Harnessing optical nonlinearity to control reversal of trapping force under pulsed excitation: a theoretical investigation

Abstract

The dramatic influence of optical Kerr effect on the nature of trapping force/potential under pulsed excitation has recently been explored, particularly in the context of trapping of dielectric nanoparticles (Devi and De 2016 Opt. Express 24 21485–96, Devi and De 2017 Phys. Rev. A 96 023856). However, the utility of such effect has yet to be fully understood, which we discuss here. For a variety of nanoparticles (core, core/shell, and hollow-core), we theoretically show how optical force/potential depend on the nature of the material under pulsed excitation and, most importantly, how the force/potential reverses from repulsive to attractive for certain hollow-core nanoparticles made of high nonlinear refractive index material.

Enhanced optical force on mutilayered dielectric nanoparticles: Tuning material properties and nature of excitation

“…However, the presence of 2 nm CdS layer in-between the hollow-polystyrene nanoparticle allows the particle to experience an attractive force under similar excitation conditions. As mentioned earlier, the reversal nature of force (from repulsive to attractive) was shown for hollow-core nanoparticles upon changing the excitation from CW to pulsed (owing to the effect of OKE) [14][15][16]. In contrast, for a hollow core-shell-shell type nanoparticles, even under CW excitation such a reversal in the nature of the force is observed; note that similar reversal under CW excitation was also observed for hollow-core type nanoparticles by tuning the thickness of the material [16].…”

“…In recent work, we theoretically demonstrated enhanced trapping efficiency for core-shell type nanoparticles over bare which was further shown to be finetuned by optical nonlinearity under pulsed excitation [14]. Also, a reversal (from repulsive to attractive) in optical trapping force under pulsed excitation [14][15][16]. However, due to the larger tuneability of effective polarizability by the thickness of layers of multilayered nanoparticles are promised to offer better trapping efficiency.…”

Enhanced optical force on multilayered dielectric nanoparticles by tuning material properties and nature of excitation: a theoretical investigation

“…As mentioned earlier, the reversal nature of force (from repulsive to attractive) was shown for hollow-core nanoparticles upon changing the excitation from CW to pulsed (owing to the effect of OKE). 14–16 In contrast, for a hollow core–shell–shell type nanoparticles, even under CW excitation such a reversal in the nature of the force is observed; note that similar reversal under CW excitation was also observed for hollow-core type nanoparticles by tuning the thickness of the material. 16 Under pulsed excitation, owing to the OKE, both hollow-polystyrene and hollow-CdS–polystyrene nanoparticles experience an attractive force.…”

“…14 Also, a reversal (from repulsive to attractive) in optical trapping force under pulsed excitation was reported. [14][15][16] However, due to the facile tuneability of effective polarizability by changing the thickness of layers of multilayered nanoparticles are promised to offer better trapping efficiency.…”

Controlling optical trapping of metal–dielectric hybrid nanoparticles under ultrafast pulsed excitation: a theoretical investigation

“…39 In previous studies, the advantage of using pulsed excitation to reverse the direction of trapping of hollow dielectric particles was theoretically shown. 34,35 Fig. 7 shows the trapping force/potential along the axial direction, compared among conventional (silver) and hollow-core silver nanoparticles at 100 mW average power for xed NA 1.4 under both CW and pulsed excitation.…”