High-directionality L-shaped fiber-chip grating couplers realized in 300-mm silicon-on-insulator platform with deep-ultraviolet lithography (conference presentation)

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1117/12.2290584
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EditorSearch for: García-Blanco, Sonia M.; Search for: Cheben, Pavel1 
Name affiliation
  1. National Research Council Canada. Advanced Electronics and Photonics
FormatText
TypeAddress
Proceedings titleIntegrated Optics: Devices, Materials, and Technologies XXII
Series titleProceedings of SPIE; no. 10535
ConferenceIntegrated Optics: Devices, Materials, and Technologies XXII, Jan. 27 - Feb. 1, 2018, San Francisco, United States
ISSN0277-786X
1996-756X
ISBN9781510615557
9781510615564
Abstract
Fiber-chip grating couplers providing high-efficiency, robustness and cost-effectivity are recognized as a key building block for large-volume photonic applications. However, the efficiency of silicon-on-insulator (SOI) grating couplers is limited by the mismatch between the beam diffracted by the grating and the fiber mode, back-reflections at the grating-to-waveguide interface, and the power radiated towards the substrate. While the first two limitations can be overcome by grating apodization, the limited diffraction efficiency (directionality) towards the fiber remains a challenge. Typically, grating directionality is optimized by backside metallization, distributed Bragg mirrors, multi-level grating architectures or non-standard etching depths. However, these approaches yield comparatively complex structures, which in turn, come with the expense of extra fabrication costs, hindering the mass-scale development. Alternatively, the blazing effect has been exploited to provide remarkably high directionalities, relying on standard deep and shallow etch depths. Here, we report on the first experimental demonstration of an ultra-directional L-shaped fiber-chip grating coupler fabricated on 300 mm SOI wafer using 193-nm deep-ultraviolet lithography. The grating coupler is realized on a 300-nm-thick Si layer, combining standard full (300 nm) and shallow (150 nm) etch steps in an L-shaped arrangement. This approach yields a remarkably high grating directionality up to 98%. A single-step subwavelength-engineered transition provides an eight-fold reduction of the reflectivity, from ~8% to ~1%. We experimentally demonstrate a coupling efficiency of -2.7 dB, with a 3-dB bandwidth of 62 nm. These results open a new route towards exploiting the blazing effect for the large-volume realization of high-efficiency fiber-chip grating couplers in the low-cost 300 mm SOI photonic platform.
Publication date
PublisherSPIE
LanguageEnglish
Peer reviewedYes
NPARC number23002887
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Record modified2019-07-22
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