Low-loss phase modulation using a MoS₂ monolayer integrated on silicon waveguides

Abstract

Two dimensional (2D) materials are at the forefront of research in integrated modulators. However, achieving pure phase modulation with low insertion loss remains challenging in 2D material modulators. This work explores phase modulators based on monolayer MoS2 integrated on a Si photonic platform. We investigated the electro-optical response of MoS2 using two device architectures: a monolayer MoS2 integrated on a doped Si waveguide and a MoS2–Al2O3–MoS2 capacitor integrated on an undoped Si waveguide. At a wavelength of 1550 nm, the integration of MoS2 in both architectures induces minimal optical insertion losses. Specifically, the single-layer device on a doped silicon waveguide achieves a phase modulation efficiency of 0.53 V·cm, with propagation losses dominantly originating from the doped silicon (108 dB ). The MoS2–Al2O3–MoS2 modulator has a low propagation loss of 6.4 dB and modulation efficiency of 1 V·cm. Depending on the resistance–capacitance constant, a trade-off exists between achievable modulation efficiency, electro-optical bandwidth, and insertion loss. The strong and lossless electro-refractive response makes MoS2-based phase modulators suitable for a variety of applications such as light detection and ranging, optical switching, quantum and optical neural networks, and coherent optical communication.