great challenge. Combining graphene, which has many unique properties, with silicon-based MRRs provides a good solution. Therefore, based on the interaction principle of graphene and light and the transmission principle of all-pass silicon-based MRRs, this article proposes for the first time a one-bit optical numerical comparator based on MRRs, whose structure consists of four silicon-based MRRs with a radius of 1.8 μm covering a single layer of graphene. The logic function of the one-bit optical numerical comparator is realized by adjusting the different chemical potentials of the graphene. Simulation results shows that, with a TE mode light source at 1555.21 nm, the proposed optical numerical comparator obtains a minimum extinction ratio of 19.7 dB and a contrast ratio of 19.7 dB. Compared with the previously reported optical numerical comparators based on silicon-based MRRs or ring resonators, the proposed optical numerical comparator has many advantages, such as high extinction ratio, high contrast ratio, compact structure, and high stability. It is beneficial to the development of silicon-based photonic integrated devices.