A polarization-independent refracting-facet uni-traveling-carrier photodiode with high efficiency and large bandwidth

A polarization-independent high-efficiency edge-illuminated refracting-facet photodiode (RFPD) with a uni-traveling-carrier (UTC) structure has been developed. The efficiency is maximized by using a ring-shaped electrode, and the polarization dependence is minimized by designing the layers so that the interferences between the lights reflected from the different interfaces compensate each other. The fabricated RF-UTC-PD shows a responsivity as high as 1.0 A/W with a polarization dependence of less than 0.2 dB. A large 3-dB bandwidth of over 50 GHz at a high operation current of 20 mA is also observed.