# Hybrid tungsten oxyselenide/graphene electrodes for near-lossless 2D semiconductor phase modulators

## TL;DR

This paper introduces a new hybrid electrode material that enables efficient and low-loss optical phase modulation using 2D materials.

## Contribution

The novel hybrid tungsten oxyselenide/graphene electrode minimizes optical loss while enabling efficient phase modulation in 2D semiconductor devices.

## Key findings

- The hybrid TOS/Gr electrode achieves a high modulation efficiency of 0.202 V·cm.
- The device maintains a low extinction ratio change of 0.08 dB, indicating minimal optical loss.
- The design enables near-lossless phase modulation in TMD-based photonic devices.

## Abstract

Optical phase modulators are critical components in integrated photonics, but conventional designs suffer from a trade-off between modulation efficiency and optical loss. Two-dimensional materials like graphene offer strong electro-optic effects, yet their high optical absorption at telecom wavelengths leads to significant insertion losses. Although monolayer transition metal dichalcogenides (TMDs) provide exceptional telecom-band transparency for low-loss electro-refractive response, their practical implementation in phase modulators requires top electrodes to enable vertical electric field tuning, which typically introduces parasitic absorption. Here, we address this challenge by developing hybrid tungsten oxyselenide/graphene (TOS/Gr) electrodes that minimize optical loss while enabling efficient phase modulation in TMD-based devices. The UV-ozone-converted TOS (from WSe2) acts as a heavy p-type dopant for graphene, making the graphene transparent in the NIR region while enhancing its conductivity. Our complete device integrates a hybrid TOS/graphene transparent electrode with a hexagonal boron nitride dielectric spacer and monolayer WS2 electro-optic material on a SiN microring platform. This achieves a high modulation efficiency of 0.202 V·cm while maintaining an exceptionally low extinction ratio change of just 0.08 dB, demonstrating superior performance compared to modulators employing conventional electrodes. Our breakthrough in near-lossless phase modulation opens new possibilities for energy-efficient optical communications, photonic computing, and fault-tolerant quantum networks.