Optical forces and directionality in one-dimensional PT-symmetric photonics

We discuss the optical forces exerted on parity-time (PT) symmetric heterostructures under normal incidence of a single and two counterpropagating plane waves. The underlying strategy is through generalized parametric space, stemming from consideration of the PT-symmetry condition and Lorentz reciprocity theorem. In such a generalized parametric space, we are able to not only exhaustively indicate various PT phases and extraordinary wave phenomena but also deduce the directionality and magnitudes of optical forces. We find that when the system is illuminated by a normally incident wave, it can exhibit the symmetric pushing effect in the exact symmetry phase, unidirectional null, and bidirectional null forces (BNF) at the exceptional point, and pulling-pushing flipped forces in the broken symmetry phase, with BNF found at the pushing-pulling turning point. In two counterpropagating plane wave interferences, the magnitudes as well as the directionality of the resultant optical force can be tuned by a relative phase of incident waves. More interestingly, we observe that a null force independent of the relative phase occurred in a specific region of the broken symmetry phase and exceptional point. In addition, we offer several PT-symmetric heterostructures to support our findings. Our results may benefit applications in PT optomechanics and force rectifiers.

Automated summary

The study examines the optical forces on PT symmetric heterostructures under different conditions, utilizing a generalized parametric space to analyze the directionality and magnitudes of forces. It is found that the forces exhibit different effects depending on the relative phases and conditions, with null forces observed in specific regions.