Polarization control investigation based on an integrated graphene-assisted microring cavity

Abstract

In this paper, we propose and analyze an integrated polarization-selective structure of a graphene-assisted silica microring cavity to realize polarization control due to different optical distributions of whispering-gallery modes in the microring and polarization-dependent absorptions of graphene. A graphene stripe is partially side coupled with a silica microring to distinctly influence the propagations of a TE mode and TM mode in the microring. Especially, the appearance of the plasmonic mode in the groove between the graphene and the microring enhances light–matter interaction between the graphene and the TM-polarized mode, while without that for the case of TE mode propagation. By applying voltage on the graphene stripe along with its electro-optic modulation effect, the difference in the polarization extinction ratio of 20.6 dB is obtained between the cases of the polarized TM mode and TE mode in the microring. Furthermore, a second silica microring is added in this hybrid structure to couple the original microring along with a graphene stripe embedded in between finally realizing an electromagnetically induced transparency line shape because of the plasmonic coupling in both cavities with the condition of TM mode propagation, while without any line-shape change for the case of TE mode propagation. This compact hybrid structure offers a good integrated photonic platform to realize an excellent polarization-selective device.