Whirl-enhanced continuous wave laser trapping of particles

Stanislaw Bartkiewicz and Andrzej Miniewicz

Tightly focused laser beams can trap micro- and nanoparticles suspended in liquids in their focal spots enabling different functionalities including 3D manipulations and assembling. Here, we report on a remarkable strength liquid-liquid phase separation and crystallization experiments in para-nitroaniline dissolved in 1,4-dioxane. For optical trapping of the para-nitroaniline we used partially absorbed by solute low-power, weakly focused light beam from continuous-wave laser. The experiments were performed for solution deposited on glass with upper free-surface and solution contained between two glass plates. The usual gradient field force and scattering force solely are insufficient to properly describe the observed particle gathering effects extending far beyond the optical trap potential. The concept of whirl-enhanced and temperature assisted optical trapping is postulated. The relative simplicity of the used geometry for trapping will broaden the understanding of the light-matter interaction and promises widespread application of the observed effect in optically controlled crystallization.

DOI