Characterize and optimize the four-wave mixing in dual-interferometer coupled silicon microrings**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0303700), the National Natural Science Foundation of China (Grant Nos. 61632021, 11627810, 11690031, and 11621091), and Open Funds from the State Key Laboratory of High Performance Computing of China (HPCL, National University of Defense Technology).

Abstract

By designing and fabricating a series of dual-interferometer coupled silicon microrings, the coupling condition of the pump, signal, and idler beams can be engineered independently and then we carried out both the continuous-wave and pulse pumped four-wave mixing experiments to verify the dependence of conversion efficiency on the coupling conditions of the four interacting beams, respectively. Under the continuous-wave pump, the four-wave mixing efficiency gets maximized when both the pump and signal/idler beams are closely operated at the critical coupling point, while for the pulse pump case, the efficiency can be enhanced greatly when the pump and converted idler beams are all overcoupled. These experiment results agree well with our theoretical calculations. Our design provides a platform for explicitly characterizing the four-wave mixing under different pumping conditions, and offers a method to optimize the four-wave mixing, which will facilitate the development of on-chip all-optical signal processing with a higher efficiency or reduced pump power.