High-Density Photonic Chip Integration with Extreme Skin-Depth Waveguides

非技术性：芯片级光子器件可以将大体积光学系统集成到单个微小芯片中，使其便携并允许实验室外的各种光学应用。光子芯片与电子电路的集成也可以导致广泛的应用，例如，在高速光通信，化学和生物传感，高精度光谱学，以及无人驾驶汽车的光检测和测距。随着电子器件在支持高密度集成电路方面发生了革命性的变化，在许多光学应用中非常需要增加光子芯片集成密度;它在芯片中提供更多的功能和更低的功耗。然而，由于光的波动性质，高密度光子芯片集成是极其困难的，并且当前的方法依赖于复合半导体材料的折射率对比度。德克萨斯理工大学的研究将探索一种使用全介电和高度各向异性超材料的替代方法，即人工设计的人造材料，以提高光子芯片的集成密度。拟议的研究将在单片绝缘体上硅晶片上实施，该晶片与当前的半导体代工工艺兼容，并提供低成本的解决方案;因此，这项研究也将在工业中产生更广泛的影响，加速光子芯片在许多应用中的实际使用。教育和推广活动是该项目的重中之重，将为本科生和研究生，特别是代表性不足的学生群体提供实践经验。技术：实现高密度光子芯片集成在许多应用中都是非常需要的，因为更多的构建块在单个芯片上提供更多的功能（类似于电子产品）。然而，目前的光限制方法依赖于芯和包层材料的折射率对比，并且光子器件的进一步小型化受到光的波动性质的阻碍，即，包层中的倏逝波引起波导串扰。本计画的目标是有效地抑制光波导的串音，并设计与实现超小型的晶片上光子元件与电路。本计画将借由极端趋肤深度波导中特殊耦合现象的基本分析与实验验证，来达成此目标。将探索极端趋肤深度波导中的各向异性耦合机制以从根本上理解这种现象，并将在硅芯片上实验证明具有低串扰的超长耦合长度。特殊耦合的制造公差也将被评估，所有的表征结果将与数值和分析结果进行比较。该项目还将探索有源介质在各向异性包层中的作用，并将利用各向异性超材料实现各种无源和有源超紧凑光子器件。该项目的成果将科学地揭示一种特殊耦合的基本机制，这种耦合可以抑制光学串扰，并通过在芯片上提供更多功能，在技术上推进光子应用。该奖项反映了NSF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。

Nontechnical: Chip-scale photonic devices can miniaturize a bulk optical system into a single tiny chip, making it portable and allowing various optical applications outside of the laboratory. The integration of photonic chips with electronic circuitry can also lead to a broad range of applications, for example, in high-speed optical communication, chemical- and bio-sensing, high-precision spectroscopy, and light detection and ranging for driverless automobiles. As electronic devices have been revolutionized in support of high-density integrated circuits, increasing the photonic chip integration density is highly desired in many optical applications; it offers more functionality and lower power consumption in a chip. However, due to the wave nature of light, high-density photonic chip integration is extremely difficult, and the current approach relies on the index-contrast of composite semiconductor materials. Research at Texas Tech University will explore an alternative approach of using all-dielectric and highly anisotropic metamaterials, i.e. artificially engineered man-made materials, to increase the photonic chip integration density. The proposed research will be implemented on a monolithic silicon-on-insulator wafer, which is compatible with the current semiconductor foundry process and provides a low-cost solution; thus, this research would have a broader impact in industry as well, accelerating the practical use of photonic chips in many applications. Educational and outreach activities are a high priority of this project and will provide hands-on experiences for undergraduate and graduate students, especially underrepresented groups of students.Technical: Realizing a high-density photonic chip integration is highly desired in many applications, as more building blocks provide more functionalities on a single chip (analogous to electronics). However, current approaches of light confinement rely on the index-contrast of core and cladding materials and further miniaturization of photonic devices is hampered by the wave nature of light, i.e., the evanescent wave in the cladding causes waveguide crosstalk. The goal of this project is to suppress the waveguide crosstalk significantly and to devise and implement ultracompact on-chip photonic devices and circuitry. This project will pursue this goal through fundamental analysis and experimental demonstration of the exceptional coupling phenomena in the extreme skin-depth waveguides. An anisotropic coupling mechanism in the extreme skin-depth waveguides will be explored to fundamentally understand the phenomena and extremely long coupling lengths with low crosstalk will be experimentally demonstrated on a silicon chip. The fabrication tolerance of the exceptional coupling will be assessed as well, and all the characterization results will be compared with numerical and analytical results. The project will also explore the effect of active media in anisotropic claddings and will implement various passive and active ultracompact photonic devices with anisotropic metamaterials. The outcomes of this project will scientifically reveal the fundamental mechanism of an exceptional coupling that can suppress optical crosstalk and will technically advance photonic applications by providing more functionalities on a chip.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.