Selective transport of chiral particles by optical pulling forces

Abstract

We propose a simple approach for chirality sorting based on the optical pulling forces. The scenario is to employ three simple plane waves with the same circular polarization. The three wave vectors have the same longitudinal positive z component while their corresponding transverse projections in the x-o-y plane form a regular triangle. In such an optical lattice, particles with certain chirality will be drawn by the transverse optical force to the periodic intensity maxima, where they are stably trapped and exerted by an optical pulling force along the negative z direction. On the contrary, particles with the opposite chirality are de-trapped transversely away from the intensity maxima and then dispersed in regions where they subject to a positive (pushing) force along the z direction. The phenomena therefore give rise to an alternative all-optical method for selective transport of chiral particles with a wide range of chirality parameters.

Optical manipulation: from fluid to solid domains

“…For the second approach, chiral particles have been widely exploited to couple the light angular momentum to mechanical linear momentum. Sometimes, with a delicate arrangement of the particle chirality as well as light polarization, this angular-to-linear momentum cross-coupling can give rise to the optical pulling force [184–186] . Particles with negative polarizability can be propelled against the light propagation direction by either the optical gradient force or scattering force [187,188] .…”

Enantioselective optical forces in gain-functionalized single core-shell chiral nanoparticles

“…The separation of chiral enantiomers is an important scientific and technological task with many multidisciplinary applications [6,7]. In the last decades, considerable effort and progress have been made on the development of highly efficient optical enantioselective methods, such as enantioselective optical trapping [8][9][10][11], oppositely directed lateral forces [12][13][14], enantioselective pulling forces [15,16], and azimuthal/longitudinal optical torques [17,18]. Despite the rich literature in optical enantioselective schemes, they typically involve the trapping of a lossless particle using a structured optical beam or tightly focused beam.…”