Experimental realization of an optical digital comparator using silicon microring resonators

We propose and experimentally demonstrate a silicon photonic circuit that can perform the comparison operation of two-bit digital signals based on microring resonators (MRRs). Two binary electrical signals regarded as two operands of desired comparison digital signals are applied to three MRRs to modulate their resonances through the microheaters fabricated on the top of MRRs, respectively (here, one binary electrical signal is applied to two MRRs by a 1×2 electrical power splitter, which means that the two MRRs are modulated by the same binary electrical signal). The comparison results of two binary electrical signals can be obtained at two output ports in the form of light. The proposed device is fabricated on a silicon-on-insulator substrate using the complementary metal-oxide-semiconductor fabrication process, and the dynamic characterization of the device with the operation speed of 10 kbps is demonstrated successfully.