Micro- and nano-particle trapping using fibered optical nano-tweezers Jean-Baptiste Decombe a , G´ eraldine Dantelle a,b , Thierry Gacoin b , Francisco J. Valdivia-Valero c , G´ erard Colas des Francs c , Serge Huant a , and Jochen Fick a * a Univ. Grenoble Alpes, Institut N´ eel, 38042 Grenoble, France CNRS, Institut N´ eel, 38042 Grenoble, France b Physique de la Mati` ere Condens´ ee, CNRS UMR 7643 Ecole Polytechnique, 91128 Palaiseau, France c Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS UMR 6303 Universit´ e de Bourgogne, 21078 Dijon, France ABSTRACT We present the stable trapping of luminescent 300-nm cerium-doped YAG particles in aqueous suspension using a dual fiber tip optical tweezers. The particles were elaborated using a specific glycothermal synthesis route together with an original protected annealing step. We obtained harmonic trap potentials in the direction transverse to the optical fiber axes. In the longitudinal direction, the potential shows some sub-structure revealed by two peaks in the distribution statistics with a distance of about half the wavelength of the trapping laser. We calculated intensity normalized trapping stiffness of 36 pN·µm −1 W −1 . These results are compared to previous work of microparticle trapping and discussed thanks to numerical simulations based on finite element method. Keywords: Optical tweezers, optical fibers, optical trapping, luminescent nano-particles. 1. INTRODUCTION Optical tweezers are well-established since the pioneering work of A. Ashkin. 1 This non-contact technique is of large interest in many scientific domains such as biochemistry, physics and medicine. In this context, the use of optical fibers attracts increasing attention as highly flexible tool for particle trapping. Fiber-based optical tweezers provide easy access to the trapped particle, which is useful for the implementation of further manipulation or characterization elements. Examples of tweezers with two facing optical fibers include micro-fluidic actuators using two cleaved fibers, 2 tweezers based on fiber tips grown by photo-polymerization 3 or using tapered lensed fiber tips. 4 Single fiber tip tweezers were realized with micro-lensed cleaved fibers, 5 multicore lensed fibers, 6 single- or multi-mode chemically etched fiber tips, 7, 8 gradient index chemically etched fiber tips creating 3D bottle beams 9 or using a bowtie plasmonic aperture at the extremity of a tapered metal-coated optical fiber. 10 Optical trapping of fluorescent nanometer-sized dielectric particles using two optical fiber tips are presented. This kind of chemically etched fiber tips is currently used for optical scanning microscopy such as NSOM 11 or iSOM. 12 YAG:Ce 3+ particles are selected for their high luminescent properties in the visible and their good colloidal stability in water. 13 They are synthesized using a specific glycothermal synthesis route together with an original protected annealing step. 14, 15 The trapping characteristics for micro and nano-particles are compared. Finally, the forces acting on the nano-particles are discussed within the dipolar approximation (gradient and scattering force contributions) or exact calculations using the Maxwell Stress Tensor (MST) formalism. ∗ jochen.fick@neel.cnrs.fr; http://perso.neel.cnrs.fr/jochen.fick/ Optical Trapping and Optical Micromanipulation XI, edited by Kishan Dholakia, Gabriel C. Spalding, Proc. of SPIE Vol. 9164, 916430 · © 2014 SPIE CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2061623 Proc. of SPIE Vol. 9164 916430-1