Bonn 2025 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 49: Poster – Photonics, Lasers, and Applications

Q 49.14: Poster

Mittwoch, 12. März 2025, 17:00–19:00, Tent

Label-free single nanoparticle sensing with a high-finesse microcavity — •Shalom Palkhivala, Larissa Kohler, and David Hunger — Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany

Since many biochemical processes occur in aqueous environments, the sensing and characterisation of single, unlabelled particles in water is of interest in fields of science such as biophysics and chemistry.

We demonstrate an open-access optofluidic platform for the label-free sensing of nanoparticles in aqueous suspension, using a fibre-based Fabry-Perot microcavity with high finesse (5 × 10⁴ in water) [1]. By monitoring interactions between diffusing nanosystems and the optical cavity field, the dynamics of the nanosystems can be investigated. The analysis of diffusion dynamics allows us to measure the hydrodynamic size of single particles with diameters of down to a few nanometers.

Furthermore, the rotational dynamics of anisotropic particles are investigated by interrogating orthogonal polarization modes of the cavity. Thus, the rotation of single nanorods could be tracked with high temporal resolution (∼ 10 ns), which is orders of magnitude faster than most other current techniques.

As an application of our sensor to the field of biosensing, we demonstrate the measurement of proteins, and detect single DNA "origami" structures.

[1] Kohler, L. et al. Nat Commun 12, 6385 (2021).

Keywords: optical microcavity; single particle sensing; label-free detection