title: Interferometric tracking of optically trapped probes behind structured surfaces: A phase correction method.
abstract: We investigate the influence of an additional scatterer on the tracking signal of an optically trapped particle. The three-dimensional particle position is recorded interferometrically with nanometer precision by using a quadrant photodiode in the back focal plane of a detection lens. A phase disturbance underneath the sample leads to incorrect position signals. The resulting interaction potential and forces are therefore erroneous as well. We present a procedure to correct for the disturbance by measuring its interferometric signal. We prove the applicability of our phase correction approach by generating a defined displacement of the trapped probe.
authors.affiliation: European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany. p.seitz@gmx.net
authors.forename: Peter C
authors.initials: PC
authors.lastname: Seitz
authors.forename: Ernst H K
authors.initials: EH
authors.lastname: Stelzer
authors.forename: Alexander
authors.initials: A
authors.lastname: Rohrbach