Dynamics of gravity-induced gradients in soap film thicknesses

G. Ropars, D. Chauvat, A. Le Floch, M. N. O'Sullivan-Hale and R. W. Boyd

Applied Physics Letters 88, 234104 (2006)

We demonstrate a direct measurement of thickness gradients in vertical soap films with a resonant differential interferometer, i.e., the Jamin-Fabry-Perot interferometer. Two regimes are investigated: thick colored films with gravity- and capillarity-induced gradients, and silvery-gray to common black films which are quasi-independent of gravity. In the colored zone, our differential method is an ideal tool with which to isolate the large thickness instabilities of the film reaching 17 nm/mm that characterize the end of its drainage. Using the so-called F2 law of such an interferometer, thermal-induced thickness variations as small as 1 nm are isolated in the gradient-free common black film

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