Geometry optimization for optical micromanipulation

The motion of a particle in an optical field is determined by the interplay between the geometry of the incident optical field, and the geometry and composition of the object. There are, therefore, two complementary roots to generating a particular force field. The first, involving sculpting of the optical field with, for example, a spatial light modulator, has been extensively developed. The second approach, which involves sculpting of the particles themselves, has been highlighted recently, but has received much less attention [J. Gluckstad, Nature Photonics, 5, 7-8 (2011)]. However, as modern fabrication methods advance, this avenue becomes increasingly attractive. In the following contribution we show how computational methods may be used to optimize particle geometries so as to reproduce desirable forms of behaviour. In particular, we exhibit a constant force optical spring for use as a passive force clamp in force sensing applications and a high efficiency optical wing.