1. Max-Planck-Institut für die Physik des Lichts
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  4. Birgit Stiller

Prof. Dr. Birgit Stiller

Professor

My fields of expertise are Brillouin scattering and optomechanics, nonlinear fiber optics and photonic circuits, as well as classical and quantum communications. The projects in my group span from nonlinear optics to quantum optics with a focus on light-sound interactions and waveguide optomechanics. We want to explore optoacoustic interaction experimentally at the classical and quantum level with suitably engineered microstructured fibres and nanowaveguides to manipulate, in this way, light states

2026

Higher-order exceptional points in a multimode continuum optoacoustic system

Anton Montag, Julius Gohsrich, Quentin Levoy, Birgit Stiller, Flore K. Kunst

arXiv 2606.04671 (2026) | Preprint | PDF

Exceptional points appear in non-Hermitian systems as degeneracies, where not only eigenvalues but also eigenvectors coalesce. They are of great theoretical and experimental interest due to their exotic topological properties and enhanced sensitivity to perturbations. Experimental realizations of higher-order exceptional points, where more than two eigenvectors coalesce, rely on highly fine-tuned setups. Recently, stimulated Brillouin scattering has been employed to generate second-order exceptional points in a fabrication-free setup by leveraging off-resonant scattering. In this work we generalize this approach, and we develop an off-resonant, multimode theory for stimulated Brillouin scattering as an avenue towards realizing symmetry-induced exceptional points of any order. We present the experimental implementation of our program in an accompanying paper. Our multimode theory could also be employed in applications in optoacoustic sensing, synthetic neuromorphic computing, microwave photonic filters, and optoacoustic quantum signal processing.

Multi-dimensional parameter space of higher-order exceptional points induced by Brillouin optoacoustics

Grigorii Slinkov, Anton Montag, Julius Gohsrich, Quentin Levoy, Paulina Fuentes Rivera, Flore K. Kunst, Birgit Stiller

arXiv 2606.05064 (2026) | Preprint | PDF

Exceptional points (EPs) are degeneracies in the spectrum of non-Hermitian systems, where both the eigenvalues and eigenvectors coalesce. In the vicinity of an n-th order EP, the eigenvalues generally show n-th-root dependence on the system parameters, making EPs potentially promising candidates for ultra-sensitive measurements. Usually EPs are implemented in precisely fabricated nano- and microstructures. In this work, we instead show the experimental implementation of a third-order EP (EP3) using the synthetic dimension in a single-mode optical fiber, leveraging multi-frequency Brillouin scattering. We perform a multi-dimensional scan of the parameter space revealing not only an EP3 but also additional topological structures connected to it. Our work paves the way toward fabrication-free realizations of exceptional points of arbitrary order.

Brillouin–Mandelstam scattering-based cooling of traveling acoustic waves from cryogenic temperatures

Lisa Fischer, Laura Blázquez Martínez, Changlong Zhu, Robin Chenevière, Johann Troles, Birgit Stiller

Optics Letters 51 121-124 (2026) | Journal | PDF

Thermal phonons are a major source of decoherence in quantum mechanical systems. Operating in the quantum ground state is therefore often an experimental prerequisite. In addition to passive cooling in a cryogenic environment, active laser cooling enables the reduction of phonons at specific acoustic frequencies. Brillouin cooling has been used to show efficient reduction of the thermal phonon population in waveguides at GHz frequencies down to 74 K. In this Letter, we demonstrate the cooling of a 7.608 GHz acoustic mode by combining Brillouin active cooling with precooling from 77 K using liquid nitrogen. We show a 69% reduction in the phonon population, resulting in a final temperature of 24.3 +/- 1.9 K, 50 K lower than previously reported.

Scientific career

  • since 2024 also W3 Full Professorship at Leibniz University Hannover
  • 04/2019 – Independent Max Planck Research Group Leader (centrally funded, selected in the competitive call 2017), Max Planck Institute for the Science of Light, Germany, Quantum Optoacoustic
  • 04/2021- 09/2022 Temporary W3 Full Professorship (Lehrstuhlvertretung), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Chair of Optics
  • 06/2015 – 02/2019 Research fellow, The University of Sydney, CUDOS, Australia, Nonlinear Optical Phononics (Prof. Benjamin Eggleton)
  • 10/2012 – 05/2015 Postdoctoral fellow, Max Planck Institute for the Science of Light, Germany, Optical Communication and Quantum Communication (Prof. Gerd Leuchs)
  • 02/2012 – 09/2012Postdoctoral fellow, CNRS Institute FEMTO-ST, Besançon, France, Nonlinear Optics and Optoacoustics (Dr. Thibaut Sylvestre)

 

Academic education

  • 01/2009 – 01/2012 Doctoral thesis, CNRS Institute FEMTO-ST, Besançon, France, “Brillouin scattering in photonic crystal fibre: from fundamentals to fibre optic sensors”, (Dr. Thibaut Sylvestre, Dr. Hervé Maillotte)
  • 10/2003 – 12/2008 Master’s degree Mathematics / Physics / Education, University of Erlangen-Nuremberg, Germany, Master thesis: „Fabrication of periodically poled LiNbO3 for nonlinear optical frequency conversion by quasi phase matching“ (Prof. Jan-Peter Meyn, Prof. Christine Silberhorn)

 

Selected awards, fellowships, services

  • 2024 - ERC Consolidator Grant
  • 2024 - Henriette Hertz Scout of the Humbold Foundation
  • 2024 - Photonics100 2025 List
  • 2022 Conference chair, Lorentz Workshop “Quantum Optics meets Acoustics”, Leiden, Netherlands (14-18 November 2021)
  • 2020 Editorial board New Journal of Physics
  • 2020 Fellow of the Max Planck School of Photonics
  • 2019-2021 Conference chair, “Workshop on Optomechanics and Brillouin scattering - WOMBAT 2021/2022”, Erlangen, Germany (16-18 June 2021 and 14-17 June 2022)
  • 2019 Conference chair, “Workshop on Optomechanics and Brillouin scattering - WOMBAT 2021”, Erlangen, Germany (planned for 16-18 June 2021)
  • 2019 Guest editor for APL Photonics for the Topical Issue “Optoacoustics - Advances in High-Frequency Optomechanics and Brillouin Scattering”
  • 2018 Co-Chair, “Nanophotonics 2018 – the next frontier”, Canberra, Australia
  • 2016 Co-Chair, “Quantum photonic connections conference”, Sydney, Australia
  • 2013 – 2015 Cusanuswerk career development program
  • 2011 Prix A’Doc 2011 of the Université Franche-Comté
  • 2009 – 2011 CNRS PhD Scholarship
  • 2009 Ohm-Preis 2008/2009 of the Physics department at the University of Erlangen-Nuremberg, Germany
  • 2004 – 2008 Scholarship Cusanuswerk

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