CAREER: Photonic Integrated Guided-Wave-Driven Metasurfaces

像电子电路一样，集成光子学在芯片上布线光，为计算和通信系统对数据传输带宽和能源效率的日益增长的需求提供了一个有前途的长期解决方案。光子集成电路（PIC）将许多光控元件组合到单个芯片中，类似于彻底改变电子工业的互补金属氧化物半导体（CMOS）芯片，在速度、带宽、可靠性、可扩展性、功耗等方面具有很大优势。为了充分利用PICs在自由空间应用中的优势，当光在引导模式和自由空间模式之间转换时，具有灵活控制光的接口至关重要。然而，传统的耦合技术，如边缘耦合器和表面光栅，功能有限，缺乏完全控制光的能力。虽然光栅阵列可以实现更高级的功能，如片外光束转向、聚焦和全息图像构建，但由于存在高阶衍射，它们占地面积大，并且存在损耗。因此，迫切需要一种统一的方法来实现PICs上复杂的自由空间光学功能。该计划的主要目标是开发一种混合结构，其中超表面-超薄人造表面通过工程亚波长结构（也称为元原子）通过局部施加光学特性的突变来操纵光-直接由导波驱动以实现复杂的自由空间功能。该计划将包括紧密结合的教育活动（如开发纳米光子学的新课程），旨在通过让本科生和研究生接触纳米光子学器件的令人兴奋的发展来解决光学计算，通信和网络方面的重要社会问题，从而刺激他们追求工程事业。此外，纳米光子云计算工具将被开发出来，可以在网络浏览器中免费运行，而不需要强大的工作站，这将特别有利于全球经济上处于劣势的研究社区。此外，我们还会举办一些外展活动，例如举办有趣的光学效果展览，以提高K-12师生在当地学校和公共图书馆的兴趣和参与度。本研究计划的总体目标是结合两种强大的互补技术-集成光子学和超表面-共同开发一种新的架构，其中超表面直接由PICs中的导波驱动，以实现复杂的光学功能。尺寸远小于光学波长的元原子构建块将被放置在光子集成元件的顶部。通过由这些元原子组成的超表面，引导光可以在自由空间或光子晶体中被塑造成任何所需的复杂光场。本研究将建立理论、设计、材料合成、器件纳米制造平台，为完全光控提供完整的光子集成路径。所提出的混合架构将提供巨大的好处：(1)由PICs中的导波直接驱动的超表面；(2)光可以传输到不同的超表面，在单个波导上执行多种复杂功能；(3) pic现在具有控制亚波长尺度的光的能力。该技术将为构建具有灵活访问自由空间的多功能光子集成器件铺平新的令人兴奋的道路，并导致大量新颖应用，特别是在系统尺寸，重量，功率和性能方面的重大挑战。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Wiring light on a chip like electronic circuits, integrated photonics provides a promising long-term solution for increasing demands for data transmission bandwidth and energy efficiency of computing and communication systems. A photonic integrated circuit (PIC) combining many light-controlling components into a single chip, similar to complementary metal oxide semiconductor (CMOS) chips that have revolutionized the electronics industry, offers great advantages in terms of speed, bandwidth, reliability, scalability, power consumption, and etc. In order to fully exploit the benefits of PICs in free-space applications, it is crucial to have an interface that can flexibly control light when it converts between guided and free-space modes. However, conventional coupling techniques such as edge couplers and surface gratings have limited functionalities and lack of the capability to complete control over light. Although arrays of gratings can achieve more advanced functions, such as off-chip beam steering, focusing, and holographic image construction, they have large footprints and suffer from loss due to the existence of high-order diffractions. Therefore, there is a strong demand for a unified approach to achieve complex free-space optical functions on PICs. The major goal of the proposed program is to develop a hybrid architecture where metasurfaces – ultrathin artificial surfaces which manipulate light by locally imposing abrupt changes to optical properties through engineered sub-wavelength structures also known as meta-atoms – are directly driven by guided waves to realize complex free-space functions. The proposed program will include closely integrated educational activities (such as developing a new course on nanophotonics) designed to stimulate undergraduate and graduate students to pursue engineering career by exposing them to the exciting development of nanophotonic devices solving important societal problems in optical computing, communication, and networking. Besides, nanophotonic cloud computing tools will be developed that are free-to-run in web browsers without the need for powerful workstations that will be especially beneficial for economically disadvantaged research communities worldwide. Furthermore, outreach activities, such as organizing fun exhibitions of optics effects, will also be provided to promote the interests and participations of K-12 teachers and students in local schools and public libraries.The overarching goal of this research program is to combine two powerful, complimentary technologies – the integrated photonics and the metasurface – together to develop a new architecture where metasurfaces are directly driven by the guided waves in PICs for realizing complex optical functions. The meta-atom building blocks with sizes much smaller than the optical wavelength will be placed on top of photonic integrated components. Through the metasurfaces consisting of such meta-atoms, the guided light can be molded to any desired complex light fields in free space or in PICs. The proposed research will establish a theory, design, material synthesis, and device nanofabrication platform and provide a complete photonic integrated route for complete light control. Tremendous benefits will be offered by the proposed hybrid architecture: (1) metasurfaces that are driven directly by guided waves in PICs; (2) light can be routed to different metasurfaces performing multiple complex functions on a single waveguide; and (3) PICs are now empowered with the ability to control light at the subwavelength scale. The technology will pave new exciting ways for building multifunctional photonic integrated devices with flexible access to free space and lead to a large spectrum of novel applications particularly where the grand challenges of the system size, weight, and power, performance are concerned.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.