High-efficient and low-loss hybrid Si/VO2 absorption modulator electrically driven by graphene electrodes

Abstract

The phase change material vanadium dioxide (VO2) is suitable for building high-efficiency light modulators due to the different absorption efficiency of light in metallic and insulating states. The structure of an electro-absorption modulator based on VO2 and graphene proposed in this paper is formed by two layers of single-layer graphene wrapped around VO2, with a silicon waveguide in the middle and silica on both sides as the main path for light transmission. The input light of TE mode is limited to the SiO2 layer on both sides to increase the contact area with VO2 layers, which make it almost impossible to pass through when the metal electrode is connected to an external bias voltage and VO2 is in the metallic state. On the contrary, the input light passes through the main path of the modulation region with low loss without bias voltage. Finally, the modulator proposed in this paper has achieved a high extinction ratio of 27.3 dB and a low insertion loss of 0.66 dB (when VO2 is in insulating state) at a single wavelength of 1550 nm when the device length is 2 µm. In addition, the bias voltage of the modulator is 1.1 V with the modulation speed at 200 MHz, and the energy consumption is only 8.3083 fJ/bit at work, which is an ideal choice for photonic integrated systems today.