Compact, Energy-Efficient, High-Speed Electro-Optic Microring Modulator Based on Graphene-TMD 2D Materials

Abstract

The continued performance scaling of AI gigafactories requires the development of energy-efficient devices to meet the rapidly growing global demand for AI services. Emerging materials offer promising opportunities to reduce energy consumption in such systems. In this work, we propose an electro-optic microring modulator that exploits a graphene (Gr) and transition-metal dichalcogenide (TMD) interface for phase modulation of data-bit signals. The interface is configured as a capacitor composed of a top Gr layer and a bottom WSe₂ layer, separated by a dielectric Al₂O₃ film. This multilayer stack is integrated onto a silicon (Si) waveguide such that the microring is partially covered, with coverage ratios varying from 10% to 100%. In the design with the lowest power consumption, the device operates at 26.3 GHz and requires an energy of 5.8 fJ/bit under 10% Gr-TMD coverage while occupying an area of only 20 μm². Moreover, a modulation efficiency of V_πL = 0.203 V·cm and an insertion loss of 6.7 dB are reported for the 10% coverage. The Gr-TMD-based microring modulator can be manufactured with standard fabrication techniques. This work introduces a compact microring modulator designed for dense system integration, supporting high-speed, energy-efficient data modulation and positioning it as a promising solution for sustainable AI gigafactories.

Keywords: bandwidth; graphene; microring; modulator; power consumption; transition metal dichalcogenides.

Figure 1

Schematic of a composite of the Si-Gr-WSe₂ microring modulator. $W_{si}$ and $h_{si}$ are the width and height of both bus and ring waveguides.

Figure 2

Ring modulator scheme showing input/output signals and key device parameters. The dashed area is the portion of the ring covered by the Gr-TMD interface.

Figure 3

Microring modulator’s transmission curves for ON and OFF states with different amounts of ring coverage material.

Figure 4

Chemical potential difference (meV) and resonance shift (nm) when switching between ON/OFF states versus Gr-TMD coverage.

Figure 5

Variation of the effective index, measured in refractive index units (RIU), in terms of its real and imaginary parts versus chemical potential (eV).

Figure 6

Modulation efficiency (V·cm) and tuning efficiency (nm/V) versus Gr-TMD coverage.

Figure 7

Modulation bandwidth (GHz) and power consumption (fJ/bit) versus percentage of 2D material coverage. The dashed line indicates the ideal energy consumption limit.

Figure 8

Modulator’s figure of merit (GHz/(fJ·μm²)) versus percentage of 2D material coverage.