Optohydrodynamic theory of particles in a dual-beam optical trap

We present an optohydrodynamic theory to treat optical interactions of particles. When applied to dielectric microsphere particles in a dual-beam optical trap, the theory explains the inhomogeneous self-organization and the spontaneous emergence of self-sustained oscillations. In the presence of small-scale symmetry breaking, self-sustained oscillations are shown to occur spontaneously from an exchange between the optical scattering and the gradient optical forces, in the absence of inertia that is central to the dynamics of ion traps. Experiments are provided that agree quantitatively with the theory. The optohydrodynamic theory is generally applicable to optical-particle configurations, and it is an important step toward explaining other physical phenomena that arise from optical interactions.