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In the framework of Generalized Lorenz–Mie theory (GLMT), based on the expansion results of electromagnetic field radiation components of Bessel pincer light sheets beam acting on dielectric particles of arbitrary size, the expression of radiation force components in a Cartesian coordinate system is obtained by using the Maxwell stress tensor method. On the one hand, the effects of the refractive index and the equivalent radius of spherical particles on the distribution of radiation force are discussed; On the other hand, the influence of beam scaling parameter and beam order of Bessel pincer light sheets beam on the distribution of radiation force are investigated. The results indicate that the changes of particle's refractive index and effective radius only affect the distribution of radiation force. However, the beam scaling parameter and beam order of Bessel pincer light sheets beam have a very sharp impact on the convergence position, distribution range and bending degree far away from the wave source of the radiation force. Single-beam optical tweezers using the self-focusing and self-bending Bessel pincer light-sheets beam are crucial for applications such as single molecule biophysics, optical manipulation and particle separation/clearing. [ABSTRACT FROM AUTHOR]

In the framework of the generalized Lorenz–Mie theory (GLMT), the optical force and torque on a graphene-coated gold nanosphere by a vector Bessel beam are investigated. The core of the particle is gold, whose dielectric function is given by the Drude–Sommerfeld model, and the coating is multilayer graphene with layer number N, whose dielectric function is described by the Lorentz–Drude model. The axial optical force F z and torque T z are numerically analyzed, and the effects of the layer number N, wavelength λ , and beam parameters (half-cone angle α 0 , polarization, and order l) are mainly discussed. Numerical results show that the optical force and torque peaks can be adjusted by increasing the thickness of the graphene coating, and can not be adjusted by changing α 0 and l. However, α 0 and l can change the magnitude of the optical force and torque. The numerical results have potential applications involving the trapped graphene-coated gold nanosphere. [ABSTRACT FROM AUTHOR]

Highlights • The optical force on a charged sphere by a vector Bessel beam is investigated in the framework of GLMT. • The emergence of a pulling force and its dependence on α 0 , order, polarization, and ka are discussed. • The ratios of axial RPCS for charged and neutral spheres are computed to investigate the effect of surface charge. • The optical forces on a relatively small sphere (a = 10 nm) are computed, and the effects of α 0 , order, polarization, and ka are discussed. Abstract Optical tractor beams can reel in an object towards the source, and are becoming a topic of significant worldwide research. Previous works considered the axial and transverse radiation pressure cross-sections (RPCSs) of optical tractor Bessel polarized beams on a dielectric sphere. However, most particles are charged, and it is important to investigate the tractor beam effect on charged particles. The aim of this work is therefore directed toward this goal, where the axial and transverse RPCSs for a charged sphere illuminated by a vector Bessel beam are computed in the framework of generalized Lorenz-Mie theory (GLMT). Numerical computations of the RPCSs are performed, with emphasis on the emergence of a negative pulling force and its dependence on the half-cone angle α 0 , the order l , and the polarization. A higher-order (l ≠ 0) Bessel beam possesses a hollow core and is of vortex nature, while the fundamental mode (l = 0) is of non-vortex type and has a bright maximum intensity at the center of the beam. In our calculation, both l = 0 and l = 1 are considered. The axial PRCSs versus ka and α 0 are first calculated, and the negative axial forces can arise. Moreover, the axial and transverse RPCSs in the plane perpendicular to the beam axis are computed. However, numerical results show that the RPCSs are same to that for a neutral particle. To explain this, the ratios of axial RPCSs for charged and neutral spheres are investigated taking ka as a parameter. The results show that charges only affect the RPCSs for small particles. Finally, the RPCSs for a charged sphere of relatively small are considered. The charge can affect the magnitude of the RPCSs, however, it does not affect the direction of axial optical forces. These results are of great importance in the development of novel optical tweezers and tractor beams. [ABSTRACT FROM AUTHOR]

An analytical description of optical force on a Rayleigh particle by a vector Bessel beam is investigated. Linearly, radially, azimuthally, and circularly polarized Bessel beams are considered. The radial, azimuthal, and axial forces by a vector Bessel beam are numerically simulated. The effect of polarization, order of beams, and half-cone angle to the optical force are mainly discussed. For Bessel beams of larger half-cone angle, the non-paraxiality of beams plays an important role in optical forces. Numerical calculations show that optical forces, especially azimuthal forces, are very sensitive to the polarization of beams. [ABSTRACT FROM AUTHOR]

In this article, we study the optical force exerted on nanorods. In recent years, the capture of micro-nanoparticles has been a frontier topic in optics. A Photonic Jet (PJ) is an emerging subwavelength beam with excellent application prospects. This paper studies the optical force exerted by photonic jets generated by a plane wave illuminating a Generalized Luneburg Lens (GLLs) on nanorods. In the framework of the dipole approximation, the optical force on the nanorods is studied. The electric field of the photonic jet is calculated by the open-source software package DDSCAT developed based on the Discrete Dipole Approximation (DDA). In this paper, the effects of the nanorods' orientation and dielectric constant on the transverse force Fx and longitudinal force Fy are analyzed. Numerical results show that the maximum value of the positive force and the negative force are equal and appear alternately at the position of the photonic jet. Therefore, to capture anisotropic nanoscale-geometries (nanorods), it is necessary to adjust the position of GLLs continuously. It is worth emphasizing that manipulations with nanorods will make it possible to create new materials at the nanoscale. [ABSTRACT FROM AUTHOR]

• Optical force on a sphere of arbitrary size illuminated by an Airy lightsheet is investigated using GLMT. • The BSCs of the Airy light-sheet are calculated using ASDM and VSWFs. • The negative longitudinal optical force is particularly emphasized. • The two kinds of polarizations (TE and TM) of Airy light-sheet are discussed. • The influences of the transverse scale parameter ω 0 and attenuation parameter γ of the Airy light-sheet are discussed. Based on the generalized Lorenz–Mie theory (GLMT) and the angular spectrum decomposition method (ASDM), we calculate the optical radiation force exerted on a lossless dielectric sphere of arbitrary size illuminated by an Airy light-sheet. The beam shape coefficients (BSCs) of the Airy light-sheet are calculated using the vector angular spectrum decomposition and vector spherical wave functions methods. The optical radiation force acting on the spherical particle is obtained by the integral of Maxwell's stress tensor. The transverse (F y) and longitudinal (F z) forces are numerically computed. Two kinds of polarization (TE and TM) are considered for the Airy light-sheet, and the negative longitudinal optical (pulling) force is particularly emphasized. The influence of the transverse scale parameter w 0 and attenuation parameter γ of the Airy light-sheet on the force is discussed. The results of the present theory are verified using the dipole approximation method in which the gradient force has been also computed for a Rayleigh sphere. The numerical results show that when the transverse scale parameter w 0 and attenuation parameter γ increase, the transverse and longitudinal forces decrease. Furthermore, the force caustic (i.e., maximum) shifts to the direction of y < 0 as the transverse scale parameter w 0 increases. As the dimensionless size parameter of the sphere ka increases (where k is the wavenumber and a is the radius), the resonance peaks of the optical forces become larger. The results of this paper are of practical significance for the development of Airy light-sheet based optical manipulation technologies. [ABSTRACT FROM AUTHOR]