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Proceedings Paper

VTT's micron-scale silicon rib+strip waveguide platform
Author(s): Timo Aalto; Mikko Harjanne; Matteo Cherchi
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Paper Abstract

Silicon rib waveguides enable single-mode (SM) operation even with the combination of multi-micron core dimensions and high refractive index contrast. In such large waveguides the optical mode field is almost completely confined inside the Si core, which leads to small propagation losses and small polarization dependency. The unique SM condition of the rib waveguide also enables the use of an ultra-wide wavelength range, for example from 1.2 to <1.7 μm, without sacrificing either SM operation or low propagation loss. This makes micron-scale Si waveguides particularly well-suited for spectroscopy and extensive wavelength division multiplexing. However, rib waveguides require large bending radii, which lead to large circuit sizes. There are two solutions for this. So-called Euler bends in Si strip waveguides enable low-loss bends down to 1 μm bending radius with less than 0.1 dB/90° loss for both polarizations. Another alternative is a total-internal reflection mirror that can have loss as low as 0.1 dB for both polarizations in either strip or rib waveguides. The excitation of higher order modes in large strip waveguides is avoided by using adiabatic rib-strip converters and low-loss components. With rib and strip waveguides it is possible to reach a unique combination of low loss, extremely small footprint, small polarization dependency, ultra-wide bandwidth and tolerance to high optical powers.

Paper Details

Date Published: 13 May 2016
PDF: 8 pages
Proc. SPIE 9891, Silicon Photonics and Photonic Integrated Circuits V, 98911G (13 May 2016); doi: 10.1117/12.2234588
Show Author Affiliations
Timo Aalto, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Mikko Harjanne, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Matteo Cherchi, VTT Technical Research Ctr. of Finland Ltd. (Finland)


Published in SPIE Proceedings Vol. 9891:
Silicon Photonics and Photonic Integrated Circuits V
Laurent Vivien; Lorenzo Pavesi; Stefano Pelli, Editor(s)

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