Apodized multilevel diffractive lenses that produce desired diffraction-limited focal spots.
An apodized, multilevel diffractive lens that can produce a desired diffraction-limited focal spot is proposed for many applications, such as focusing, imaging, optical storage, and optical trapping. The three key points for the design are the innovative idea of complex conjugate subzones, the use of Babinet's principle, and the equivalent-pupil (or aperture) function theory of diffractive focusing elements composed of concentric transparent rings. As a concrete example, we numerically design a mixed multilevel diffractive lens (the highest phase level is 8) to produce a diffraction-limited Gaussian focal spot. Some related problems, such as the validity range and the combination with high-numerical-aperture refractive lenses, are also discussed.
Optische Nachrichtentechnik, FernUniversität Hagen, Universitätsstrasse 27/PRG, 58084 Hagen, Germany. qing.cao@fernuni-hagen.de
Qing
Q
Cao
Jürgen
J
Jahns