Forming light beams and patterns with zero intensity central points

摘要

In order to produce a beam with a zero intensity axial ray or to produce a beam that when focused will produce an image of a doughnut shaped pattern with a zero intensity central point, a beam with a uniform or Gaussian profile is directed to a plurality of transparent plates, arranged in pairs on opposite sides of the beam axis, such that for at least one pair, the plates have a composition and thickness different from each other, and chosen so that the transmitted light has a phase difference of half a wavelength for at least three different wavelengths. An additional plate with a center on the perpendicular of the line connecting the first two plates has a composition and thickness such that the light transmitted through that additional plate has a phase difference of a quarter wavelength with respect to the light transmitted through one of the plates of said first pair of plates, at at least one wavelength.

主权项

1. A device for shaping a light beam to have an intensity distribution having at least one point of substantially zero intensity, said device having a beam axis, the device comprising a plurality of transparent plates of varying thickness, wherein said plates are disposed substantially in a plane, so that said plates are arrayed in relation to said axis, so that different portions of said beam pass through different transparent plates, wherein a first transparent plate has a first composition and wherein a second transparent plate has a second composition different from the first composition of the first transparent plate, and wherein said compositions and thicknesses of said plates are chosen such that at any wavelength in a wavelength range of at least several tens of nanometers said beam portions experience particular phase delays in passing through their corresponding plates, such that said particular phase delays cause said beam portions to interfere at said at least one point to produce a substantially zero intensity.