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.

题目：“硅中硅”波导的全光制造本项目的目标是开发一种直接激光写入方法，以低传播损耗的方式生产嵌入硅中的三维（3D）光波导。虽然在玻璃内部已经证明了低损耗的3D波导，但到目前为止，在硅内部写入波导的典型损耗要高出一个数量级以上。研究小组面临的两个主要挑战是能量沉积不足和硅内部的随机物质变化，这是通过新的光束传输和对强激光照射下材料响应的基本理解来解决的。本项目开发的直接激光写入方法简化了硅光子器件的制造过程，增加了通信带宽，促进了器件的小型化，并显著提高了片上和片对片的数据处理能力。该方法能够与选择性湿法蚀刻相结合来制造微流体通道，从而实现光子、电子和流体功能在单个芯片中的集成。该团队与当地和国家光电子产业的紧密联系，通过加快拟议技术从实验室到工厂的过渡，增强了项目的社会影响。通过本科生和研究生培训、课堂教学模块和面向未来劳动力发展的K-12外展活动，研究与教育紧密结合。该基金支持在受限环境下激光诱导相变的基础研究，其目标是创建低损耗、高折射率对比度、深硅三维波导（“Si-in-Si”）。目前的Si-in-Si波导损耗大，折射率对比度低，不适合用于大多数光子学应用。性能差的原因是由于激光聚焦区域的局部温度驱动下的微纳米尺度的不均匀性，包括混合硅相。在这个项目中，飞秒-纳秒激光脉冲将用于实现过渡到非晶和高压相所需的能量密度。将进行建模、模拟和实验，以确定导致热力学稳定的Si相的转变途径。将制作一个三维分路器作为测试结构，对其光学性能进行测量，并进行理论和仿真比较。本项目将促进对(1)具有高非线性和强双光子吸收特性的超短激光脉冲在硅中的时空约束的认识；(2)压力诱导的Si相变，特别是向不常见的高压相转变；(3)三维结构波导的弯曲半径、模式质量等光学性能。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。