Efficient evanescent wave coupling conditions for waveguide-integrated thin-film Si/Ge photodetectors on silicon-on-insulator/germanium-on-insulator substrates
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Kimerling_Efficient evanescent.pdf
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Author(s)
Ahn, Donghwan
Kimerling, Lionel C.
Michel, Jurgen
Date Issued
October 2011
Journal
Journal of Applied Physics
Publisher
American Institute of Physics (AIP)
Citation
Ahn, Donghwan, Lionel C. Kimerling, and Jurgen Michel. “Efficient evanescent wave coupling conditions for waveguide-integrated thin-film Si∕Ge photodetectors on silicon-on-insulator∕germanium-on-insulator substrates.” Journal of Applied Physics 110, no. 8 (2011): 083115. © 2011 American Institute of Physics
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Final published version
Abstract
We studied evanescent wave coupling behavior between low index-contrast upper-level waveguides and thin-film Si and Ge photodetectors on SOI and germanium-on-insulator (GOI) substrates, respectively. We present a simple and intuitive leaky-mode phase-matching model using a ray-optics approach to determine the conditions for efficient coupling, both in 2D and 3D structures. It is shown that the presence of leaky modes that are phase-matched between the waveguide and the Si or Ge photodetector layer is the key condition for efficient coupling. Our approach was compared to other methods, such as finite-difference time domain (FDTD)/beam propagation method (BPM) and mode analysis. We report that, depending on the way a waveguide photodetector device is designed, waveguide-to-photodetector coupling efficiency may or may not be critically sensitive to design parameters, such as the photodetector layer thickness. As an example, the stark contrast of coupling behavior in the two most popular Ge photodetector structures integrated with Si rib waveguide versus channel waveguide is shown. The device design factors and the trends that affect such coupling sensitivity are identified and explained in the paper.
MIT Department
MIT Materials Research Laboratory
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1063/1.3642943
