Graphene waveguide-integrated thermal infrared emitter

Low-cost and easily integrable mid-infrared (MIR) sources are highly desired for photonic integrated circuits. Thermal incandescent MIR sources are widely used. They work by Joule heating, i.e. an electrical current through the emitter causes thermal emission according to Planck's law. Their simple design with only two contact pads makes them integrable with typical optoelectronic components in high-volume production flows. Graphene's emissivity is comparable to common metallic emitters. In contrast to the latter, graphene is transparent at MIR wavelengths, which enables placing large area graphene emitters in the evanescent field of integrated waveguides [1]–[2]. This enhances emission by near-field coupling directly into the waveguide mode, avoiding the mode-mismatch to free space. Here, we present the first experimental demonstration of a graphene emitter placed directly on a photonic waveguide, hence emitting directly into the waveguide mode.