Graphene thermal infrared emitters integrated into silicon photonic waveguides

TL;DR

This paper demonstrates graphene-based mid-infrared emitters integrated with silicon photonic waveguides, achieving high coupling efficiency and broadband emission suitable for applications like CO2 sensing.

Contribution

It introduces a novel graphene mid-IR emitter integrated into silicon waveguides with high coupling efficiency and broadband emission, advancing photonic integrated circuit applications.

Findings

Achieved up to 68% coupling efficiency into waveguides.

Observed high broadband emission intensity at 4.2 μm.

Predicted emitter temperatures up to 1000°C for blackbody radiation.

Abstract

Cost-efficient and easily integrable broadband mid-infrared (mid-IR) sources would significantly enhance the application space of photonic integrated circuits (PICs). Thermal incandescent sources are superior to other common mid-IR emitters based on semiconductor materials in terms of PIC compatibility, manufacturing costs, and bandwidth. Ideal thermal emitters would radiate directly into the desired modes of the PIC waveguides via near-field coupling and would be stable at very high temperatures. Graphene is a semi-metallic two-dimensional material with comparable emissivity to thin metallic thermal emitters. It allows maximum coupling into waveguides by placing it directly into their evanescent fields. Here, we demonstrate graphene mid-IR emitters integrated with photonic waveguides that couple directly into the fundamental mode of silicon waveguides designed for a wavelength of 4,2 {\mu}m relevant for CO${_2}$ sensing. High broadband emission intensity is observed at the waveguide-integrated graphene emitter. The emission at the output grating couplers confirms successful coupling into the waveguide mode. Thermal simulations predict emitter temperatures up to 1000{\deg}C, where the blackbody radiation covers the mid-IR region. A coupling efficiency {\eta}, defined as the light emitted into the waveguide divided by the total emission, of up to 68% is estimated, superior to data published for other waveguide-integrated emitters.