Light induced forces on dielectric nanospheres

Abstract

Waves that are reflected and refracted by material bodies also transfer momentum to these bodies. This means that the wave field induces a force on the bodies, and multiple reflections between bodies induce forces between them.

Light is an electromagnetic wave phenomenon, and the waves carry energy and momentum. Hence, any object that is scattering and refracting light is also acted upon by a light induced force. This force is a tiny force and is usually ignored, but if the objects are small enough the force induced by the light field would dominate all other forces. Due to this it is possible to manipulate small objects using light from a laser.

This thesis is based on an experiment on optical binding of two dielectric spheres, where the spheres were small enough to make the force induced by the light field the dominating force. In the experiment bistability and hysteresis in the equilibrium separations of the optically bound dielectric spheres were observed in one dimension. In this thesis the experiment will be modeled with a simplified setup, and the goal is to see if it is possible to find bistability in two dimensions also. Numerical approximations are used to calculate the wave field, and from this the force on the objects can be found.