Collaborative Research: Non-Hermitian wave mixing for highly efficient nonlinear light sources

第一部分：对复杂光子系统和平台不断增长的需求继续推动探索新的光学几何形状，概念和材料系统，以实现复杂和前所未有的功能。另一方面，这些需要对光与物质的相互作用有更深入的理解和精确的控制。现代技术在计算、通信、传感和探测以及生物成像等方面的应用具有极大兴趣的一项特别研究活动是开发有效的相干光源，这种光源能够提供比传统激光器所获得的波长更长的发射。非线性的波混合过程，通过不同颜色的光可以混合产生新的颜色，是经常追求的策略。这些非线性光源的实现需要严格的物理条件，由光子动量守恒决定。这对设计造成了严重的限制，并且迄今为止阻碍了许多高度非线性材料（如半导体）作为非线性光源的利用。本项目将从理论上和实验上探索克服这些困难的新策略，通过设计光子结构中的光损失来控制非线性波混频过程，从输入光子（泵浦光子）到具有所需波长（颜色）的信号光子产生不可逆的能量转换。这将使新的芯片级光源在医疗保健、信息技术和传感领域的实际应用成为可能。协同作用下，该项目还包括旨在增加光子领域未来科学家和工程师多样性和人才库的外展活动。该团队将为研究生、本科生和高中生组织参与性活动、实验室开放日和研究培训机会，重点关注来自代表性不足群体的学生。第二部分：该研究将建立一个综合的理论和实验平台，通过光谱和空间工程的光损失在波混频过程中开发高效的非线性光源。损耗工程通过去除过程中产生的空闲组件来实现非厄米相位匹配，从而允许使用高度非线性的材料，这些材料不容易进行厄米相位匹配。这也允许在这种材料中发生非线性过程，而无需严格的波导，色散工程或准相位匹配标准。实现这一目标的途径是：1)建立理论模型和平台，研究损失工程对非线性混频过程动力学和效率的影响；2)研究设计策略和实验技术，以可控地引入非对称的波混频损耗和增益曲线；3)通过损耗工程演示波导和谐振器中的光学参数放大和高效非线性光源。非厄米结构及其对光学过程的影响，如果得到正确的理解和控制，将为探索新型光子器件和光源提供一个令人兴奋的机会。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。

Part 1: The growing demand for complex photonic systems and platforms continues to push for exploring new optical geometries, concepts and material systems to achieve sophisticated and unprecedented functionalities. These, on the other hand, require a deeper understanding and precise control of the interaction of light with material. One particular research activity of great interest to modern technology, enabling applications in computing, communication, sensing and detection, and bio-imaging, is the development of efficient coherent light sources that can provide emission at wavelengths beyond those obtained by conventional lasers. Nonlinear wave-mixing processes, by which light of different colors can intermix to produce new colors, are often the strategy pursued. The implementation of these nonlinear light sources requires stringent physical conditions dictated by the conservation of photon momentum. This poses serious limitations on the design and, to date, impede the utilization of many highly nonlinear materials such as semiconductors as nonlinear light sources. This project will explore theoretically and experimentally novel strategies to overcome these difficulties by engineering the optical losses in the photonic structures to control the nonlinear wave-mixing process, creating irreversible energy conversion from input photons (pump photons) to signal photons with the desired wavelength (color). This will enable the practical implementation of new chip-scale light sources toward applications in healthcare, information technology and sensing. Synergistically, this project includes outreach activities aiming at increasing the diversity and talent pool of future scientists and engineers in photonics. The team will organize participatory activities, lab open houses, and research training opportunities for graduate, undergraduate, and high school students, with a focus on students from underrepresented groups. Part 2: The proposed research will develop an integrated theoretical and experimental platform for developing efficient nonlinear light sources via spectral and spatial engineering of optical losses in wave-mixing processes. Loss engineering enables non-Hermitian phase matching by removing the idler component produced in the process, and thus allowing the use of highly nonlinear materials that do not lend themselves easily to Hermitian phase-matching. This also allows the nonlinear process to take place in such materials without stringent waveguiding, dispersion engineering or quasi-phase matching criteria. The approaches in pursuit of this goal are: 1) Developing a theoretical model and platform to study the impact of loss engineering on the dynamics and efficiency of nonlinear wave-mixing process; 2) Investigating design strategies and experimental techniques to controllably introduce asymmetric loss and gain profiles for wave-mixing; and 3) Demonstrate optical parametric amplification and efficient nonlinear light sources in waveguides and resonators by loss engineering. The structure of non-Hermiticity and its effects on optical processes, if properly understood and controlled, will present an exciting opportunity to explore novel photonic devices and light sources.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.