Open Access
31 December 2020 High coupling efficiency, passive alignment setup for visible-range fiber-to-waveguide edge coupling
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Abstract

We present a method to passively edge couple multiple optical fibers with silicon nitride waveguides in the visible wavelengths. We efficiently convert the fiber mode to the waveguide mode using an inverse taper mode size converter and support passive alignment using a U-groove that centers the optical fiber to the inverse taper. In our prototypes, we measure a coupling efficiency of −4.2  dB per facet. To reduce light leakage to the silicon substrate, we use a 6-μm oxide layer, which also eliminates the additional processes of undercutting the silicon substrate underneath the waveguide. Furthermore, the U-groove structure has a polished edge surface for coupling, reducing the steps of edge polishing the die. Fabrication of this visible-range edge coupler is complementary metal–oxide–semiconductor-compatible, making it a highly scalable method for passively packaging multiple visible-range integrated photonics devices.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Nathan C. Lin, Sakib Hassan, Xuan Zhao, Ashok Veeraraghavan, and Jacob T. Robinson "High coupling efficiency, passive alignment setup for visible-range fiber-to-waveguide edge coupling," Journal of Nanophotonics 14(4), 046018 (31 December 2020). https://doi.org/10.1117/1.JNP.14.046018
Received: 7 September 2020; Accepted: 18 December 2020; Published: 31 December 2020
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CITATIONS
Cited by 4 scholarly publications.
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KEYWORDS
Waveguides

Silicon

Fiber couplers

Optical alignment

Etching

Polishing

Visible radiation

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