Giant resonant enhancement of optical binding of dielectric particles

Optical coupling of two identical dielectric particles gives rise to bonding and antibonding resonances. The latter is featured by significant narrowing of the resonant width and strong enhancement of the $Q$ factor for the high-index micron-size particles in subwavelength range. We consider particles shaped as spheres and disks under coaxial illumination of dual incoherent counterpropagating Bessel beams. In the case of spheres we derive analytical expressions for the optical binding (OB) force which decays and displays two periods of oscillations. For close distances the OB force enormously increases in the resonant regime. The case of two coaxial disks is featured by extremal enhancement of the $Q$ factor owing to the twofold variation over the distance between disks and the aspect ratio of each disk compared to the case of two spheres. In that case we demonstrate enhancement of the OB force up to several tens of nanonewtons. We show that the magnitude and sign of the OB force strongly depend on the longitudinal wave vector of the Bessel beams.