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Research at St Andrews

Optical delay beyond the time-bandwidth limit: from pipe dream to reality

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Sebastian A. Schulz, D. Grassani, I. Cardea, S. J. Fabbri, J. Upham, R. W. Boyd, K. L. Tsakmakidis, C.-S. Brès

School/Research organisations


All resonant systems throughout science and engineering, independent of their physical implementation have a bandwidth that is inversely related to the decay time. A similar relation exists in all slow-light systems, where the group index (and therefore the delay for a given footprint) is inversely related to the bandwidth. Therefore, resonant or slow-light systems can either store a broad signal for a short time, or a narrow signal for a long time, but cannot achieve large delay for broad bandwidth signals.Here we discuss our recent work on non-reciprocal optical systems that are not constrained by the delay-bandwidth limit. We show that large, broadband optical delay is not a pipe dream and is achievable with current optical technology. We discuss the underlying physics of delay and bandwidth in non-reciprocal optical systems and present an experimental implementation, based on a figure-9 cavity. We demonstrate a delay-bandwidth product 30 times above the seemingly fundamental time-bandwidth limit of traditional systems. Furthermore, we show that the optical pulse can be released after an arbitrary number of round trips, providing the control and tunability lacking from conventional spiral waveguide or fibre loop delay lines.



Original languageEnglish
Title of host publication21st International Conference on Transparent Optical Networks, ICTON 2019
PublisherIEEE Computer Society
Number of pages4
ISBN (Electronic)9781728127798
Publication statusPublished - 19 Sep 2019
Event21st International Conference on Transparent Optical Networks, ICTON 2019 - Angers, France
Duration: 9 Jul 201913 Jul 2019
Conference number: 21

Publication series

NameInternational Conference on Transparent Optical Networks
ISSN (Electronic)2162-7339


Conference21st International Conference on Transparent Optical Networks, ICTON 2019
Abbreviated titleICTON
Internet address

    Research areas

  • Delay-bandwidth product, Non-reciprocity, Optical fibres

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