Reconfigurable Size‐Sorting of Micronanoparticles in Chalcogenide Waveguide Array

Abstract

Optical tweezers are considered as a revolution, allowing for manipulating particles ranging in scale from a few hundred nanometers (nm) to several micrometers (μm). Near-field optical force allows effective trapping of a broad range of entities, from atom to living cells. Yet, there are formidable challengings for existing on-chip photonic trapping techniques to simultaneously handle at will multiple entities with cross-scales (i.e., from nm to μm). Herein, optical transportation and trapping of polystyrene particles with the different diameters are demonstrated in optofluidic nanophotonic sawtooth waveguide array (ONSWA) made of chalcogenide alloys Sb2Se3. The chalcogenide ONSWA produces sawtooth-like light fields that can be actively modulated via the phase transition of Sb2Se3. Particularly, the chalcogenide ONSWA can stably trap the polystyrene particles with the diameters of 500 nm and 1 μm for both the amorphous and crystalline states, respectively. It is experimentally demonstrated that the phase transition of Sb2Se3 from amorphous to crystalline and vice versa can be achieved in nanoseconds. Using the technique of nanosecond laser-induced phase transition of Sb2Se3, a dynamically reconfigurable size-sorting of objects on the identical ONSWA is proposed.