Enhancing Nanoparticle Electrodynamics with Gold Nanoplate Mirrors

Abstract

Mirrors and optical cavities can modify and enhance matter-radiation interactions. Here we report that chemically synthesized Au nanoplates can serve as micrometer-size mirrors that enhance electrodynamic interactions. Because of their plasmonic properties, the Au nanoplates enhance the brightness of scattered light from Ag nanoparticles near the nanoplate surface in dark-field microscopy. More importantly, enhanced optical trapping and optical binding of Ag nanoparticles are demonstrated in interferometric optical traps created from a single laser beam and its reflection from individual Au nanoplates. The enhancement of the interparticle force constant is ≈20-fold more than expected from the increased intensity due to standing wave interference. We show that the additional stability for optical binding arises from the restricted axial thermal motion of the nanoparticles that couples to and reduces the fluctuations in the lateral plane. This new mechanism greatly advances the photonic synthesis of ultrastable nanoparticle arrays and investigation of their properties.

Driven optical matter: Dynamics of electrodynamically coupled nanoparticles in an optical ring vortex

“…We also perform comparative experiments with these nanoplarticles trapped near an electrostatically slightly charged (repulsive) glass surface. We show that multiple nanoparticles in the optical vortex are electrodynamically coupled via optical binding interactions, [14,38,46,47] resulting in the formation of optical matter [48], which is in distinct contrast with the hydrodynamically coupled microparticles in nearly all previous reports. The use of metal nanoparticles and the concomitant strong optical-binding interactions are key aspects of our study.…”

“…As previously shown [46,47,57], Ag nanoparticles interact electrodynamically via optical binding; a periodic modulation of the electric field in the vicinity of the nanoparticle resulting from interference of the incident field and the scattered field from each particle. The strength and spatial aspects of optical binding depend on the polarization of the incident beam [46].…”

“…In fact, as the size of the particles decrease and with a suitable choice of material (e.g. metal) the intense scattering of the trapping field can lead to strong electrodynamic interactions amongst the particles [10,[45][46][47].…”

“…In this article, we introduce and characterize a constant-radius optical vortex that is created by interfering a holographic ring trap using a retro-reflection geometry with a gold (Au) nanoplate mirror [47]. We study the dynamics of single and multiple silver (Ag) nanoparticles driven by the optical vortex to clearly demonstrate OAM transfer from l = −5 to l = 0 to l = +5.…”

Fabrication of a Material Assembly of Silver Nanoparticles Using the Phase Gradients of Optical Tweezers

“…Optical line traps have been used for studying optical binding [2,11,12,15,19]. A typical optical line provides a strongly focused field along the short axis to confine the particles (in 1-D) yet a relatively flat intensity profile along the long axis that facilitates optical binding interactions over many particles.…”