Getman F, Makarenko M, Burguete-Lopez A, Fratalocchi A
PRIMALIGHT, Faculty of Electrical Engineering; Applied Mathematics and Computational Science, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
Light Sci Appl. 2021 Mar 4;10(1):47. doi: 10.1038/s41377-021-00489-7.
Integrating conventional optics into compact nanostructured surfaces is the goal of flat optics. Despite the enormous progress in this technology, there are still critical challenges for real-world applications due to the limited operational efficiency in the visible region, on average lower than 60%, which originates from absorption losses in wavelength-thick (≈ 500 nm) structures. Another issue is the realization of on-demand optical components for controlling vectorial light at visible frequencies simultaneously in both reflection and transmission and with a predetermined wavefront shape. In this work, we developed an inverse design approach that allows the realization of highly efficient (up to 99%) ultrathin (down to 50 nm thick) optics for vectorial light control with broadband input-output responses in the visible and near-IR regions with a desired wavefront shape. The approach leverages suitably engineered semiconductor nanostructures, which behave as a neural network that can approximate a user-defined input-output function. Near-unity performance results from the ultrathin nature of these surfaces, which reduces absorption losses to near-negligible values. Experimentally, we discuss polarizing beam splitters, comparing their performance with the best results obtained from both direct and inverse design techniques, and new flat-optics components represented by dichroic mirrors and the basic unit of a flat-optics display that creates full colours by using only two subpixels, overcoming the limitations of conventional LCD/OLED technologies that require three subpixels for each composite colour. Our devices can be manufactured with a complementary metal-oxide-semiconductor (CMOS)-compatible process, making them scalable for mass production at low cost.
将传统光学器件集成到紧凑的纳米结构表面是平面光学的目标。尽管这项技术取得了巨大进展，但由于在可见光区域的运行效率有限（平均低于60%），这源于波长厚度（约500nm）结构中的吸收损耗，因此在实际应用中仍面临严峻挑战。另一个问题是实现按需光学组件，以便在反射和透射中同时以预定的波前形状控制可见光频率下的矢量光。在这项工作中，我们开发了一种逆向设计方法，该方法能够实现高效（高达99%）的超薄（低至50nm厚）光学器件，用于在可见光和近红外区域控制矢量光，并具有宽带输入-输出响应以及所需的波前形状。该方法利用了经过适当设计的半导体纳米结构，其表现如同一个神经网络，能够近似用户定义的输入-输出函数。接近完美的性能源于这些表面的超薄特性，这将吸收损耗降低到几乎可以忽略不计的值。在实验方面，我们讨论了偏振分束器，将其性能与直接设计和逆向设计技术所取得的最佳结果进行比较，还讨论了以二向色镜和平板光学显示器基本单元为代表的新型平板光学组件，该显示器仅使用两个子像素就能产生全彩，克服了传统液晶显示器/有机发光二极管技术每个合成颜色需要三个子像素的局限性。我们的器件可以通过互补金属氧化物半导体（CMOS）兼容工艺制造，使其能够低成本大规模生产。
