Compact Phase-Modulated Photonic Structures for On-Chip Multiband Spectroscopy

由于高度集成的光子学和量子通信技术的快速发展以及最近高分辨率医学成像技术的进步，目前迫切需要能够同时对不同光谱带进行光聚焦和方向控制的小型化和可伸缩的光学元件。作为对这些挑战的回应，该项目推动了人们对在纳米尺度上结合多种功能的光学设备的理解。研究团队利用实验和计算方法帮助开发新的材料和结构，以实现可控的光聚焦响应，降低损耗并提高效率，用于下一代高能效纳米光子学设备，如芯片上光谱仪、光学传感器和在多个和光谱区域运行的微型成像系统。该项目支持一名研究生，并通过一个充满活力的外展计划鼓励本科生参与研究，该计划旨在通过波士顿大学的暑期项目与实际实验室演示和研究活动合作，在他们的学术课程中介绍光学科学和工程的基本概念。这一推广计划的一个重要组成部分是通过参与该项目，吸引代表人数不足的少数群体投身光学工程事业。最后，作为波士顿大学光子学推广计划的一部分，将向学生(研究生和本科生)以及工业界和学术界的实践者提供针对新兴超光子学领域的重点教学模块。该计划的主要目标是结合偏光学和衍射光学技术的优点，以设计、制造和实验表征基于高折射率透明材料和可扩展多能级制造的空间调制相位分布的高性能、超紧凑的新型衍射器件。特别是，研究人员将专注于两种密切相关的新型光子结构：(I)基于具有工程相位调制的消色差轴向透镜的单元件、超紧凑微型光谱仪，以及(Ii)基于多光谱轴向透镜的聚焦装置，其实现了辐射在选定光谱波段上的同时聚焦。这些目标将通过将严格的瑞利-索末菲衍射理论、设备级有限元数值设计、材料制造以及具有广泛光谱范围内集成成像和光谱功能的光学设备的实验表征的综合集成来实现。虽然在可见光和近红外(NIR)光谱范围内使用硅(Si)和二氧化钛(Ti02)透明介质，但研究概念、方法和设计途径可以自然地扩展到任何感兴趣的波长和介电材料平台。拟议研究计划的智力优势依赖于开发新的、更强大的途径，以开发具有成本效益的、小型化的相位工程器件，这些器件对偏振不敏感，可在大范围的入射角度下工作，并结合高效的聚焦和光栅响应，除了光学光谱学外，还可应用于多光谱光学检测、量子信息源和芯片传感。该项目能够产生更广泛的影响，因为它为下一代用于光学成像、传感和光谱分析的超紧凑型光谱相位调制设备奠定了基础。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Due to the rapid developments of highly-integrated photonics and quantum communication technologies as well as the recent advancements of high-resolution medical imaging techniques, there is currently a compelling need for miniaturized and scalable optical elements that enable simultaneous light focusing and directional control over different spectral bands. Responding to these challenges, this project advances the understanding of optical devices that combine multiple functionalities on the nanoscale. The research team utilizes experimental and computational approaches to help develop novel materials and structures that enable controllable light focusing responses with reduced losses and enhanced efficiency for use in next generation of power-efficient nanophotonics devices, such as on-chip spectrometers, optical sensors, and miniaturized imaging systems that operate over multiple and spectral regions. The project supports one graduate student and encourages the involvement of undergraduate students in the research through a vibrant outreach program aimed at introducing fundamental concepts of optical science and engineering in their academic curricula in partnership with practical laboratory demonstrations and research activities through summer programs at Boston University. An important component of this outreach plan is to attract underrepresented minorities to a career in optical engineering through participation in the project. Finally, the outreach involves the development of a focused teaching module addressing the emerging field of Metaphotonics that will be offered to students (graduate and undergraduate) and practitioners both in industry and academia as part of the photonics outreach programs at Boston University.The primary goal of this proposal is to combine favorable aspects from both meta-optics and diffractive optics technologies in order to design, fabricate, and experimentally characterize high-performance, ultra-compact novel diffractive devices with spatially-modulated phase profiles based on high-index transparent materials and scalable multi-level fabrication. In particular, the researchers will focus on two closely related novel photonic structures: (i) single-element, ultra-compact micro- spectrometers based on achromatic axilenses with engineered phase modulation, and (ii) multi-spectral axilens-based focusing devices that achieve simultaneous focusing of radiation over selected spectral bands. The goals will be accomplished by a comprehensive integration of rigorous Rayleigh-Sommerfeld diffraction theory, device-level Finite Element Method (FEM) numerical design, materials fabrication, and experimental characterization of optical devices with integrated imaging and spectroscopic functionalities across a wide spectral range. While using silicon (Si) and titanium dioxide (TiO2) transparent dielectrics for the visible and near-infrared (NIR) spectral range, the research concepts, methods and design approach can naturally be extended to any wavelength of interest and dielectric materials platforms. The intellectual merit of the proposed research program relies on the development of novel and more powerful avenues for cost-effective, miniaturized, phase-engineered devices that are polarization insensitive, work over a large range of incidence angles, and combine highly-efficient focusing and grating responses that, in addition to optical spectroscopy, also find applications to multi- spectral optical detection, quantum information sources, and on-chip sensing. This project enables a substantial broader impact as it provides the foundation for the next generation of ultra-compact spectroscopic phase-modulated devices for optical imaging, sensing, and spectroscopy.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.