Collaborative Research: Thin-Film Chalcogenide Glass Materials for High-Quality Integrated Photonics

非技术描述：麻省理工学院和华盛顿大学之间的这项合作研究项目的主要目标是：(1)通过光谱研究对薄膜硫系玻璃材料的光损耗机制进行批判性理解，(2)利用创新的加工科学来合成薄膜形式的超低损耗硫系玻璃材料，(3)制造具有新功能的光学器件。基于这些基本发现，本研究旨在展示具有高质量因数的硫系玻璃谐振腔器件，作为光子传感器、光发射器和非线性光信号处理系统的基石。该研究有望在材料科学、纳米技术、非线性光学和集成光子学等领域产生重大影响。参与的本科生和研究生研究人员受益于麻省理工学院和华盛顿大学两个研究小组之间的跨学科合作。从研究中获得的结果被纳入麻省理工学院玻璃材料的新本科课程。该项目还通过实验室开放日和暑期实习项目在两个校区扩展了K-12计划。技术描述：硫系玻璃（ChGs）被公认为集成光子学的新兴材料平台，因为它具有独特的性能，如基片盲集成能力、极端的加工多功能性、通过成分合金化广泛可调的光学和热特性、大克尔非线性和宽带光学透明度。与二氧化硅玻璃不同，多组分硫系玻璃包含更多样化的纳米级玻璃网络部分。这些特性导致复杂的结构转换和光损失，对加工历史高度敏感，不能用经典的瑞利散射形式来描述。因此，如果不深入了解硫族化合物薄膜的微观结构演变动力学和损失机制，传统的降低损耗方法就不能简单地转移到硫族化合物材料上。由于薄膜中相互作用体积小，使得区分硫系化合物薄膜中的光学损耗贡献的挑战进一步复杂化，这严重限制了大多数传统光学表征方法的灵敏度。在这个项目中，我们开发了新的基于波导和谐振器的光谱表征方法来提取关键的材料信息，如纳米级相组成、本征吸收和不同的散射过程。该项目促进了我们对材料光学特性相关的纳米级结构转化机制以及ChG材料中结构-加工-性能关系的理解。通过将新型表面张力辅助加工技术的动力学建模和实验验证相结合，该项目还旨在开发性能超过当前最先进水平的超高质量平面ChG结构。

Nontechnical Description: The main objectives of this collaborative research project between MIT and Washington University are (1) to develop critical understandings of the optical loss mechanisms in thin-film chalcogenide glass materials through spectroscopic studies, (2) to exploit innovative processing science to synthesize ultra-low-loss chalcogenide glass materials in the thin-film form and (3) to fabricate optical devices with novel functionalities. Based on these fundamental findings, the research aims to demonstrate chalcogenide glass resonant cavity devices with high quality factors as building blocks for photonic sensors, light emitters and nonlinear optical signal processing systems. The research is expected to have significant impacts on many areas including materials science, nanotechnology, nonlinear optics and integrated photonics. The participating undergraduate and graduate researchers benefit from the cross-disciplinary collaboration between the two research groups at MIT and Washington University. Results obtained from the research are incorporated into new undergraduate courses on glass materials at MIT. The project also expands K-12 initiatives on both campuses through lab open houses and summer internship programs.Technical Description: Chalcogenide glasses (ChGs) are recognized as an emerging material platform for integrated photonics given their unique properties, such as substrate-blind integration capacity, extreme processing versatility, widely tunable optical and thermal characteristics via composition alloying, large Kerr nonlinearity, and broadband optical transparency. Unlike silica glass, multi-component chalcogenide glasses contain a far more diverse group of nanoscale glass network moieties. These properties result in complicated structural transformations and optical losses that are highly sensitive to processing history and cannot be described using the classical Rayleigh scattering formalism. As a consequence, traditional loss reduction methods cannot be simply transferred to chalcogenide materials without an in-depth understanding of the kinetics of micro-structural evolution and loss mechanisms in chalcogenide films. The challenge of differentiating optical loss contributions in chalcogenide films is further compounded by the small interaction volume in thin films, which severely limits the sensitivity of most traditional optical characterization methods. In this project, new waveguide- and resonator-based spectroscopic characterization methods are developed to extract critical material information such as nanoscale phase composition, intrinsic absorption, and different scattering processes. The project advances our understanding of the nanoscale structural transformation mechanisms associated with material's optical characteristics as well as the structure-processing-property relationship in ChG materials. By combining kinetic modeling and experimental validation of novel surface-tension-assisted processing techniques, the project also aims to develop ultra-high-quality planar ChG structures with performance exceeding the current state-of-the-art.