Trapping and patterning of biological objects using photovoltaic tweezers

Photovoltaic tweezers are a recently proposed technique for manipulation and patterning of micro- and nano-objects. It is based in the dielectrophoretic forces associated to the electric fields induced by illumination of certain ferroelectrics due to the bulk photovoltaic effect. The technique has been applied to the patterning of dielectric and metal micro- and nano-particles. In this work, we report the use of photovoltaic tweezers to pattern biological objects on LiNbO3:Fe. Specifically, spores and pollen grains and their nanometric fragments have been trapped and patterned. 1D and 2D arrangements have been achieved by deposition in air or from a hexane suspension. The quality of patterns obtained with nanometric fragments is even better than previous results using photovoltaic tweezers with inorganic micro- and nano-particles. In fact, 1D patterns with a period of 2 μm, almost half of the minimum reported period achieved with photovoltaic tweezers, have been obtained with pollen fragmentsThis work was supported by Spanish projects MAT2011-28379-C03 and MAT2014-57704-C0

Diffractive optical devices produced by light-assisted trapping of nanoparticles

© 2015 Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibitedOne and two-dimensional diffractive optical devices have been fabricated by light assisted trapping and patterning of nanoparticles. The method is based on the dielectrophoretic forces appearing in the vicinity of a photovoltaic crystal, such as Fe:LiNbO3, during or after illumination. By illumination with the appropriate light distribution, the nanoparticles are organized along patterns designed at will. One- and two-dimensional diffractive components have been achieved on X- and Z-cut Fe:LiNbO3 crystals, with their polar axes parallel and perpendicular to the crystal surface, respectively. Diffraction gratings with periods down to around a few micrometers have been produced using metal (Al, Ag) nanoparticles with radii in the range of 70-100 nm. Moreover, several 2D devices, such as Fresnel zone plates, have been also produced showing the potential of the method. The diffractive particle patterns remain stable when light is removed. A method to transfer the diffractive patterns to other non-photovoltaic substrates, such as silica glass, has been also reportedThis work was supported by Spanish projects MAT2011- 28379-C03 and MAT2014-57704-C0

Particle Patterning on Lithium Niobate waveguides via photovoltaic tweezers

Successful micro and nano-particle patterning on iron doped lithium niobate waveguides using photovoltaic fields is reported. This technique previously used in bulk crystals is here applied to waveguide configuration. Well defined particle patterns are obtained using two types of planar waveguides (by proton exchanged and swift heavy ion irradiation) and metallic and dielectric neutral particles. The use of waveguide configuration has allowed a reduction of the light exposure time until 3 s, two orders of magnitude smaller than typical values used in bulk

Analysis and optimization of propagation losses in LiNbO3 optical waveguides produced by swift heavy-ion irradiation

The propagation losses (PL) of lithium niobate optical planar waveguides fabricated by swift heavy-ion irradiation (SHI), an alternative to conventional ion implantation, have been investigated and optimized. For waveguide fabrication, congruently melting LiNbO3 substrates were irradiated with F ions at 20 MeV or 30 MeV and fluences in the range 1013–1014 cm−2. The influence of the temperature and time of post-irradiation annealing treatments has been systematically studied. Optimum propagation losses lower than 0.5 dB/cm have been obtained for both TE and TM modes, after a two-stage annealing treatment at 350 and 375∘C. Possible loss mechanisms are discussed

Characterization and inhibition of photorefractive optical damage of swift heavy ion irradiation waveguides in LiNbO 3

The photorefractive effect and the corresponding optical damage thresholds of novel LiNbO 3 waveguides fabricated by swift ion irradiation have been investigated. TE- and TM-mode operation have been characterized, and the influence of the beam propagation length analyzed. Optical damage levels similar to those of proton-exchanged waveguides have been found. In order to reduce optical damage, the influence of temperature has been investigated. An increase of more than a factor of 100 in the optical damage threshold has been obtained by moderate heating up to 90°C. The results are briefly discussed under the two-center model for the photorefractive effect in undoped LiNbO 3, and compared with data from other types of LiNbO 3 waveguides. © 2012 Optical Society of America.This work was supported by the Ministerio de Economia y Competitividad (MINECO) under grants MAT2008-06794- C03-01 and MAT2011-28379-C03-01.Peer Reviewe

Nonlinear optical waveguides fabricated in Mg-doped LiNbO3 by swift heavy ion irradiation: Anomalous photorefractive damage behavior

Using swift heavy fluorine ion irradiation, we have successfully fabricated optical waveguides in Mg-doped LiNbO3 substrates. A systematic characterization of these structures has been carried out including refractive index profiles, propagation losses, nonlinear coefficients, and, specially, photorefractive optical damage. Step-like refractive index profiles with Δn e ≈ 0.1 and Δn o ≈ 0.2, propagation losses lower than 0.5 dB/cm and high nonlinear optical coefficients similar to those of the substrate have been obtained. Unexpectedly, the photorefractive damage is only moderately reduced with regard to the one presented in congruent LiNbO3 waveguides. Specifically, light intensity damage thresholds I th are only a factor 2 higher at RT and a factor 4 at 90 °C with regard to undoped waveguides. At this latter temperature, a remarkably high I th = 30.000 W/cm2 is reached. A final discussion on the observed anomalous optical damage behavior induced by swift heavy ion irradiation is also included. © 2013 Springer-Verlag Berlin Heidelberg.This work was supported by projects MAT2008-06794-C03 and MAT2011-28379-C03-01. A FPI fellowship is acknowledged by Mariano Jubera.Peer Reviewe

Luminescence Properties Of Eu\u3csup\u3e3+\u3c/sup\u3e Or Dy\u3csup\u3e3+\u3c/sup\u3e/Au Co-Doped Sio2 Nanoparticles

Silica nanoparticles, prepared by the Stober method, have been doped with Eu3+, Dy3+, or processed to result in Au nanoparticles on the silica surface. The luminescence of the rare earth (RE)-doped SiO2 particles has been studied as a function of the nature of the RE, their concentration and also of the presence of Au nanoparticles at the surface of the SiO2 nanoparticles. We have shown that the Eu3+ emission is observable over the experimental conditions examined, whereas it was not possible to observe any emission for Dy3+ doped materials. No enhancement of the Eu3+ emission was observed following the adsorption of gold nanoparticles at the surface of the SiO2 nanoparticle, however an excitation at 250 nm leads to both the emission of the matrix and Eu3+ showing an energy transfer from the SiO2 matrix to Eu3+ ions. © 2007 Elsevier B.V. All rights reserved

Particle trapping and structuring on the surface of LiNbO3:Fe optical waveguides using photovoltaic fields

OCIS Codes (160.3730) Materials : Lithium niobate (190.5330) Nonlinear optics : Photorefractive optics (230.7390) Optical devices : Waveguides, planar (350.4855) Other areas of optics : Optical tweezers or optical manipulation.We report on the successful trapping and patterning of micro- and nanometric particles on the surface of LiNbO3 optical waveguides via photovoltaic tweezers. A waveguide configuration is used for the first time combined with this recently proposed technique. The electric field pattern is generated by light propagating in the waveguide, allowing us to separate the light channel with the region in which particles are deposited. Results on microand nanoparticle trapping, by two different deposition methods on two types of planar waveguides (by soft proton exchanged and by swift heavy ion irradiation), and using single-beam and two-beam interferometric configuration, are presented and discussed. © 2014 Optical Society of America.Peer Reviewe