We present a study of dynamical stabilisation of an overdamped, microscopic pendulum realised using optical tweezers. We first derive an analytical expression for the equilibrium dynamically stabilised pendulum position in a regime of high damping and high modulation frequency of the pendulum pivot. This model implies a threshold behavior for stabilisation to occur, and a continuous evolution of the angular position which, unlike the underdamped case, does not reach the fully inverted position. We then test the theoretical predictions using an optically trapped microparticle subject to fluid drag force, finding reasonable agreement with the threshold and equilibrium behavior at high modulation amplitude. Analytical theory and experiments are complemented by Brownian motion simulations.

Date Published: 10 March 2015
PDF: 7 pages
Proc. SPIE 9379, Complex Light and Optical Forces IX, 93790L (10 March 2015); doi: 10.1117/12.2078961

Published in SPIE Proceedings Vol. 9379:
Complex Light and Optical Forces IX
Enrique J. Galvez; Jesper Glückstad; David L. Andrews, Editor(s)