Real-time high-resolution heterodyne-based measurements of spectral dynamics in fibre lasers

Srikanth Sugavanam, Simon Fabbri, Son Thai Le, Ivan Lobach, Sergey Kablukov, Serge Khorev, Dmitry Churkin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Conventional tools for measurement of laser spectra (e.g. optical spectrum analysers) capture data averaged over a considerable time period. However, the generation spectrum of many laser types may involve spectral dynamics whose relatively fast time scale is determined by their cavity round trip period, calling for instrumentation featuring both high temporal and spectral resolution. Such real-time spectral characterisation becomes particularly challenging if the laser pulses are long, or they have continuous or quasi-continuous wave radiation components. Here we combine optical heterodyning with a technique of spatiooral intensity measurements that allows the characterisation of such complex sources. Fast, round-trip-resolved spectral dynamics of cavity-based systems in real-time are obtained, with temporal resolution of one cavity round trip and frequency resolution defined by its inverse (85 ns and 24 MHz respectively are demonstrated). We also show how under certain conditions for quasi-continuous wave sources, the spectral resolution could be further increased by a factor of 100 by direct extraction of phase information from the heterodyned dynamics or by using double time scales within the spectrogram approach.

Original languageEnglish
Article number23152
Number of pages8
JournalScientific Reports
Publication statusPublished - 17 Mar 2016

Bibliographical note

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Funding: ERC (project UltraLaser); Horizon 2020 project CARDIALLY; Russian Ministry of Education and Science (14.584.21.0014); Russian Foundation for Basic Research (15-02-07925, 16-32-60153, 14-42-08026 and 14-02-00449А).

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