Sharper Focus for a Radially Polarized Light Beam

We experimentally demonstrate for the first time that a radially polarized field can be focused to a spot size significantly smaller 0.16(1)lambda(2) than for linear polarization (0.26lambda(2)). The effect of the vector properties of light is shown by a comparison of the focal intensity distribution for radially and azimuthally polarized input fields. For strong focusing, a radially polarized field leads to a longitudinal electric field component at the focus which is sharp and centered at the optical axis. The relative contribution of this component is enhanced by using an annular aperture.