Cavity Enhanced Light-Matter Interaction in a Graphene Photodetector

Resonant cavities, confining light in sub-wavelength dimensions are key elements of the rapid advance in the development of on-chip optoelectronic devices. Recently, graphene has been studied for its physical and device properties, revealing fascinating properties for ultrafast and compact communication systems [1]. However, the response cannot compete with state-of-the art technology. Here, we present a detector concept combining a resonant cavity together with graphene as shown in Fig 1(a). The constructive interference inside the ring gives rise to an absorption of the guided light near unity. Dual-gate electrodes centred on top of the active layer allows to generate a pn-junction in the graphene layer, optimizing the response due to the photo-thermoelectric (PTE) effect [2]. The remarkable strong light-matter interaction results in an elevated temperature of the photo-excited carriers of several hundreds of Kelvin, depending on the input power as the data in Fig 1(b) shows. Thus, showing a nonlinear behaviour of the carrier temperature as suggested in the supercollision model [3]. The detector reaches a record high responsivity fore PTE-based detectors of 28 V/W and an electrical 3dB cut-off frequency of 10 GHz.