Toward a spherical spot distribution with 4pi focusing of radially polarized light

Opt Lett. 2004 Sep 1;29(17):1968-70. doi: 10.1364/ol.29.001968.


The properties of the focal spot for 4pi focusing with radially polarized light are presented for various apodization factors. With a focusing system satisfying the Herschel condition, sharp focal spots with almost-perfect spherical symmetry (leading to equal axial and transverse resolution) and extremely low sidelobes are achieved.