Optical trapping of dielectric ellipsoids

Having three distinct radii, ellipsoidal particles can be rigidly bound in Gaussian traps. The elongated intensity profile of the beam exerts forces that both confine, and orient the particle whilst the polarization of the beam provides a further orientational constraint. Consequently, the longest axis of the ellipsoid tends to align itself with the beam axis and the next longest with the polarization direction. In this article we examine the optical force fields experienced by ellipsoidal particles in Gaussian beams. The relationship between the general properties of these traps, especially their stability and stiffness, with particle shape is investigated.