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  • Open Access

Spectral Dynamics in Broadband Frequency Combs with Overlapping Harmonics

Weichen Fan1, Furkan Ayhan2, Thibault Wildi1, Mikhail Volkov3, Ali Seer3, Markus Ludwig1,†, Thibault Voumard1,‡, Andreas Brodschelm3, Victor Brasch4 et al.

Luis Guillermo Villanueva2 and Tobias Herr1,5,*

  • *Contact author: tobias.herr@desy.de
  • †Present address: Université du Luxembourg, L-1511 Luxembourg, Luxembourg.
  • ‡Present address: Swiss Center for Electronics and Microtechnology (CSEM), 2000 Neuchâtel, Switzerland.
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Phys. Rev. Lett. 135, 213801 – Published 21 November, 2025

DOI: https://doi.org/10.1103/kgd7-52hy

Abstract

Optical frequency combs and their spectra of evenly spaced discrete laser lines are essential to modern time and frequency metrology. Recent advances in integrated photonic waveguides enable efficient nonlinear broadening of an initially narrowband frequency comb to multi-octave bandwidth. Here, we study the nonlinear dynamics in the generation of such ultrabroadband spectra where different harmonics of the comb can overlap. We show that a set of interleaved combs with different offset frequencies extending across the entire spectrum can emerge, which can be arranged into a practically evenly spaced ultrabroadband frequency comb when the initial comb is offset-free.

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Phys. Rev. Lett. 135, 213801– Published 21 November, 2025
  • Received 10 March 2025
  • Accepted 29 September 2025
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