We are interested in the manipulation and characterization of optical fields on the nanometerscale. To this end we have investigated resonant optical antennas -metallic nano structures inspired by radiowave antenna technology. Despite the finite conductivity of metals at optical frequencies we have observed pronounced antenna resonances that are enhanced by plasmonic effects. We are currently progressing in the following fields:

(i) Implementation of antenna-based scanning near-field optical microscopy and spectroscopy with sub-10nm spatial resolution and single-molecule sensitivity.

(ii) Investigation of improved antenna designs to study the fundamental limits of optical field enhancement achievable in resonant optical antennas.

(iii) Coupling of single emitters to optical antennas to create optical "superemitters"

Detection, tracking and spectroscopy of single fluorescent molecules has developed into a powerful technique to study heterogeneous systems such as living organisms. Single-particle studies yield distributions of parameters and thus are ideally suited to study transient events, like the activation of a channel protein or specific interactions of molecules in the cellular context. We are interested in studying the kinetics of the cellular signaling cascade triggered by G-protein coupled receptors as well as in transport and interactions of virus particles in living cells by stuying single-molecule dynamics and interactions.

Detecting a single molecule represents the ultimate limit in optical sensors. We are interested in the development of single-molecule sensing schemes based on optical waveguides that are compatible with lab-on-the-chip technologies.