Curvilinear optical forces

Accelerating a light beam makes a particle move along a curvilinear trajectory. We show that the curvature of the trajectory causes a special kind of nonconservative force, which is called a curvilinear force. We obtain the expression for this force acting on a spherical particle in the Rayleigh approximation and determine its value for several types of accelerating fields including Bessel, Airy, and arbitrary-trajectory beams. We anticipate applications of the curvilinear forces in optical micromanipulation with accelerating beams.