Research Group Hunger

Cavity Quantum Optics
Cavity with Diamond MembraneD. Hunger

Our group is exploring applications of optical microcavities in the fields of solid state quantum optics, optical sensing, microscopy, spectroscopy, and optomechanics.


Enhanced light-matter interactions allow one to realize efficient optical interfaces at the single quantum level, and enable novel schemes for spectroscopy and sensing. We employ and further develop fiber-based Fabry-Perot microcavities, which combine microscopic mode volumes with exceptionally high quality factors, and at the same time offer open access for a variety of samples. We use this highly flexible platform e.g. to realize a coherent spin-photon interface for NV centers in diamond, to read out and control individual rare earth ions as qubits, and to perform cavity-enhanced sensing and spectroscopy of nanosystems also in liquid environments.

Cavity with CNTs D. Hunger
Cavity with spins
Optically addressable spin qubits with rare earth ions
Cavity with NVs
Spin-photon interface with color centers in diamond
Sensing of individual nanosystems in liquids
CNT Raman map
Cavity-enhanced spectroscopy of carbon nanotubes
WS2 Flake
Polaritons in atomically thin semiconductors
SCM Picture
Scanning cavity microscopy of nanosystems


  • 02/20: new publication in collaboration with Ferdinand Schmidt-Kaler: Cryogenic platform for coupling color centers in diamond membranes to a fiberbased microcavity, arXiv:2002.08304
  • 01/20: new publication in collaboration with Hugues de Riedmatten: Dynamic control of Purcell enhanced emission of erbium ions in nanoparticles, arXiv:2001.08532
  • 10/19: From our group emerges the spin-off Qlibri, developing stable optical fiber micro cavities for quantum optics and cavity enhanced absorption microscopes.
  • 10/19: We could explain artefacts in scanning cavity microscopy, see the new paper.
  • 09/19: Our paper on Polaritons in WS2 is (finally!) published
  • 8/19: We have hosted the Quantum Futur Academy with more than 30 participants.
  • 7/19: We have hosted the SQUARE summer school with 60 participants.
  • 11/18: The Max Planck School of Photonics has launched, with a first call for students opened until 15.12.2018. We are participating and offer a PhD project within the school!
  • 10/18: The Quantum Flagship is now officially announced, and with it the project SQUARE where we are part of. Have a look at the press release and webpage SQUARE.
  • 10/18: Press release for the quantum repeater project online: link
  • 10/18: Quantum Flagship Kickoff announced (link): We will be part of it! Press release to come soon
  • 09/18: Paper accepted: B. Casabone et al., Cavity-enhanced spectroscopy of a few-ion ensemble in Eu:Y2O3, New Journal of Physics,
  • 09/18: Paper published: B. T. Walker et al., Driven-dissipative Bose-Einstein condensation of just a few photons, Nature Physics,
  • 08/18: BMBF-founded project "Quantum Link Extended" ( has started. We will contribute to realize a quantum repeater link based on color centers in diamond within Germany.
  • new publication: C. Gebhardt et al., Polariton hyperspectral imaging of two-dimensional semiconductor crystals,
  • new publication: B. Casabone et al., Cavity-enhanced spectroscopy of a few-ion ensemble in Eu:Y2O3,
  • new publication: P. R. Dolan et al., Robust, tunable, and high purity triggered single photon source at room temperature using a nitrogen-vacancy center defect in diamond in an open microcavity, Optics Express 26, 7056 (2018)
  • new publication: B. T. Walker et al., Driven-dissipative Bose-Einstein condensation of just a few photons,
  • new publication: M. Förg et al., Cavity-control of bright and dark interlayer excitons in van der Waals heterostructures:
  • Since mid of October 2017 our labs are (almost) ready and first experiments are running!
  • On 27. and 28.09.2017 we hosted the annual Rare Earth Ion Workshop with about 60 participants.