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Abstract Transversally sharply structured optical fields are discussed, which rotate upon propagation without any lateral expansion of the intensity profile. Finite-aperture approximations of such fields, realizable with phase-only and complex-amplitude recording, are demonstrated. Recording of at least some of the amplitude information (rather than neglecting it completely) is shown to improve the field quality considerably, in particular close to the element. Lohmann-coded binary-phase diffractive elements with restricted amplitude recording are fabricated by electron beam lithography and reactive ion etching. The experimental results are in good agreement with theory.
Pääkkönen et al. (Sun,) studied this question.