We have developed a multifocal optical fluorescence correlation spectroscopy system for parallel flow analyses. Multifocal excitation was made possible through a 4 × 1 diffractive optical fan-out element, which produces uniform intensity in all four foci. Autocorrelation flow analyses inside a 20 μm × 20 μm square microchannel, with the 4 × 1 fan-out foci perpendicular to the flow direction, made it possible to monitor different flows in all four foci simultaneously. We were able to perform cross-correlation flow analyses by turning the microstructure, thereby having all four foci parallel to the direction of flow. Transport effects of the diffusion as a function of flow and distance could then also be studied.
© 2002 Optical Society of America
(050.1950) Diffraction and gratings : Diffraction gratings
(220.4000) Optical design and fabrication : Microstructure fabrication
(280.2490) Remote sensing and sensors : Flow diagnostics
(300.2530) Spectroscopy : Fluorescence, laser-induced
Hans Blom, Mathias Johansson, Michael Gösch, Toni Sigmundsson, Johan Holm, Sverker Hård, and Rudolf Rigler, "Parallel Flow Measurements in Microstructures by Use of a Multifocal 4 x 1 Diffractive Optical Fan-Out Element," Appl. Opt. 41, 6614-6620 (2002)