Nicholas Guesken

All Publications

• Emission enhancement of erbium in a reverse nanofocusing waveguide. Nature communications Güsken, N. A., Fu, M., Zapf, M., Nielsen, M. P., Dichtl, P., Röder, R., Clark, A. S., Maier, S. A., Ronning, C., Oulton, R. F. 2023; 14 (1): 2719

  Abstract

  Since Purcell's seminal report 75 years ago, electromagnetic resonators have been used to control light-matter interactions to make brighter radiation sources and unleash unprecedented control over quantum states of light and matter. Indeed, optical resonators such as microcavities and plasmonic antennas offer excellent control but only over a limited spectral range. Strategies to mutually tune and match emission and resonator frequency are often required, which is intricate and precludes the possibility of enhancing multiple transitions simultaneously. In this letter, we report a strong radiative emission rate enhancement of Er3+-ions across the telecommunications C-band in a single plasmonic waveguide based on the Purcell effect. Our gap waveguide uses a reverse nanofocusing approach to efficiently enhance, extract and guide emission from the nanoscale to a photonic waveguide while keeping plasmonic losses at a minimum. Remarkably, the large and broadband Purcell enhancement allows us to resolve Stark-split electric dipole transitions, which are typically only observed under cryogenic conditions. Simultaneous radiative emission enhancement of multiple quantum states is of great interest for photonic quantum networks and on-chip data communications.

  View details for DOI 10.1038/s41467-023-38262-6

  View details for PubMedID 37169740

  View details for PubMedCentralID PMC10175264

• Emission enhancement of erbium in a reverse nanofocusing waveguide Nature Communications Güsken, N. A., et al 2023; 14 (2719)

  View details for DOI 10.1038/s41467-023-38262-6

• Near-unity Raman beta-factor of surface-enhanced Raman scattering in a waveguide. Nature nanotechnology Fu, M., Mota, M. P., Xiao, X., Jacassi, A., Gusken, N. A., Chen, Y., Xiao, H., Li, Y., Riaz, A., Maier, S. A., Oulton, R. F. 2022

  Abstract

  The Raman scattering of light by molecular vibrations is a powerful technique to fingerprint molecules through their internal bonds and symmetries. Since Raman scattering is weak1, methods to enhance, direct and harness it are highly desirable, and this has been achieved using optical cavities2, waveguides3-6 and surface-enhanced Raman scattering (SERS)7-9. Although SERS offers dramatic enhancements2,6,10,11 by localizing light within vanishingly small hot-spots in metallic nanostructures, these tiny interaction volumes are only sensitive to a few molecules, yielding weak signals12. Here we show that SERS from 4-aminothiophenol molecules bonded to a plasmonic gap waveguide is directed into a single mode with >99% efficiency. Although sacrificing a confinement dimension, we find a SERS enhancement of ~103 times across a broad spectral range enabled by the waveguide's larger sensing volume and non-resonant waveguide mode. Remarkably, this waveguide SERS is bright enough to image Raman transport across the waveguides, highlighting the role of nanofocusing13-15 and the Purcell effect16. By analogy to the beta-factor from laser physics10,17-20, the near-unity Raman beta-factor we observe exposes the SERS technique to alternative routes for controlling Raman scattering. The ability of waveguide SERS to direct Raman scattering is relevant to Raman sensors based on integrated photonics7-9 with applications in gas sensing and biosensing.

  View details for DOI 10.1038/s41565-022-01232-y

  View details for PubMedID 36302960