The evolutions of spin density and energy flux of strongly focused standard full Poincaré beams

Nonzero transverse spin density, which describes phenomenon in which the electromagnetic fields of localized light spin in a plane containing its wavenumber vector, has gained enormous interest recently because of its useful applications like spin-direction coupling and routing. In this Letter, using the Richards–Wolf vectorial method for standard full Poincaré beams, we present an analytical model for the high-numerical-aperture focusing system to calculate all components of the electric and magnetic field strength vectors as well as spin density and Poynting vector. The role and contribution of the optical degrees of freedom including ellipticity, handedness, and orientation when the transverse spin density is present, are revealed based on this analytical model. Ellipticity affects the localization and magnitude of the transverse spin density for both transverse and longitudinal components. In contrast, handedness only affects the longitudinal component whereas orientation only affects the transverse component. Furthermore, the energy flux in the focal plane are also studied in detail for the standard full Poincaré beams. These findings may be help in spin-controlled directive coupling and optical tweezers.