Control and sorting of inhomogeneous dielectric core–shell nanoparticles using two counter-propagating plane waves

Many typical nanoscale structures consist of dielectric nanoparticles with an inevitable oxide-generated coating around them. Depending on the fabrication techniques and the intended purposes, these coatings may not be homogeneous, and their distortion can cause advantages or disadvantages in the applications of such systems. Based on finite element simulations, inhomogeneous core–shell nanoparticle systems are numerically studied when illuminated with two counter-propagating plane waves in the optical range. It is found that the electromagnetic field distortions caused by the inhomogeneous system under Mie resonance conditions allow the system to exhibit controllable one-directional impulsion and rotation, which mainly depends on the offset between the core and shell. The overall geometry and composition of the system also dictate the type of resonance being excited. Overall, this “photonic thruster” effect consisting of an accelerating and spinning projectile would provide stability to particle movement and additionally establish a method to distinguish inhomogeneous from homogeneous particles. The method can be scaled to a wide range of nanoscale dielectric particles. Thus, the results are useful for detecting defects in nanosystems with a simple concept and may open avenues for improving nanoparticle synthesis methods.