Optical Force and Torque on a Graphene-Coated Gold Nanosphere by a Vector Bessel Beam

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 Fz and torque Tz are numerically analyzed, and the
effects of the layer number N, wavelength λ, and beam parameters (half-cone angle α0, 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
α0 and l. However, α0 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.