Christophe Galland

Placing an emitter or a scatterer in a cavity modifies its local photonic environment. It boosts light-matter interaction, which can be used to improve the performance of single-photon sources [1] or to perform nonlinear spectroscopy on individual molecules [2,3]. 

I will first illustrate how to achieve ultra-broadband photonic engineering using self-assembled plasmonic nanocavities. We realize single-molecule Purcell factors of 10^5 and a giant enhancement of three-wave mixing by 10^12, enabling coherent vibrational spectroscopy at the few-molecule level [4-8].

The second part of the presentation will be devoted to diamond nanophotonics. I will present our platform for realizing suspended single-crystal diamond nanostructures and how it is used in two different contexts: for the study of nanoscale non-diffusive phonon heat transport probed by NV thermometers [9], and for the implementation of cavity-enhanced NV spin readout through the singlet transition absorption measurement at 1’042 nm [10]. 

References:

[1] L. Husel, A., et al. “Cavity-enhanced photon indistinguishability at room temperature and telecom wavelengths.” [Nature Communications 15, 3989 (2024)](https://doi.org/10.1038/s41467-024-48119-1)

[2] Schörner, C and Lippitz, M. “Single molecule nonlinearity in a plasmonic waveguide.” [Nano Letters 20, 2152-2156 (2020)](https://doi.org/10.1021/acs.nanolett.0c00196)

[3] Maser, A., Gmeiner, B., Utikal, T., Götzinger, S., & Sandoghdar, V. “Few-photon coherent nonlinear optics with a single molecule.” [Nature Photonics, 10, 450-453 (2016)](https://doi.org/10.1038/nphoton.2016.63)

[4] Verlekar, S. et al. “Giant Purcell broadening and Lamb shift for DNA-assembled near-infrared

quantum emitters”, [ACS Nano 19, 3172–3184 (2025)](https://doi.org/10.1021/acsnano.4c09829)

[5] Chen, W. et al. “Continuous-wave frequency upconversion with a molecular optomechanical nanocavity.” [Science 374, 1264-1267 (2021)](https://doi.org/10.1126/science.abk3106)

[6] Hu, H. et al. “Plasmonic Nanoparticle-in-nanoslit Antenna as Independently Tunable Dual-Resonant Systems for Efficient Frequency Upconversion” (2025) [preprint: arXiv:2505.10668](https://doi.org/10.48550/arXiv.2505.10668)

[7] Moradi Kalarde, F. et al, “Photon antibunching in single-molecule vibrational sum-frequency generation” [Nanophotonics 14, 59-73  (2025)](https://doi.org/10.1515/nanoph-2024-0469)

[8] Xie, Z et al. “Continuous-wave, high-resolution, ultra-broadband mid-infrared nonlinear spectroscopy with tunable plasmonic nanocavities” arXiv:2508.12097

[9] Goblot, V. et al. “Imaging heat transport in suspended diamond nanostructures with integrated spin defect thermometers ”arXiv:2411.04065

[10] Zhu, Y. et al. “Fiber-Coupled Diamond Microcavities for Infrared Absorption Readout of NV Centers”  CLEO 2025, paper SS114_5