Tailoring focal plane component intensities of polarization singular fields in a tight focusing system

Abstract

Abstract The scientific community studies tight focusing of radially and azimuthally-polarized vector beams as it is a versatile solution for many applications. We offer a new method to produce tight focusing that ensures a more uniform intensity profile in multiple dimensions, providing a more versatile and stable solution. We manipulate the polarization of the radially and azimuthally polarized vector beams to find an optimal operating point. We examine in detail optical fields whose polarization states lie on the equator of the relevant Poincaré spheres namely, the fundamental Poincaré sphere, the hybrid order Poincaré sphere (HyOPS), and the higher order Poincaré sphere. We find via simulation that the fields falling on these equators have focal plane intensity distributions characterized by a single rotation parameter $$\alpha$$ α determining the individual state of polarization. The strengths of the component field distributions vary with $$\alpha$$ α and can be tuned to achieve equal strengths of longitudinal (z) and transverse (x and y) components at the focal plane. Without control of this parameter (e.g., using $$\alpha =0$$ α = 0 in radially and $$\alpha =\pi$$ α = π in azimuthally-polarized vector beams) intensity in x and y components are at 20% of the z component. In our solution with $$\alpha =\pi /2$$ α = π / 2 , all components are at 80% of the maximum possible intensity of z. In examining the impact of $$\alpha$$ α on a tightly focused beam, we also found that a helicity inversion of HyOPS beams causes a rotation of 180 degree in the axial intensity distribution.