Pulling electromagnetic force induced by virtual excitation

Here, we revisit the issue of optical forces by stepping out to the complex frequency plane and considering its dynamics upon complex excitations. We show that tailoring the time evolution of the light excitation field allows pulling force for a Fabri-Perot resonator. This effect is linked to virtual gain, which can be achieved by exponentially decaying excitation signal weaker than the outgoing signal that carries away greater energy and momentum flux density.