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高分辨率医学成像技术的最新进展，目前迫切需要小型化和可扩展的光学元件，以便在不同的光谱波段上同时进行光聚焦和方向控制。为了应对这些挑战，该项目推进了对纳米尺度上结合多种功能的光学器件的理解。该研究团队利用实验和计算方法来帮助开发新型材料和结构，这些材料和结构可以实现可控的光聚焦响应，减少损耗，提高效率，用于下一代节能纳米光子学设备，如片上光谱仪、光学传感器和在多个光谱区域操作的小型化成像系统。该项目支持一名研究生，并鼓励本科生参与研究，通过一个充满活力的推广项目，旨在将光学科学和工程的基本概念引入学术课程，并通过波士顿大学的暑期项目进行实际的实验室演示和研究活动。该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性不足的少数民族从事光学工程事业。最后，作为波士顿大学光子学外展项目的一部分，该外展涉及到一个重点教学模块的开发，该模块将提供给学生（研究生和本科生）以及工业界和学术界的从业者。本提案的主要目标是结合元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的多级制造的具有空间调制相位轮廓的高性能、超紧凑的新型衍射器件。研究人员将特别关注两种密切相关的新型光子结构：(i)基于消色差轴透镜的单元件超紧凑微型光谱仪，采用工程相位调制；（ii）基于多光谱轴透镜的聚焦装置，在选定的光谱带上实现辐射的同时聚焦。目标将通过严格的Rayleigh-Sommerfeld衍射理论、器件级有限元方法（FEM）数值设计、材料制造和光学器件的实验特性的综合集成来实现，这些光学器件具有广泛的光谱范围内的集成成像和光谱功能。在可见光和近红外（NIR）光谱范围内使用硅（Si）和二氧化钛（TiO2）透明介质的同时，研究概念、方法和设计方法自然可以扩展到任何感兴趣的波长和介质材料平台。提出的研究计划的智力价值依赖于开发新颖和更强大的途径，以实现成本效益，小型化，相位工程设备，这些设备对偏振不敏感，在大范围入射角范围内工作，并结合高效聚焦和光栅响应，除了光谱学之外，还可以应用于多光谱光学检测，量子信息源和片上传感。该项目为下一代用于光学成像、传感和光谱学的超紧凑光谱调相设备奠定了基础，从而产生了广泛的影响。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。

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.