Ultimate propulsion of wavelength-sized dielectric particles.

It is shown that a wavelength-sized dielectric particle can form a resonant state with the below-cutoff mode of a waveguide even for rather small values of the refractive index contrast between the particle and the background. The excitation of the resonant state creates the propelling force twice the momentum flow of the incident mode, and the particle is reliably trapped at the waveguide center. Since neither the particle nor the waveguide possesses individually any resonant properties, this operating regime can be applicable for the manipulation of particles of various materials, sizes, and shapes.