Reduction of focal-spot size using dichromats in absorbance modulation.

We experimentally verify the focusing characteristics of dichromats, a new class of circular-symmetric diffractive-optical lenses that generate, in the same focal plane, focal spots for one wavelength and ring-shaped spots with central nodes for another wavelength. Using a dichromat, we illuminate a thin photochromic layer and demonstrated point-spread-function compression of the transmitted focal spot.