Open AccessMonolithic integration and synchronous operation of germanium photodetectors and silicon variable optical attenuators
Author(s) -
Sungbong Park,
Tai Tsuchizawa,
T. Watanabe,
Hiroyuki Satō,
Hidetaka Nishi,
Koji Yamada,
Yasuhiko Ishikawa,
Kazumi Wada,
S. Itabashi
Publication year - 2010
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.18.008412
Subject(s) - responsivity , photodetector , materials science , optoelectronics , optics , optical attenuator , attenuator (electronics) , germanium , waveguide , optical power , dark current , silicon , optical communication , optical modulator , attenuation , optical fiber , phase modulation , physics , multi mode optical fiber , laser , phase noise
We demonstrate the monolithic integration of germanium (Ge) p-i-n photodetector (PDs) with silicon (Si) variable optical attenuator (VOAs) based on submicrometer Si rib waveguide. A PD is connected to a VOA along the waveguide via a tap coupler. The PDs exhibit low dark current of ~60 nA and large responsivity of ~0.8 A/W at the reverse bias of 1 V at room temperature. These characteristics are uniform over the chip scale. The PDs generate photocurrents precisely with respect to DC optical power attenuated by the VOAs. Two devices work synchronously for modulated optical signals as well. 3-dB cut-off frequency of the VOA is ~100 MHz, while that of the PD is ~1 GHz. The synchronous response speed is limited by the VOA response speed. This is the first demonstration, to the best of our knowledge, of monolithic integration of Ge PDs with high-carrier-injection-based optical modulation devices based on Si.