Theoretical investigation of silicon MOS-type plasmonic slot waveguide based MZI modulators

In this paper, a Mach-Zehnder silicon nanoplasmonic electro-optic modulator is proposed and theoretically analyzed. It is composed of horizontal metal-SiO2-Si-metal plasmonic slot waveguides for phase shifting and ultracompact V-shape splitter/combiner to link the plasmonic slot waveguides and the conventional Si dielectric waveguides. The proposed modulator can be directly integrated into existing Si electronic photonic integrated circuits (EPICs) and be fabricated using standard Si complementary metal-oxide-semiconductor (CMOS) technology. The modulator's parameters are optimized through systematic 2-dimensional numerical simulations. For a modulator with 3-µm-long Ag-SiO2(2 nm)-Si(50 nm)-Ag phase shifter and 0.35-µm-long splitter/combiner operating at 1.55-µm wavelength, simulation shows an insertion loss of ~-8 dB, an extinction ratio of ~7.3 dB - with a switching voltage of ~5.6 V, and a bandwidth of ~500 GHz. A possible approach to reduce the switching voltage is addressed.