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 MoS 2 integrated on a Si photonic platform. We investigated the electro-optical response of MoS 2 using two device architectures: a monolayer MoS 2 integrated on a doped Si waveguide and a MoS 2 –Al 2 O 3 –MoS 2 capacitor integrated on an undoped Si waveguide. At a wavelength of 1550 nm, the integration of MoS 2 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ). The MoS 2 –Al 2 O 3 –MoS 2 modulator has a low propagation loss of 6.4 dB <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> 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 MoS 2 -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.