High-Contrast Electro-Optic Modulation of a Photonic Crystal Nanocavity by Electrical Gating of Graphene

TL;DR

This paper demonstrates a high-contrast, low-power electro-optic modulation technique using a graphene-integrated photonic crystal nanocavity, achieving significant reflection and wavelength tuning, advancing integrated photonic device capabilities.

Contribution

It introduces a novel graphene-based nanocavity modulator with high contrast and low voltage operation, enabling efficient control of optical properties in silicon photonics.

Findings

Over 10 dB reflection modulation at 1.5 V swing voltage

Resonance wavelength shift of nearly 2 nm

Q factor modulation exceeding threefold

Abstract

We demonstrate a high-contrast electro-optic modulation of a photonic crystal nanocavity integrated with an electrically gated monolayer graphene. A high quality (Q) factor air-slot nanocavity design is employed for high overlap between the optical field and graphene sheet. Tuning of graphene's Fermi level up to 0.8 eV enables efficient control of its complex dielectric constant, which allows modulation of the cavity reflection in excess of 10 dB for a swing voltage of only 1.5 V. We also observe a controllable resonance wavelength shift close to 2 nm around a wavelength of 1570 nm and a Q factor modulation in excess of three. These observations allow cavity-enhanced measurements of the graphene complex dielectric constant under different chemical potentials, in agreement with a theoretical model of the graphene dielectric constant under gating. This graphene-based nanocavity modulation demonstrates the feasibility of high-contrast, low-power frequency-selective electro-optic nanocavity modulators in graphene-integrated silicon photonic chips.