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Proceedings Paper

High rejection ratio silicon membrane Bragg filters (Conference Presentation)
Author(s): Carlos A. Alonso-Ramos; Xavier Le Roux; Daniel Benedikovic; Vladyslav Vakarin; Elena Durán-Valdeiglesias; Dorian Oser; Diego Pérez-Galacho; Florent Mazeas; Sébastien Tanzilli; Laurent Labonte; Eric Cassan; Delphine Marris-Morini; Pavel Cheben; Laurent Vivien

Paper Abstract

Silicon photonics is considered an enabling technology for next generation datacom applications, providing ultra-compact and high-bandwidth transceivers that are cost-effectively fabricated at the existing CMOS facilities. Among photonic devices developed in silicon, Bragg gratings are routinely used for the realization of key functionalities including wavelength filtering, dispersion engineering and sensing. However, the realization of Bragg filters that simultaneously provides narrowband operation and high rejection remains a challenge in the Si platform. Indeed, the small core size of Si wires, together with the high index contrast between the silicon and the oxide cladding results in a strong interaction of the optical mode with the Bragg structure. Several approaches have been proposed to implement narrowband Bragg filters in Si wires including ultra-small corrugations (a few nanometres), periodic claddings, sub-wavelength engineering or inter-mode coupling. Nevertheless, these filters typically have comparatively weak light rejection performance due to fabrication errors limiting the accurate control of the grating geometry over few millimeter-long waveguide structures. In this work, we present a novel waveguide Bragg grating geometry that leverages the large index contrast between Si and air in membrane waveguides to overcome these limitations, yielding both narrow bandwidth and high rejection ratio. We use a novel waveguide corrugation geometry that radiates out the higher order modes, allowing effective single-mode operation for micrometric fully etched membrane waveguides. The high mode confinement of these waveguides results in weak interaction with the sidewall corrugation, thus narrowband operation is achieved. On the other hand, the high rejection ratio is achieved by combining reflection and radiation effects within the Bragg resonance. Based on this concept, we designed and experimentally demonstrated notch filters in single-etch suspended Si waveguides with cross-sections as large as 0.5 µm (height) by 1.1 µm (width). We show a narrow bandwidth of 4 nm for a 500 nm wide corrugation, with a high rejection ratio exceeding 50 dB for a filter length of only 700 µm

Paper Details

Date Published: 23 May 2018
Proc. SPIE 10671, Metamaterials XI, 106711Z (23 May 2018); doi: 10.1117/12.2307362
Show Author Affiliations
Carlos A. Alonso-Ramos, Ctr. de Nanosciences et de Nanotechnologies (France)
Xavier Le Roux, Ctr. de Nanosciences et de Nanotechnologies (France)
Daniel Benedikovic, Ctr. de Nanosciences et de Nanotechnologies (France)
Vladyslav Vakarin, Ctr. de Nanosciences et de Nanotechnologies (France)
Elena Durán-Valdeiglesias, Ctr. de Nanosciences et de Nanotechnologies (France)
Dorian Oser, Ctr. de Nanosciences et de Nanotechnologies (France)
Diego Pérez-Galacho, Ctr. de Nanosciences et de Nanotechnologies (France)
Univ. Politécnica de Valencia (Spain)
Florent Mazeas, Lab. de Physique de la Matière Condensée (France)
Sébastien Tanzilli, Univ. de Nice Sophia Antipolis (France)
Laurent Labonte, Lab. de Physique de la Matière Condensée (France)
Eric Cassan, Ctr. de Nanosciences et de Nanotechnologies (France)
Delphine Marris-Morini, Ctr. de Nanosciences et de Nanotechnologies (France)
Pavel Cheben, National Research Council Canada (Canada)
Laurent Vivien, Ctr. de Nanosciences et de Nanotechnologies (France)

Published in SPIE Proceedings Vol. 10671:
Metamaterials XI
Allan D. Boardman; Anatoly V. Zayats; Kevin F. MacDonald, Editor(s)

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