Optical binding of plasmonic nanoparticles offers a unique route to assemble mesoscale clusters and chains. However, stability is an issue that prevents assembling large-scale optical matter from nanoparticles. Here, we report a new method to study and improve the spatiotemporal stability of optical matter chains consisting of gold nanospheres by modulating the polarization direction of a linearly polarized optical line trap. The optical binding strengths of gold nanoparticles with parallel and perpendicular polarized light are different, resulting in versatile oscillation properties of the nanoparticles with polarization modulation. We show that the optical binding strength is spatially inhomogeneous along the nanoparticle chains depending on the total number and relative positions of particles, and it is temporally variable depending on the frequency of polarization modulation. In particular, the average oscillation amplitude of the particles can be tuned by increasing the frequency of polarization modulation. The spatiotemporal stability of the optically bound nanoparticles can be improved when the polarization modulation speed is fast and the optical binding is strong enough to suppress thermal motion. This study represents a new way to manipulate optical forces at mesoscale, and provides important information for assembling large-scale optical matter with nanoparticles.
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