Plasmonic Cube Tetramers over Substrates: Reversal of Binding Force as the Effect of Fano Resonance and Light Polarization

Abstract

Near-field optical binding force is an emerging new topic in the field of optical manipulation and plasmonics. However, so far, all the studies of near-field binding force and its counterintuitive reversal are only restricted to dimer sets. In this work, we have studied extensively the idea of near-field optical binding force and associated Lorentz force dynamics for more than two objects, such as plasmonic tetramers over different substrates. We have demonstrated that if closely positioned plasmonic cube tetramers are placed only over the plasmonic substrate and the circularly polarized light is impinged over them, all-optical control between their mutual attraction and repulsion is possible because of strong Fano resonance. In addition, the polarization state of light controls the shifting of the extinction spectra and the binding force reversal wavelength, making such nanostructures ideal for the polarization-dependent optical switching device. The high magnitude of attractive and repulsive binding forces has been obtained at the dark and bright resonant modes, respectively, because of strong induced currents in the plasmonic substrate. Because of its simple arrangement, our proposed tetramer configuration may open a novel route for all-optical particle clustering, aggregation, and crystallization, which can be verified by the simple experimental setup.

Dielectric or plasmonic Mie object at air–liquid interface: The transferred and the traveling momenta of photon*

“…It is well known that Minkowski stress tensor [37][38][39][40][41][46][47][48] has a divergence free nature, which suggests that, if the Minkowski stress tensor is applied inside a non-absorbing object employing the internal field of the embedded object, it would lead to zero time-averaged total force. When absorption is introduced inside the half-immersed object, the force inside the absorbing object has a non-zero value equal to Eq.…”

“…Let us consider a lossless magneto-dielectric slab of sides at z = 0 and z = d, embedded (fully immersed) in a magnetodielectric medium, illuminated at normal incidence by a linearly polarized plane wave propagating along the z direction with time harmonic dependence e i(kz−ωt) . There is an interesting alternative way to calculate the time averaged force known as Lorentz force [46][47][48] f Bulk…”

“…8(b)] and surface force method. [15,35,46,47] The total momentum conservation equation for the Lorentz volumetric force (whatever the form is chosen [54,55] ) leads to the Abraham momentum of photon [cf. supplement s3 for detail analysis]…”

Wavelength-Dependent Optical Force Aggregation of Gold Nanorods for SERS in a Microfluidic Chip

“…58,61 Using this approach, single-molecule sensitivity has been shown toward resonant molecules of rhodamine 6G/ Nile blue mixtures, 61 a pM sensitivity in the resonant detection of hemoglobin, 56 and down to 50 nM to nonresonant bovine serum albumin (BSA) molecules. 55 A plasmonic enhancement of the optical forces has been observed in the trapping of colloidal aggregates, 43 whereas the role of the plasmon resonances in the optical pushing and aggregation process is not fully elucidated as both optical binding 64,65 and thermal effects 55 might play a role in the aggregation process. In this article, we investigate the aggregation dynamics of bovine serum albumin (BSA) and gold nanorod (AuNR) complexes as a function of wavelength and power.…”

“…A plasmonic enhancement of the optical forces has been observed in the trapping of colloidal aggregates, whereas the role of the plasmon resonances in the optical pushing and aggregation process is not fully elucidated as both optical binding , and thermal effects might play a role in the aggregation process. In this article, we investigate the aggregation dynamics of bovine serum albumin (BSA) and gold nanorod (AuNR) complexes as a function of wavelength and power.…”