Photodetector with a multimode interference region, high angled photodiodes and refractive-index-modifying regions

A waveguide photodetector comprising:

• a multimode waveguide region;
• an input port at a first side of the multimode waveguide region;
• a plurality of output ports at a second side of the multimode waveguide region, the second side opposite the first side;
• a main waveguide;
• and
• for each output port:
• an absorbing waveguide integrated with the main waveguide, the absorbing waveguide having an optical axis;
• an n-doped semiconductor region along a respective first side of the absorbing waveguide;
• a p-doped semiconductor region along a respective second side of the absorbing waveguide, the respective second side opposite the respective first side;
• an input facet at the absorbing waveguide, the input facet forming an acute angle with the optical axis, and an interior of the input facet angled towards the p-doped semiconductor region or the n-doped semiconductor region, such that at least a portion of light impinging on the input facet is refracted towards the p-doped semiconductor region or the n-doped semiconductor region;
• and
• a refractive-index-modifying region located adjacent to the input facet, the refractive-index-modifying region comprising a region of changed refractive index relative to the main waveguide, the refractive-index-modifying region configured to reflect respective light incident thereon toward the input facet.