Millimeter-wave opto-electronic devices based on waveguide photodiodes

Recent developments in high-speed photodetectors show a trend toward high e fficiency and high output voltage. The waveguide photodiode is a powerful t ool for achieving both the objectives - it has a bandwidth of more than 100 GHz and an efficiency of 50%. The recently developed uni-traveling-carrier structure has boosted the output voltage of the waveguide photodiode up to 1.3 V, which is high enough for directly operating a digital circuit. Anot her trend is toward reducing the receiver cost. As opto-electronics-integra ted-circuit technology based on the waveguide photodiode becomes mature and its speed reaches the 40-GHz region, it will play an important role in con structing future high-speed systems at low cost.