We have developed a method for encoding phase and amplitude in microscopic computer-generated holograms (microtags) for security applications. An 8 × 8 cell phase-only and an 8 × 8 cell phase-and-amplitude microtag design has been exposed in photoresist by the extreme-ultraviolet (13.4-nm) lithography tool developed at Sandia National Laboratories. Each microtag measures 80 μm × 160 μm and contains features that are 0.2 μm wide. Fraunhofer zone diffraction patterns can be obtained from fabricated microtags without any intervening optics and compare favorably with predicted diffraction patterns.
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