Low-loss delay lines with small footprint on a micron-scale SOI platform

Matteo Cherchi, Mikko Harjanne, Konstantinos Vyrsokinos, Sami Ylinen, Markku Kapulainen, Tapani Vehmas, Timo Aalto

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

    2 Citations (Scopus)


    Long and yet compact spiral waveguides based on micron-scale silicon strip waveguides has been enabled very recently by the introduction of the Euler bends. By ensuring effective broadband single mode operation of otherwise highly multimodal waveguides, these bends can have very low losses (<0.01 dB/90°) even with effective radii of a few microns. Together with the low propagation losses (< 0.15 dB/cm) of micron-scale strip waveguides, these bends enable centimeter-long delay lines with negligible losses and very small foot-print (< 1 mm2). In particular, interferometers delayed by ≈ 1 cm long spirals on one of the two arms have been fabricated on SOI wafers with both 3 um- and 4 umthick silicon layer, based on the well assessed process developed by VTT. The full devices have footprint smaller than 1.5 mm2, and they have been measured to have extinction ratios < 15 dB (reaching up to 21 dB) and about 3 dB excess losses. Functional characterization of the delayed interferometers at about 10 Gbps through demodulation of pseudorandom Differential Phase Shift Keying signals led to clearly opened eye diagrams with Q factor of 8.6 and bit error rates lower than 10-15.
    Original languageEnglish
    Title of host publicationSilicon Photonics X
    EditorsGraham T. Reed, Michael R. Watts
    PublisherInternational Society for Optics and Photonics SPIE
    ISBN (Print)978-1-6284-1457-8
    Publication statusPublished - 27 Feb 2015
    MoE publication typeA4 Article in a conference publication
    EventSilicon Photonics X - San Francisco, United States
    Duration: 9 Feb 201512 Feb 2015

    Publication series

    SeriesProceedings of SPIE


    ConferenceSilicon Photonics X
    Abbreviated titleSPIE OPTO
    Country/TerritoryUnited States
    CitySan Francisco


    • delay lines
    • delayed interferometers
    • DPSK demodulation
    • integrated optics
    • photonic integrated circuits
    • silicon photonics
    • spiral waveguides


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