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Recent Advances in Ultra-High-Speed Waveguide Photodiodes for Optical Communication Systems
IEICE TRANSACTIONS on Electronics Vol.E92-C No.7 pp.922-928
Publication Date: 2009/07/01
Online ISSN: 1745-1353
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Advances in Ultra-high-speed Photonic Devices for Next-generation Optical Fiber Communications)
PIN photodiode (PIN-PD),
avalanche photodiode (APD),
evanescently coupled photodiode,
differential phase shift-keying (DPSK),
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This paper describes the recent advances in semiconductor photodiodes for use in ultra-high-speed optical systems. We developed two types of waveguide photodiodes (WG-PD) -- an evanescently coupled waveguide photodiode (EC-WG-PD) and a separated-absorption-and-multiplication waveguide avalanche photodiode (WG-APD). The EC-WG-PD is very robust under high optical input operation because of its distribution of photo current density along the light propagation. The EC-WG-PD simultaneously exhibited a high external quantum efficiency of 70% for both 1310 and 1550 nm, and a wide bandwidth of more than 40 GHz. The WG-APD, on the other hand, has a wide bandwidth of 36.5 GHz and a gain-bandwidth product of 170 GHz as a result of its small waveguide mesa structure and a thin multiplication layer. Record high receiver sensitivity of -19.6 dBm at 40 Gbps was achieved. Additionally, a monolithically integrated dual EC-WG-PD for differential phase shift-keying (DPSK) systems was developed. Each PD has equivalent characteristics with 3-dB-down bandwidth of more than 40 GHz and external quantum efficiency of 70% at 1550 nm.