Standing-wave optical trap based on retro-reflection photonic nanojet

A new concept of an optical trap based on the retro-reflection standing-wave photonic nanojet (SWOT) is presented. An open resonance cavity is formed between two coaxial microparticles of different geometries (sphere, cylinder, ring, truncated cone) with one particle docked to a plain mirror and is exposed to a single optical source. Numerical simulations show the achievement of a substantial optical intensity enhancement in SWOT workspace, almost seven times higher than that of a conventional photonic nanojet trap, due to a triple-focused optical beam, which contributes to improved optical trapping. The proposed optical trap design allows for multi-position particle confinement in the trapping area. The advantages of the presented solution are the simple technical implementation and the possibility of integration with microfluidic technologies for optical manipulation of nanoobjects, e.g. Chip-on-flex optical sorting and ordering of nanoobjects, nanoparticle beaming.