Graphene-supported high-efficient modulation based on electromagnetically induced transparency in silica microcavity

The combination of graphene and high quality (Q) factor microcavity provides a promising way for realizing highefficient modulation. In this paper, an electro-optic tuning of a graphene-silica microdisk is investigated. Two graphene flakes, separated by Al2O3 isolation layer, are embedded in the silica microdisk to significantly enhance the light-matter interaction for the achievement of high-efficient modulation. Maximal resonant wavelength shift of 9.5 nm is presented as the bias voltage of about 189.5 V is applied on the graphene flakes, which is beneficial for realizing the optical modulation with the extinction ratio of about 16 dB. In addition, two partially reflecting elements are embedded in the waveguide which is side-coupled with the microcavity for realizing the electromagnetically induced transparency (EIT), subsequently achieving the high-efficient modulation with the extinction ratio of about 33.3 dB. Meanwhile, it is found that the 3 dB modulation bandwidth, maximum of as high as 58.1 GHz, gradually decreases as the thickness of Al2O3 isolation layer is reduced. As the potential applications, this improved study of graphene-silica microdisk opens up great potential for realizing high-efficient electro-optic devices such as modulator, optical switch and ultra-short pulsed laser.