Focusing light to a tighter spot

The smallest spot sizes are reached by focusing an annular shaped light bea m with a high aperture lens, We show theoretically that the focal area is f urther reduced when using a novel radially polarized instead of a linearly polarized light annulus. In the vicinity of the focus there is a large long itudinally polarized field component [1] which is still narrower and has no pronounced side lobes. A special photosensitive layer prepared to be sensi tive only to this longitudinal field component may be used to reach an even smaller focal area, 0.1 lambda(2), which is determined by the contour of t he intensity distribution at half the maximum value. The radially polarized doughnut mode may also be used to build improved near field sensors having a substantially increased brightness. (C) 2000 Elsevier Science B.V. All r ights reserved.