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Proceedings Paper

Silicon nitride back-end optics for biosensor applications
Author(s): Sebastian Romero-García; Florian Merget; Frank C. Zhong; Hod Finkelstein; Jeremy Witzens
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Paper Abstract

Silicon nitride (SiN) is a promising candidate material for becoming a standard high-performance solution for integrated biophotonics applications in the visible spectrum. As a key feature, its compatibility with the complementary-oxidemetal- semiconductor (CMOS) technology permits cost reduction at large manufacturing volumes that is particularly advantageous for manufacturing consumables. In this work, we show that the back-end deposition of a thin SiN film enables the large light-cladding interaction desirable for biosensing applications while the refractive index contrast of the technology (Δn ≈ 0.5) also enables a considerable level of integration with reduced waveguide bend radii. Design and experimental validation also show that several advantages are derived from the moderate SiN/SiO2 refractive index contrast, such as lower scattering losses in interconnection waveguides and relaxed tolerances to fabrication imperfections as compared to higher refractive index contrast material systems. As a drawback, a moderate refractive index contrast also makes the implementation of compact grating couplers more challenging, due to the fact that only a relatively weak scattering strength can be achieved. Thereby, the beam diffracted by the grating tends to be rather large and consequently exhibit stringent angular alignment tolerances. Here, we experimentally demonstrate how a proper design of the bottom and top cladding oxide thicknesses allows reduction of the full-width at half maximum (FWHM) and alleviates this problem. Additionally, the inclusion of a CMOS-compatible AlCu/TiN bottom reflector further decreases the FWHM and increases the coupling efficiency. Finally, we show that focusing grating designs greatly reduce the device footprint without penalizing the device metrics.

Paper Details

Date Published: 7 May 2013
PDF: 11 pages
Proc. SPIE 8781, Integrated Optics: Physics and Simulations, 87810W (7 May 2013); doi: 10.1117/12.2018890
Show Author Affiliations
Sebastian Romero-García, RWTH Aachen (Germany)
Florian Merget, RWTH Aachen (Germany)
Frank C. Zhong, Illumina, Inc. (United States)
Hod Finkelstein, Illumina, Inc. (United States)
Jeremy Witzens, RWTH Aachen (Germany)

Published in SPIE Proceedings Vol. 8781:
Integrated Optics: Physics and Simulations
Pavel Cheben; Jiří Čtyroký; Iñigo Molina-Fernandez, Editor(s)

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