Collaborative Research: All-Optical Fabrication of Low-Loss, High-Index-Contrast, Silicon-in-Silicon Waveguides

合作研究：低损耗、高折射率对比度、硅中硅波导的全光学制造

• 批准号: 2128962
• 负责人: Shuting Lei
• 金额: $ 16.15万
• 依托单位: Kansas State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-15 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128962&HistoricalAwards=false
• 关键词: Collaborative; Research; Optical; Fabrication; Low

Title: All-optical fabrication of “silicon-in-silicon” waveguidesThe goal of this project is to develop a direct laser writing method to produce three-dimensional (3D) optical waveguides embedded inside silicon with low propagation loss. Although low-loss 3D waveguides have been demonstrated inside glass, the typical loss for waveguides written inside silicon so far is more than one order of magnitude higher. Two main challenges faced by the research team are insufficient energy deposition and random material change inside silicon, which are tackled through novel beam delivery and fundamental understanding of material response under intense laser irradiation. The direct laser writing method developed in this project simplifies fabrication procedures for silicon photonic devices, increases communication bandwidth, facilitates device miniaturization, and significantly enhances on-chip and chip-to-chip data processing capabilities. This method has the capability to be integrated with selective wet etching to fabricate microfluidic channels, enabling the integration of photonic, electronic and fluidic functionalities in a single chip. The team’s strong connection with local and national photonics industries enhances the societal impact of the project by expediting lab-to-fab transition with the proposed technology. The research is tightly integrated with education through undergraduate and graduate student training, classroom teaching modules, and K-12 outreach events for future workforce development. This grant supports basic research on laser-induced phase transformation in confined environment, with the goal to create low-loss, high-index-contrast, three-dimensional (3D) waveguides deep inside silicon (“Si-in-Si”). Current Si-in-Si waveguides have large loss and low contrast of refractive indices, making them unsuitable to be used in most photonics applications. The poor performance is due to micro- and nano-scale inhomogeneities consisting of mixed Si phases driven by local temperature in the laser focal region. In this project, femtosecond-nanosecond laser pulses will be used to achieve energy density required for the transition to amorphous and high-pressure phases. Modelling, simulation and experiments will be conducted to identify transition pathways leading to thermodynamically stable Si phases. A 3D splitter will be fabricated as a testing structure and its optical performance will be measured and compared with theory and simulation. This project will advance the understanding of (1) space-time confinement of ultrashort laser pulses in Si which exhibits high nonlinearity and strong two-photon absorption; (2) pressure-induced phase transition of Si, especially toward uncommon high-pressure phases; and (3) optical performance of waveguides with 3D architecture, such as bending radius and mode quality.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.

本项目的目标是开发一种直接激光写入的方法，以制造嵌入在硅中的低传输损耗的三维(3D)光波导。虽然已经在玻璃中展示了低损耗的3D波导，但到目前为止，写入硅中的波导的典型损耗要高出一个数量级以上。研究团队面临的两个主要挑战是能量沉积不足和硅内部材料的随机变化，这些挑战可以通过新颖的光束传输和对材料在强激光照射下的响应的基本了解来解决。该项目开发的激光直接写入方法简化了硅光子器件的制造程序，增加了通信带宽，促进了器件小型化，并显著增强了片上和芯片间的数据处理能力。该方法能够与选择性湿法刻蚀集成以制造微流控通道，从而能够在单个芯片中集成光子、电子和流体功能。该团队与当地和全国光电子行业的紧密联系，通过加快拟议技术从实验室到工厂的过渡，增强了该项目的社会影响。这项研究通过本科生和研究生培训、课堂教学模块以及为未来劳动力发展举办的K-12外展活动，与教育紧密结合。这笔赠款支持在受限环境中进行激光诱导相变的基础研究，目标是制造低损耗、高折射率对比度的三维(3D)波导，深入硅(“Si-in-Si”)。目前的Si-In-Si光波导具有损耗大、折射率对比度低等缺点，不适合在大多数光子学应用中使用。性能较差的原因是激光焦区的局部温度驱动了由混合硅相组成的微纳尺度的不均匀。在这个项目中，将使用飞秒-纳秒激光脉冲来实现向非晶相和高压相转变所需的能量密度。将进行建模、模拟和实验，以确定导致热力学稳定的硅相的转变路径。制作了一个三维分束器作为测试结构，对其光学性能进行了测试，并与理论和模拟进行了比较。该项目将促进人们对(1)超短激光脉冲在硅中表现出的高度非线性和强双光子吸收的时空限制；(2)硅的压力诱导相变，特别是向不常见的高压相的转变；以及(3)3D结构光波导的光学性能，如弯曲半径和模式质量。这一奖项反映了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。