Presentation Information

[24a-P01-9]Optical Binding Dynamics of Gold Nanoparticles outside Two Co-propagating Laser Beams

〇(M2)Xin-Xiu Wang1, Mu-En Li1, Chih-Hao Huang1, Boris Louis2, Roger Bresoli-Obach3, Johan Hofkens2, Hiroshi Masuhara1, Yung-Fu Chen1 (1.Nat'l Yang Ming Chiao Tung Univ., Taiwan, 2.Ktholieke Univ. Leuven, Belgium, 3.Univ. Ramon Llull, Spain)


dual beam optical trapping,optical binding

Optical binding, observed for micro- and nano-particles, facilitates the light-driven assembly of complex multi-particle systems. Assembling phenomena can be explained in terms of optical potential. In regions with deeper potential wells, particles are more inclined to stay, consequently correlating the localization density of particles directly with the depth of the potential wells. We have demonstrated that, upon trapping gold (Au) nanoparticles (NPs) at the focal point, the scattered light produces multiple distinct arc-shaped potential wells with half-wavelength intervals of the trapping laser outside the focal spot1,2. The localization density of NPs decreases upon receding from the focus.
In this work, we introduce two co-propagating laser beams at separated positions to investigate the binding dynamics outside the focal spot. Au NPs can be trapped between and outside the focal points of two lasers, creating two optical binding systems. At initial stage of the trapping, a single Au NP is localized between the focal points of these two lasers (Fig. 1a), while it moves from time to time, giving the distribution of three potentials (Fig. 1b). The distance between the distribution peaks is similar to that of the conventional single beam binding system (Fig. 1c). These results imply that the potential energy constructed by two different incident beams are overlapped and might be interfered with each other. Many NPs are trapped with further irradiation, resulting in completely new optical trapping and swarming behaviors.