Diplexer with integrated filters and photodetector in Ge-Si using Γ-X and Γ-M directions in a grating coupler

Christopher R. Doerr, Long Chen, Mahmoud S. Rasras, Young Kai Chen, Joseph S. Weiner, Mark P. Earnshaw

Research output: Contribution to journalArticle


We demonstrate a central-office-type diplexer in which the filter and photodetector are monolithically integrated on a silicon-on-insulator substrate. The photonic integrated circuit receives a 1577-nm signal from an external laser and sends it to the fiber link using a two-dimensional grating coupler. The same grating coupler receives a 1270-nm signal from the fiber link and sends it to a monolithically integrated germanium photodetector using a polarization-diversity scheme to achieve polarization independence. The grating coupler is novel in that both the Γ-X and Γ-M directions are employed. This allows the grating coupler to couple both the 1577- and 1270-nm wavelengths with a small fiber tilt angle and hence have low polarization-dependent loss.

Original languageEnglish (US)
Pages (from-to)1698-1700
Number of pages3
JournalIEEE Photonics Technology Letters
Issue number22
StatePublished - Nov 15 2009



  • Germanium
  • Grating
  • Integrated optics
  • Photodetector
  • Photonic crystal
  • Silicon photonics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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