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MO: Fachverband Molekülphysik

MO 18: Experimentelle Techniken

MO 18.2: Talk

Thursday, March 5, 2009, 11:00–11:15, VMP 6 HS-F

Improving background rejection in femtosecond fluorescence Kerr-gating — •Gerald Ryseck, Björn Heinz, Thomas Schmierer, and Peter Gilch — Ludwig-Maximilians-Universität München, Lehrstuhl für BioMolekulare Optik, 80538 München, Deutschland

Optical gates for ultrafast fluorescence measurements commonly rely on the up-conversion or the Kerr effect. Since Kerr-gating requires no phase matching, broadband detection schemes can be easily realized [1]. This advantage over up-conversion comes at the expense of a poorer performance for long-lived fluorophores. The background rejection as the limiting factor in Kerr-gating setups crucially depends on the extinction ratio of the gate polarizers. Effects that influence this parameter are large angles of incident on the polarizers and depolarization by reflective components.

We investigated the optical effects limiting the accessible time range and introduced methods to overcome this obstruction. With the ad- vanced setup it is possible to trace emissions with lifetimes up to several 100 ps. As a demonstration for the improved performance emission data of a photo-reactive N-oxide are presented. It features decay times ranging from 100 fs to 200 ps.

[1] B. Schmidt et al., Appl. Phys. B 76 (2003) 809-814