Flat-top MZI filters: A novel robust design based on MMI splitters

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

2 Citations (Scopus)

Abstract

Multimode Interferometers (MMIs) are an attractive alternative to directional couplers, ensuring more relaxed tolerances to fabrication errors and broader operation bandwidth. The drawback is that only a limited discrete set of splitting ratios is achievable with MMIs of constant cross section. This issue clearly limits their use in flat-top interferometric filters, which design requires, in general, free choice of the splitting ratios. Here we show for the first time that it is possible to design 4-stage flat-top interferometers using only standard MMIs with 50:50 and 85:15 splitting ratios. The design approach is based on the representation of the system on the Bloch sphere. Flat-top interleavers with different free spectral ranges have been designed and fabricated on the silicon photonics platform of VTT, based on 3 μm thick rib and strip waveguides. Two different layouts have been explored: one where all components are collinear and a more compact one which elements have been folded in a spiral shape. All interleavers have been designed for TE polarization, and they work in a wavelength range comparable with the 100 nm bandwidth of the MMI splitters. Even though fabrication imperfections and non-ideal behaviour of both waveguide bends and MMIs led to reduced extinction compared to simulations, most devices show in-band extinction exceeding 15 dB. The in-band losses of the most central channels did not exceed 1.5 dB compared to the reference straight waveguide. The designed interleavers can be employed in cascaded configurations to achieve broadband and fabrication tolerant flat-top wavelength (de)multiplexers.

Original languageEnglish
Title of host publicationSilicon Photonics XI
PublisherInternational Society for Optics and Photonics SPIE
ISBN (Electronic)9781628419870
ISBN (Print)978-1-6284-1987-0
DOIs
Publication statusPublished - 1 Jan 2016
MoE publication typeA4 Article in a conference publication
EventSilicon Photonics XI - San Francisco, United States
Duration: 15 Feb 201617 Feb 2016

Publication series

SeriesProceedings of SPIE
Volume9752
ISSN0277-786X

Conference

ConferenceSilicon Photonics XI
CountryUnited States
CitySan Francisco
Period15/02/1617/02/16

Fingerprint

Robust Design
Interferometer
Interferometers
interferometers
Filter
filters
Waveguide
Fabrication
Waveguides
waveguides
Extinction
fabrication
extinction
Bandwidth
Wavelength
bandwidth
Silicon Photonics
Light extinction
Directional couplers
Filter Design

Keywords

  • Photonic Integrated Circuits, Integrated Optics, Silicon Photonics, WDM filters, Multimode interference splitters

Cite this

Cherchi, M., Harjanne, M., Ylinen, S., Kapulainen, M., Vehmas, T., & Aalto, T. (2016). Flat-top MZI filters: A novel robust design based on MMI splitters. In Silicon Photonics XI [975210] International Society for Optics and Photonics SPIE. Proceedings of SPIE, Vol.. 9752 https://doi.org/10.1117/12.2210937
Cherchi, Matteo ; Harjanne, Mikko ; Ylinen, Sami ; Kapulainen, Markku ; Vehmas, Tapani ; Aalto, Timo. / Flat-top MZI filters : A novel robust design based on MMI splitters. Silicon Photonics XI. International Society for Optics and Photonics SPIE, 2016. (Proceedings of SPIE, Vol. 9752).
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Cherchi, M, Harjanne, M, Ylinen, S, Kapulainen, M, Vehmas, T & Aalto, T 2016, Flat-top MZI filters: A novel robust design based on MMI splitters. in Silicon Photonics XI., 975210, International Society for Optics and Photonics SPIE, Proceedings of SPIE, vol. 9752, Silicon Photonics XI, San Francisco, United States, 15/02/16. https://doi.org/10.1117/12.2210937

Flat-top MZI filters : A novel robust design based on MMI splitters. / Cherchi, Matteo; Harjanne, Mikko; Ylinen, Sami; Kapulainen, Markku; Vehmas, Tapani; Aalto, Timo.

Silicon Photonics XI. International Society for Optics and Photonics SPIE, 2016. 975210 (Proceedings of SPIE, Vol. 9752).

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

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N2 - Multimode Interferometers (MMIs) are an attractive alternative to directional couplers, ensuring more relaxed tolerances to fabrication errors and broader operation bandwidth. The drawback is that only a limited discrete set of splitting ratios is achievable with MMIs of constant cross section. This issue clearly limits their use in flat-top interferometric filters, which design requires, in general, free choice of the splitting ratios. Here we show for the first time that it is possible to design 4-stage flat-top interferometers using only standard MMIs with 50:50 and 85:15 splitting ratios. The design approach is based on the representation of the system on the Bloch sphere. Flat-top interleavers with different free spectral ranges have been designed and fabricated on the silicon photonics platform of VTT, based on 3 μm thick rib and strip waveguides. Two different layouts have been explored: one where all components are collinear and a more compact one which elements have been folded in a spiral shape. All interleavers have been designed for TE polarization, and they work in a wavelength range comparable with the 100 nm bandwidth of the MMI splitters. Even though fabrication imperfections and non-ideal behaviour of both waveguide bends and MMIs led to reduced extinction compared to simulations, most devices show in-band extinction exceeding 15 dB. The in-band losses of the most central channels did not exceed 1.5 dB compared to the reference straight waveguide. The designed interleavers can be employed in cascaded configurations to achieve broadband and fabrication tolerant flat-top wavelength (de)multiplexers.

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KW - Photonic Integrated Circuits, Integrated Optics, Silicon Photonics, WDM filters, Multimode interference splitters

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Cherchi M, Harjanne M, Ylinen S, Kapulainen M, Vehmas T, Aalto T. Flat-top MZI filters: A novel robust design based on MMI splitters. In Silicon Photonics XI. International Society for Optics and Photonics SPIE. 2016. 975210. (Proceedings of SPIE, Vol. 9752). https://doi.org/10.1117/12.2210937