Dynamic of Si nanoparticles inside of a quadrupolar trap: Analysis of the angular momentum transfer

Luis Carretero,Pablo Acebal,Salvador Blaya,Manuel Pérez-Molina

doi:10.1016/j.rinp.2020.103520

Luis Carretero, Pablo Acebal + Show 2 more

Open Access

https://doi.org/10.1016/j.rinp.2020.103520

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Abstract

We investigate the dynamics of Si spherical nanoparticles for different infrared wavelengths in a system based on two circularly polarized counter-propagating Gaussian beams. Through the analysis of the dipolar and quadrupolar forces, we obtain several conditions under which these nanoparticles describe different types of attractive or repulsive spirals at focus plane depending on the efficiency of the quadrupole trap obtained. We demonstrate that these spirals are generated by the angular momentum transfer from the electromagnetic field to the particles, and this is mainly due to the interference forces dipole–dipole and quadrupole–dipole. Through the adequate selection of the wavelength, angular momentum transfer can only take place with quadrupolar–dipolar interference forces. We study particle dynamics by solving the deterministic and non-deterministic over-damped Langevin equation.

Highlights

The study of silicon nanoparticles is an important topic in the field of photonics and optics because such particles present high resonances with low dissipation levels, are biologically compatible and can be produced at low cost [1]
We study the dynamics of Si nanoparticles inside an infrared quadrupolar optical trap by solving the Langevin equation
The dynamic of Si nanoparticles in a quadrupolar optical trap have been analyzed for different wavelengths in the infrared region

Summary

Introduction

The study of silicon nanoparticles is an important topic in the field of photonics and optics because such particles present high resonances with low dissipation levels, are biologically compatible and can be produced at low cost [1]. Previous angular momentum transfer studies were analyzed in a framework where the interaction of dipole with electromagnetic field explained the theoretical and experimental results. Another very important and deeper review that covers the majority of optical force mechanisms from a theoretical and experimental point of view can be found in [17]. The importance of multipole excitations [26] has been pointed out in different papers, where the following have been analyzed: the optical pulling force produced by the interference of the radiation multipoles [27], resonant electromagnetic dipole–quadrupole coupling in nanoparticle arrays [28] or the angular momentum transfer between a quadrupole emitter and a dipole acceptor [29]. We analyze the angular momentum transfer from the electromagnetic field to mechanical angular momentum of Si nanoparticles mainly via the interference forces of dipole–dipole and quadrupole–dipole radiation

Theory

Particle dynamics

Numerical examples

Conclusion