title: Adaptive optics for fluorescence correlation spectroscopy.
abstract: Fluorescence Correlation Spectroscopy (FCS) yields measurement parameters (number of molecules, diffusion time) that characterize the concentration and kinetics of fluorescent molecules within a supposedly known observation volume. Absolute derivation of concentrations and diffusion constants therefore requires preliminary calibrations of the confocal Point Spread Function with phantom solutions under perfectly controlled environmental conditions. In this paper, we quantify the influence of optical aberrations on single photon FCS and demonstrate a simple Adaptive Optics system for aberration correction. Optical aberrations are gradually introduced by focussing the excitation laser beam at increasing depths in fluorescent solutions with various refractive indices, which leads to drastic depth-dependent bias in the estimated FCS parameters. Aberration correction with a Deformable Mirror stabilizes these parameters within a range of several tens of μm into the solution. We also demonstrate, both theoretically and experimentally, that the molecular brightness scales as the Strehl ratio squared.
authors.affiliation: Université Grenoble 1/CNRS, LIPhy UMR 5588, Grenoble, France.
authors.forename: Charles-Edouard
authors.initials: CE
authors.lastname: Leroux
authors.forename: Irène
authors.initials: I
authors.lastname: Wang
authors.forename: Jacques
authors.initials: J
authors.lastname: Derouard
authors.forename: Antoine
authors.initials: A
authors.lastname: Delon
mesh_terms: D016477:Artifacts; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005246:Feedback; D007909:Lenses; D055096:Optical Devices; D013050:Spectrometry, Fluorescence / Q000295:instrumentation*