Optical Pulling and Pushing Forces in Bilayer PT-Symmetric Structures

We investigate the optical force exerted on a parity-time-symmetric bilayer made of balanced gain and loss. We show that an asymmetric optical pulling or pushing force can be exerted on this system depending on the direction of impinging light. The optical pulling or pushing force has a direct physical link to the optical characteristics embedded in the non-Hermitian bilayer. Furthermore, we suggest taking advantage of the optically generated asymmetric force to launch vibrations of an arbitrary shape, which is useful for the contactless probing of mechanical deformations.