Journal of the Optical Society of America A: Optics and Image Science, and Vision

Experimental characterization of focusing by high-numerical-aperture zone plates

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High-numerical-aperture zone plates have important applications in high-resolution optical maskless lithography as well as scanning confocal microscopy. We describe two methods to experimentally characterize the focusing properties, i.e., the point-spread function, of such diffractive lenses. The first method uses spot exposures in photoresist and the second uses a conventional knife-edge scan. The experimental results agree well with rigorous theoretical calculations. © 2006 Optical Society of America.