Using a boundary element method to calculate electromagnetic fields and the Maxwell stress tensor method to compute electromagnetic forces, we investigate electromagnetic wave induced forces acting on a pair of identical metal plates that form an electromagnetic resonance cavity. Different frequency regimes are considered, from infrared frequencies with micron-scale structures down to the microwave regime, which involves millimeter-scale structures. We found that at both length scales, electromagnetic-wave-induced forces can be significantly stronger than the usual photon pressure exerted by a laser beam if the cavity is excited at resonance, although the mechanisms that underlie the strong force are different at different length scales. In the infrared frequency regime, the strong force is induced by field penetration into the metal, whereas in the microwave regime, the electromagnetic force is induced by the leakage of electric field at the edges. At both frequency scales, we compare the results we obtained for Au metal plates with fictitious perfect electric conductor plates, so as to understand the effect of field penetration. We also showed that a transmission line model can give simple expressions that can capture the essence of the physics. The effects of surface corrugation and surface roughness are also investigated, and we find that corrugation/roughness generally induces attraction between the plates.

• Received 4 March 2011

DOI:https://doi.org/10.1103/PhysRevB.84.075114