Active, reactive and instantaneous optical forces on small particles in the time domain: ultrafast attosecond subcycle pulses

Abstract

Recently discovered reactive optical forces have a null time-average of their instantaneous values on monochromatic illumination, so that their detection suggests the use of ultrafast optics, especially in the femto- and attosecond domains. Using illumination with subcycle attosecond evanescent pulses, we report a theoretical study of the time variations of instantaneous forces and the behaviour of reactive forces versus those active on small resonant particles that we consider dipolar. We demonstrate how the structure of these pulses permits us to obtain three remarkable novel effects on electric dipoles, namely a lateral force, a pulling force against the canonical and Poynting momenta of the wavefield and a levitating effect on the particle under repetition of the pulse. We hope that this study will inaugurate novel research in the area of optical manipulation. Future developments and experiments based on this theory should increase insight into and operation of the ultrafast dynamics of nanostructures.