RII Track-4: NSF: Development of Semiconductor Lasers and Passive Devices on a Single Sapphire Platform for Integrated Microwave Photonics

该项目的目标是开发一种新的集成微波光子学（IMWP）技术的蓝宝石平台，将无线信号处理和传输的挑战从电子领域转移到光子领域，为实现更高的数据通信速率提供丰富的新机会。蓝宝石平台的特点：(1)热膨胀系数紧密匹配，更有利于集成优秀的激光材料；(2)采用氮化硅技术实现超低损耗波导。NSF EPSCoR RII Track-4项目为阿肯色大学的一名副教授和一名研究生提供奖学金，以访问位于阿灵顿的德克萨斯大学，旨在建立强有力的研究合作，以支持推进蓝宝石基IMWP技术的长期研究目标。这项工作为研究在单一蓝宝石平台上获得一套高性能光学元件的可行性奠定了基础。如果成功，新的蓝宝石平台将在国防系统中有巨大的应用，如雷达信号处理，以及许多民用应用，如5G系统、蜂窝和医疗成像系统。除了研究生和本科生的参与外，主要研究者还从当地的HBCU招募学生。该项目的愿景是利用一种新的材料系统，在单个芯片上实现微波光子学的有源和无源光电子元件的异构集成。其动机在于蓝宝石为一个完全集成的解决方案的可行性，包括光源、调制器、光检测、波导、耦合器、谐振器、CMOS控制电路、蓝宝石上硅（SOS）电路等全套组件的一体化蓝宝石平台，实现高性能、低成本的混合信号光链路。该蓝宝石平台采用成熟的SOS CMOS和RF高频电路技术，具有低功耗的特点。蓝宝石平台具有(1)不能传导电流从而减少寄生；(2)有足够的折射率对比度，光功率损耗低；(3)具有非常独特的热膨胀系数，可与许多III-V级材料相匹配，具有高运行可靠性。研究目标集中在蓝宝石激光器和无源器件构建模块的开发上，包括波导（直波导和弯波导）、分路器、耦合器和环形谐振器。研究目标是：(1)通过晶片间共价键合技术的发展，在蓝宝石衬底上获得高性能III-V激光器；(2)利用新设计的蓝宝石上氮化硅技术开发低损耗波导；(3)对谐振器、耦合器等进行研制，得到一套无源器件。这种基于蓝宝石的技术有望在铸造厂制造时以非常低的成本减少尺寸、重量和功耗（SWaP）。这有可能使雷达信号处理、5G系统、卫星通信和医疗成像系统中的许多应用受益。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。

The goal of this project is to develop a new sapphire platform for integrated microwave photonics (IMWP) technology, which transfers wireless signal processing and transmission challenges from the electronic to the photonic domain, could provide a wealth of new opportunities to achieve higher data communication rate. Sapphire platform features: (1) more favorable for the integration of excellent laser materials due to a closely matched coefficient of thermal expansion, and (2) attainable ultra-low-loss waveguides using silicon nitride technology. This NSF EPSCoR RII Track-4 project provides a fellowship to an Associate Professor and a graduate student at the University of Arkansas to visit the University of Texas at Arlington, aiming to establish a strong research collaboration that would support the long-term research goal to advance sapphire based IMWP technology. This work lays the foundation to investigate the feasibility of obtaining a complete set of high-performance optical components heterogeneously integrated on a single sapphire platform. If successful, the new sapphire platform would have tremendous applications in defense systems, such as Radar signal processing, and numerous civilian applications, such as 5G system, cellular, and medical imaging systems. In addition to the involvement of graduate and undergraduate students, the principal investigator recruits students from a local HBCU. The vision of this project is to leverage a new material system to enable heterogeneous integration of active and passive optoelectronics components, for microwave photonics, on a single chip. The motivation lies in the feasibility of sapphire for a fully integrated solution to include a complete set of components with light source, modulator, light detection, waveguides, couplers, resonators, CMOS control circuit, Silicon on Sapphire (SOS) circuit all-in-one sapphire platform to achieve high-performance low-cost mixed-signal optical links. The proposed sapphire platform utilizes the mature SOS CMOS and RF high frequency circuit technology featuring low power consumption. The sapphire platform has the (1) inability to conduct current thereby reducing parasitics; (2) sufficient optical index contrast resulting in low optical power loss; and (3) very uniquely, an excellent thermal expansion coefficient match to many III-V materials for high operating reliability. The research goal focuses on the development of sapphire based lasers and passive device building blocks including waveguides (straight and bend), splitters, couplers, and ring resonators. The research objectives are: (1) obtain the high performance III-V lasers on sapphire substrate via the development of wafer-to-wafer covalent bonding technology; (2) develop the low loss waveguide using the newly designed silicon nitride on sapphire technology; and (3) develop the resonators, couplers, etc. to obtain a set of passive devices. The proposed sapphire-based technology offers the promise of reduced size weight and power (SWaP) at a very low cost when manufactured in a foundry. This has the potential to benefit many applications in Radar signal processing, 5G system, satellite communications, and medical imaging systems.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.