High-responsivity and high-speed evanescently-coupled avalanche photodiodes

Evanescently-coupled avalanche photodiodes utilising a planar short multimode waveguide are demonstrated. These devices exhibit high responsivity (>0.62 A/W at unit gain) with polarisation dependence less than 0.5 dB, broad bandwidth (34.8 GHz at low gain) and 160 GHz gain-bandwidth product.