Scanning cavity microscopy

Improving the sensitivity of optical microscopy could give access to the optical properties of a large class of interesting nanoscale systems on a single particle level. To boost sensitivity, we are developing a novel scanning microscopy technique that harnesses multiple interactions of probe light with an object. This is realized by placing the sample inside a high-finesse optical microcavity, which provides a signal enhancement on the order of the cavity Finesse (10⁴ – 10⁵). Raster-scanning the sample through the cavity mode enables us to obtain spatial maps of sample absorption, dispersion, and birefringence of individual nanoparticles.

The method should enable e.g. the spectroscopic characterization of individual nanoparticles, dispersive sensing with high spatial resolution, and the detection of non-fluorescent single molecules. [Mader et al., Nature Commun (2015), Hümmer et al., Nature Commun. (2016), Mader et al., ACS Photonics (2022)].