Tunable longitudinal spin–orbit separation of complex vector modes

Abstract

Complex vector modes are opening burgeoning opportunities for a wide variety of applications and therefore the flexible manipulation of their various properties has become a topic of late. As such, in this Letter, we demonstrate a longitudinal spin–orbit separation of complex vector modes propagating in free space. To achieve this, we employed the recently demonstrated circular Airy Gaussian vortex vector (CAGVV) modes, which feature a self-focusing property. More precisely, by properly manipulating the intrinsic parameters of CAGVV modes, the strong coupling between the two constituting orthogonal components can be engineered to undergo a spin–orbit separation along the propagation direction. In other words, while one polarization component focuses at one plane, the other focuses at a different plane. Such spin–orbit separation, which we demonstrated by numerical simulations and corroborated experimentally, can be adjusted on-demand by simply changing the initial parameters of the CAGVV mode. Our findings will be of great relevance in applications such as optical tweezers, to manipulate micro- or nano-particles at two different parallel planes.