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Proceedings Paper

Surface normal coupling to multiple-slot and cover-slotted silicon nanocrystalline waveguides and ring resonators
Author(s): John Covey; Ray T. Chen
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Paper Abstract

Grating couplers are ideal for coupling into the tightly confined propagation modes of semiconductor waveguides. In addition, nonlinear optics has benefited from the sub-diffraction limit confinement of horizontal slot waveguides. By combining these two advancements, slot-based nonlinear optics with mode areas less than 0.02 μm2 can become as routine as twisting fiber connectors together. Surface normal fiber alignment to a chip is also highly desirable from time, cost, and manufacturing considerations. To meet these considerable design challenges, a custom genetic algorithm is created which, starting from purely random designs, creates a unique four stage grating coupler for two novel horizontal slot waveguide platforms. For horizontal multiple-slot waveguides filled with silicon nanocrystal, a theoretical fiber-towaveguide coupling efficiency of 68% is obtained. For thin silicon waveguides clad with optically active silicon nanocrystal, known as cover-slot waveguides, a theoretical fiber-to-waveguide coupling efficiency of 47% is obtained, and 1 dB and 3 dB theoretical bandwidths of 70 nm and 150 nm are obtained, respectively. Both waveguide platforms are fabricated from scratch, and their respective on-chip grating couplers are experimentally measured from a standard single mode fiber array that is mounted surface normally. The horizontal multiple-slot grating coupler achieved an experimental 60% coupling efficiency, and the horizontal cover-slot grating coupler achieved an experimental 38.7% coupling efficiency, with an extrapolated 1 dB bandwidth of 66 nm. This report demonstrates the promise of genetic algorithm-based design by reducing to practice the first large bandwidth vertical grating coupler to a novel silicon nanocrystal horizontal cover-slot waveguide.

Paper Details

Date Published: 8 March 2014
PDF: 13 pages
Proc. SPIE 8991, Optical Interconnects XIV, 89911A (8 March 2014); doi: 10.1117/12.2044231
Show Author Affiliations
John Covey, The Univ. of Texas at Austin (United States)
Ray T. Chen, The Univ. of Texas at Austin (United States)

Published in SPIE Proceedings Vol. 8991:
Optical Interconnects XIV
Henning Schröder; Ray T. Chen; Alexei L. Glebov, Editor(s)

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