Bessel beam approach for photovoltaic trapping of micro- and nanoparticles on Fe-doped lithium niobate crystal

Abstract

The non-diffracting Bessel beam approach was used for the first time for the elaboration of photovoltaic tweezers. We report the trapping of dielectric microparticles of chalk (CaCO3), as well as silver nanoparticles in glycerin suspension via dielectrophoretic forces on the surface of Fe doped LiNbO3 (LN:Fe) crystal with recorded volume holographic grating by the non-diffracting Bessel beam technique. The photorefractive Y-cut LN:Fe crystal was illuminated by 20–40 mW power Bessel beam at 532 nm wavelength which generates refractive Bessel lattice with ~40 μm periodicity via induction of photovoltaic space-charge fields. The Bessel beam approach provides the induction of high contrast 2D quasi-periodic distribution of space-charge electric field in the crystal volume and proximity of the crystal surface and high quality 2D patterning of the particles. Experiments showed that CaCO3 microparticles are trapped by attractive forces on the crystal surface in the areas of refractive index maxima of the Bessel lattice, while the trapping of Ag nanoparticles dispersed in glycerin takes places at the borderlines of lattice rings due to the repulsive forces. A physical model was developed to explain the experimental results. The photovoltaic approach of trapping and manipulation of micro- and nanoparticles is promising for applications in photonics, integrated optics and biotechnology.