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Proceedings Paper

Optical Kapitza pendulum
Author(s): Philip H. Jones; Thomas J. Smart; Christopher J. Richards; David Cubero
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Paper Abstract

The Kapitza pendulum is the paradigm for the phenomenon of dynamical stabilization, whereby an otherwise unstable system achieves a stability that is induced by fast modulation of a control parameter. In the classic, macroscopic Kapitza pendulum, a rigid pendulum is stabilized in the upright, inverted pendulum using a particle confined in a ring-shaped optical trap, subject to a drag force via fluid flow and driven via oscillating the potential in a direction parallel to the fluid flow. In the regime of vanishing Reynold's number with high-frequency driving the inverted pendulum is no longer stable, but new equilibrium positions appear that depend on the amplitude of driving. As the driving frequency is decreased a yet different behavior emerges where stability of the pendulum depends also on the details of the pendulum hydrodynamics. We present a theory for the observed induced stability of the overdamped pendulum based on the separation of timescales in the pendulum motion as formulated by Kapitza, but with the addition of a viscous drag. Excellent agreement is found between the predicted behavior from the analytical theory and the experimental results across the range of pendulum driving frequencies. We complement these results with Brownian motion simulations, and we characterize the stabilized pendulum by both time- and frequency-domain analyses of the pendulum Brownian motion.

Paper Details

Date Published: 16 September 2016
PDF: 8 pages
Proc. SPIE 9922, Optical Trapping and Optical Micromanipulation XIII, 992202 (16 September 2016); doi: 10.1117/12.2239604
Show Author Affiliations
Philip H. Jones, Univ. College London (United Kingdom)
Thomas J. Smart, Univ. College London (United Kingdom)
Christopher J. Richards, Univ. College London (United Kingdom)
David Cubero, Univ. de Sevilla (Spain)

Published in SPIE Proceedings Vol. 9922:
Optical Trapping and Optical Micromanipulation XIII
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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