Gbps Waveguide Photodiodes

*System Devices Research Laboratories †System Platforms Research Laboratories Two types of waveguide photodiodes (WG-PD)  an evanescently coupled photodiode (EC-WG-PD) and a separated-absorption-and-multiplication avalanche photodiode (WG-APD)  were developed for use in 40Gbps receivers. The EC-WG-PD is much more robust than a conventional WG-PD under high optical input operation because of its distributed absorbed optical power density along the light propagation in the waveguide. The EC-WG-PD simultaneously exhibited a high external quantum efficiency of 70% for both 1,310 and 1,550nm, a wide bandwidth of >40GHz, and as high as 10mA photocurrent operation. The WG-APD, on the other hand, has a wide bandwidth of 35GHz and a gain-bandwidth product of 140GHz as a result of its small waveguide mesa structure and a thin multiplication layer. Record high receiver sensitivities of −19.6dBm at 40Gbps were achieved.