Optical manipulation of nanoscale materials by linear and nonlinear resonant optical responses

Realization of technologies for the mechanical manipulation (trapping, transportation, positioning, and aligning) of individual nanoscale particles has been an aspiration of researchers in various fields. Such technologies would enable us to manipulate nanomaterials, such as molecules, quantum dots, and nanocarbons, in a direct and selective way according to their individual quantum properties. Laser cooling and laser tweezers have been established as methods of remote manipulation of small objects for the atomic and micro-sized regimes, respectively. Despite the great successes of these technologies, the optical manipulation of nanoscale materials is still challenging because the thermal disturbance from the environment must be overcome by the very weak force on nanoscale objects. Technologies for selectively manipulating individual nanomaterial would enable the creation of structural order through optical sorting and isolation of targets according to their quantum individualities, and enable manipulation of chemical processes by selective control of molecular diffusion and condensation. In this article, we review recent studies on optical force on nanomaterials, mainly focusing on that arising from the linear and nonlinear optical responses due to electronic resonance of nanoparticles, and discuss the possibility of establishing nanoscale optical manipulation that could potentially contribute to the science and technology supporting our daily lives.