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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 14, Iss. 11 — May. 29, 2006
  • pp: 4695–4702

Subwavelength waveguide grating for mode conversion and light coupling in integrated optics

P. Cheben, D-X. Xu, S. Janz, and A. Densmore  »View Author Affiliations

Optics Express, Vol. 14, Issue 11, pp. 4695-4702 (2006)

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We propose a new method for mode conversion and coupling between an optical fiber and a sub-micrometer waveguide using a subwavelength grating (SWG) with a period less than the 1st order Bragg period. The coupler principle is based on gradual modification of the waveguide mode effective index by the SWG effect that at the same time frustrates diffraction and minimizes reflection loss. We demonstrate the proposed principle by two-dimensional Finite Difference Time Domain (FDTD) calculations of various SWG structures designed for the silicon-on-insulator (SOI) platform with a Si core thickness of 0.3 µm. We found a coupling loss as small as 0.9 dB for a 50 µm-long SWG device and low excess loss due to fiber misalignment, namely 0.07 dB for a transverse misalignment of ±1 µm, and 0.24 dB for an angular misalignment of ±2 degrees. Scaling of the SWG coupler length down to 10 µm is also reported on an example of a 2D slab waveguide coupling structure including aspect ratio dependent etching and micro-loading effects. Finally, advantages of the proposed coupling principle for fabricating 3D coupling structures are discussed.

© 2006 Optical Society of America

OCIS Codes
(050.0050) Diffraction and gratings : Diffraction and gratings
(130.1750) Integrated optics : Components
(130.3120) Integrated optics : Integrated optics devices
(230.7380) Optical devices : Waveguides, channeled
(230.7390) Optical devices : Waveguides, planar
(250.5300) Optoelectronics : Photonic integrated circuits

ToC Category:
Integrated Optics

Original Manuscript: April 11, 2006
Revised Manuscript: May 15, 2006
Manuscript Accepted: May 16, 2006
Published: May 29, 2006

P. Cheben, D-X. Xu, S. Janz, and A. Densmore, "Subwavelength waveguide grating for mode conversion and light coupling in integrated optics," Opt. Express 14, 4695-4702 (2006)

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