Vincent Ginis

Subfemtonewton Force Spectroscopy at the Thermal Limit in Liquids

L Liu, S Kheifets, V Ginis, F Capasso
We demonstrate thermally limited force spectroscopy using a probe formed by a dielectric microsphere optically trapped in water near a dielectric surface. We achieve force resolution below 1 fN in 100 s, corresponding to a 2 Å rms displacement of the probe. Our measurement combines a calibrated evanescent wave particle tracking technique and a lock-in detection method. We demonstrate the accuracy of our method by measurement of the height-dependent force exerted on the probe by an evanescent wave, the results of which are in agreement with Mie theory calculations.

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L Liu, S Kheifets, V Ginis, F Capasso