Embodiments herein describe a photonic device that includes a germanium photodetector coupled to multiple silicon waveguides. In one embodiment, the silicon waveguides optically couple to a layer of germanium material. In one embodiment, if the germanium material forms a polygon, then a respective silicon waveguide optically couple to each of the corners of the polygon. Each of the plurality of input silicon waveguides may be arranged to transmit light in a direction under the germanium that is offset relative to both sides of the germanium forming the respective corner. In another example, the germanium material may be a circle or ellipse in which case the silicon waveguides terminate at or close to a non-straight, curved surface of the germanium material. As described below, optically coupling the silicon waveguides at a non-straight surface can reduce the distance charge carriers have to travel in the optical detector which can improve bandwidth.