Scattering Forces from the Curl of the Spin Angular Momentum of a Light Field

Silvia Albaladejo (1) , Manuel I. Marques (2) , Marine Laroche (3) , Juan-José Saenz (1)

1 Departamento de Fisica de la Materia Condensada and Instituto "Nicolas Cabrera"
2 Departamento de Fisica de Materiales C-IV
3 Laboratoire Charles Fabry de l'Institut d'Optique / Naphel

Light forces on small (Rayleigh) particles are usually described as the sum of two terms: the dipolar or gradient force and the scattering or radiation pressure force. The scattering force is traditionally considered proportional to the Poynting vector, which gives the direction and magnitude of the momentum flow. However, as we will show, there is an additional nonconservative contribution to the scattering force arising in a light field with nonuniform helicity. This force is shown to be proportional to the curl of the spin angular momentum of the light field. The relevance of the spin force is illustrated in the simple case of a 2D field geometry arising in the intersection region of two standing waves.

Domaines: Optique / photonique; Optique [physics.optics]

Silvia Albaladejo, Manuel I. Marques, Marine Laroche, Juan-José Saenz. Scattering Forces from the Curl of the Spin Angular Momentum of a Light Field. Physical Review Letters, 2009, 102 (11), pp.113602. ⟨10.1103/PhysRevLett.102.113602⟩. ⟨hal-00669771⟩