Electromagnetic forces in negatively refracting photonic crystals

It is well known that electromagnetic (EM) waves exert forces on objects. Nonconservative part of these forces is determined by the gradient of phase (wavevector) of EM field. Using special structures, it is possible to manipulate the direction of these forces. In this paper, we numerically investigate the forces generated by left-handed negatively refracting photonic crystals which can create EM waves with Poynting vector and wave vectors having opposite directions. We show here that negative gradient of phase still creates a positively directed electromagnetic force.