SOI Waveguide Integrated Graphene Mid-Infrared Detector

Abstract

Mid-infrared group IV photonics is a vibrant field, which aims to migrate techniques used for near-infrared silicon photonics to longer wavelengths in order to build photonic integrated lab-on-a-chip sensors that can be applied in areas such as remote sensing, homeland security, medical diagnostics or environmental monitoring.

In order to create mid-infrared lab-on-a-chip sensors, both passive and active devices are required. Passive deceives for wavelengths up to 4 m can be created using the silicon-on-insulator waveguide platform, which is commonly used in the near-infrared, and is compatible with the standard and developed near-infrared fabrication techniques. Graphene is a 2-D material that has excellent electronic and optical properties. It can interact with light from microwave to ultraviolet wavelengths, making it a potential candidate for light detection applications over a wide spectral range. By taking advantage of the wide transparency range of group IV platforms in the midinfrared and the 2-D nature of graphene, this project is aiming to investigate the integration of graphene mid-infrared photodetectors with silicon waveguides.

In this project, two different designs of SOI waveguide integrated graphene mid-infrared photodetectors have been fabricated and characterised, exhibiting responsivities of 2.2 mA/W at the 3.8 m wavelength, which is the longest wavelength demonstration up date of waveguide integrated graphene photodetection. In addition, these devices exhibited photodetection at wavelengths up to 7.7 m, confirming that graphene is a promising detector candidate for even longer wavelengths.

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