Mode-field Matching Down-Tapers on Single-Mode Optical Fibers for Edge Coupling Towards Generic Photonic Integrated Circuit Platforms

Connections between standard single-mode fibers and waveguides in photonic integrated circuits tend to have relatively high coupling losses due to a difference in mode size and mode profile between both light guiding media. Edge coupling strategies involving specialty fibers are frequently used to o...

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Bibliographic Details
Published in:Journal of lightwave technology 2020-09, Vol.38 (17), p.4834-4842
Main Authors: Vanmol, Koen, Saurav, Kumar, Panapakkam, Vivek, Thienpont, Hugo, Vermeulen, Nathalie, Watte, Jan, Van Erps, Jurgen
Format: Article
Language:English
Subjects:
3D direct laser writing
Coupling
Couplings
Direct laser writing
Efficiency
fiber taper
fiber-to-chip coupling
generic platforms
Integrated circuits
Integrated optics
mode-matching
Optical coupling
Optical device fabrication
Optical fibers
optical interconnects
Optical waveguides
Phosphides
photonic integrated circuits
Photonics
Platforms
Silicon nitride
Tapering
two-photon polymerization
Waveguides
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Summary:Connections between standard single-mode fibers and waveguides in photonic integrated circuits tend to have relatively high coupling losses due to a difference in mode size and mode profile between both light guiding media. Edge coupling strategies involving specialty fibers are frequently used to obtain the best performance in terms of coupling efficiency, bandwidth and polarization independence. We propose the fabrication of free-standing down-taper structures on top of cleaved fiber facets by two-photon direct laser writing and show their performance for silicon, silicon nitride and indium phosphide generic chip platforms. We present a comprehensive analysis of the design of such taper structures that show unprecedented flexibility. We demonstrate their fabrication and fully characterize them in terms of output modal fields and coupling efficiencies. Furthermore, we experimentally compare the fabricated down-tapers with commercially available lensed fibers and demonstrate equal or better coupling efficiency for four out of the five investigated photonic integrated circuit platforms, with a measured improvement in coupling efficiency up to 1.43 dB.
ISSN:0733-8724
1558-2213
DOI:10.1109/JLT.2020.2997090