Measurements of electrically tunable refractive index of MoS 2 monolayer and its usage in optical modulators

Two-dimensional materials hold a great promise for developing extremely fast, compact and inexpensive optoelectronic devices. A molybdenum disulphide (MoS 2 ) monolayer is an important example which shows strong, stable and gate tunable optical response even at room temperature near excitonic transitions. However, optical properties of a MoS 2 monolayer are not documented well. Here, we investigate the electric field effect on optical properties of a MoS 2 monolayer and extract the dependence of MoS 2 optical constants on gating voltage. The field effect is utilised to achieve ~10% visible light modulation for a hybrid electro-optical waveguide modulator based on MoS 2 . A suggested hybrid nanostructure consists of a CMOS compatible Si 3 N 4 dielectric waveguide sandwiched between a thin gold film and a MoS 2 monolayer which enables a selective enhancement of polarised electro-absorption in a narrow window of angles of incidence and a narrow wavelength range near MoS 2 exciton binding energies. The possibility to modulate visible light with 2D materials and the robust nature of light modulation by MoS 2 could be useful for creation of reliable ultra-compact electro-optical hybrid visible-light modulators.