Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, 84112, USA.
Sci Rep. 2017 Jul 19;7(1):5789. doi: 10.1038/s41598-017-06229-5.
We show that multi-level diffractive microstructures can enable broadband, on-axis transmissive holograms that can project complex full-color images, which are invariant to viewing angle. Compared to alternatives like metaholograms, diffractive holograms utilize much larger minimum features (>10 µm), much smaller aspect ratios (<0.2) and thereby, can be fabricated in a single lithography step over relatively large areas (>30 mm ×30 mm). We designed, fabricated and characterized holograms that encode various full-color images. Our devices demonstrate absolute transmission efficiencies of >86% across the visible spectrum from 405 nm to 633 nm (peak value of about 92%), and excellent color fidelity. Furthermore, these devices do not exhibit polarization dependence. Finally, we emphasize that our devices exhibit negligible absorption and are phase-only holograms with high diffraction efficiency.
我们展示了多层衍射微结构能够实现宽带、同轴透射式全息图，能够投影复杂的全彩色图像，并且对视角不变。与元全息图等替代方案相比，衍射全息图利用了更大的最小特征（>10μm），更小的纵横比（<0.2），因此可以在相对较大的区域（>30mm×30mm）上通过单次光刻步骤制造。我们设计、制造和表征了编码各种全彩色图像的全息图。我们的器件在 405nm 至 633nm 的可见光谱范围内实现了>86%的绝对透过率（峰值约为 92%），并且具有出色的色彩保真度。此外，这些器件没有表现出偏振依赖性。最后，我们强调我们的器件具有可以忽略的吸收和高衍射效率的纯相位全息图。
