We propose a technique for the characterization of a 1D-periodic optical potential by studying the dynamics of non-brownian microscopic particles immerse in water (negligible thermal noise). It has been demonstrated that in the Mie regime, a periodic light pattern applied to a particle acts as an effective potential that depends on the size of the particle respect to the period of the optical landscape [I. Ricardez-Vargas, et.al. Appl. Phys. Lett. 88, 121116 (2006)]. We verify this fact by studying the dynamics of a particle moving within the pattern due to the effect of a known constant external force. The periodic light pattern is generated with interference techniques whereas the external force is applied by means of a controlled inclination of the sample cell. We fit the experimental results for the ensemble average of particle position against time with a theoretical model of the physical situation. In this way we obtain a curve for the optical force as a function of particle's position for different periods.

Date Published: 29 August 2008
PDF: 9 pages
Proc. SPIE 7038, Optical Trapping and Optical Micromanipulation V, 703825 (29 August 2008);

Published in SPIE Proceedings Vol. 7038:
Optical Trapping and Optical Micromanipulation V
Kishan Dholakia; Gabriel C. Spalding, Editor(s)