LIGHT-DRIVEN MOLECULAR MOTOR

An all-optical control of light-angular-momentum transfer to nematic-l iquid-crystal molecules is carried out by two copropagating noncoheren t waves of orthogonal circular polarization. This allows the continuou s variation of the total angular momentum of the light while conservin g its circular symmetry. The molecular precession frequency is thus ef fectively and thoroughly controlled. The light-induced molecular reori entation threshold is shown to depend significantly on the azimuthal s ymmetry of the excitation light, while remaining the same for differen t values of its total angular momentum.