Ferromagnetic Magnetooptical Oxides for Nonreciprocal Photonic Devices

非技术描述基于光流的光学计算机芯片比依靠电流的传统计算机芯片工作速度更快，耗电量更少。光学计算机芯片需要各种组件，包括片上激光器、波导、调制器和隔离器。隔离器充当光的二极管，让光在一个方向上流动，但阻止它在另一个方向流动，是光学电路的重要组成部分。隔离器是由透明的磁性材料制成的，但是由磁性石榴石组成的传统材料已被证明很难在制造计算机芯片的普通半导体衬底上生长。因此，我们非常需要开发新的磁性材料，这种材料可以方便地生长在硅等衬底上，因为这将使功能齐全的光学器件得以制造出来，最终目标是改变光学计算领域，实现更快、更低功耗的计算机。本项目研究新型磁性氧化物材料，了解材料的组成、结构、应变状态与其磁性和光学性能之间的关系，并基于这些材料设计新型隔离器。这项工作的更广泛影响包括培训学生，通过麻省理工学院开放课程计划向公众推广，指导高中教师，以及与学校的互动。具有磁光活性的磁性氧化物是光学隔离器等光子器件的重要组成部分。隔离器就像光学二极管一样，保护激光不受反向反射光的影响，因此在光子器件中至关重要。将光电路的所有元件集成到光电子芯片上，可以实现光计算，具有速度快、功耗低的优点。然而，传统的磁光材料石榴石很难集成到Si或III-V平台上。因此，人们对开发具有良好的光学透明度和高法拉第旋转的替代材料非常感兴趣，这些材料也可以集成到光子衬底上。本项目主要开发基于钙钛矿的薄膜磁光材料，并通过在A和B位点上取代离子和在氧位点上存在空位，以及通过控制应变和磁弹性各向异性来控制磁性和光学性能。此外，基于光通过薄膜时所经历的非互易相移，设计了磁光隔离器并建立了模型。这项工作的更广泛影响包括开发一种光学隔离器，如果成功，可能会改变集成光学领域；学生的培养；并通过麻省理工学院开放课程计划向公众推广，为高中教师提供指导，并与学校互动。

NON-TECHNICAL DESCRIPTIONOptical computer chips, which are based on the flow of light, could work faster and use less power than conventional computer chips, which rely on the flow of electrical currents. Optical computer chips require various components including on-chip lasers, waveguides, modulators, and isolators. Isolators act as diodes for light, letting it flow in one direction but blocking its flow in the other direction, and are essential components of an optical circuit. Isolators are made from transparent magnetic materials, but the traditional materials, which consist of magnetic garnets, have proven to be very difficult to grow on common semiconductor substrates from which computer chips are made. There is therefore a great need to develop new magnetic materials which can be conveniently grown on substrates such as silicon because this will enable fully functional optical devices to be made, with the ultimate goal of transforming the field of optical computing and enabling faster, lower-power computers. This project studies new magnetic oxide materials, understanding the relation between the composition, structure, strain state of the materials and their magnetic and optical properties, and prototyping new isolator designs based on these materials. The broader impacts of the work include the training of students, and outreach to the public through the MIT OpenCourseWare initiative, mentoring of high school teachers, and interactions with schools. TECHNICAL DETAILSMagnetic oxides which are magnetooptically active are an essential component of photonic devices such as optical isolators. Isolators act as optical diodes, protecting lasers from back-reflected light, and are therefore of critical importance in photonic devices. Integrating all the components of an optical circuit onto an optoelectronic chip would enable optical computation to be carried out, with its advantages of high speed and low power consumption. However, the traditional magnetooptical material, garnet, has proved difficult to integrate onto a Si or III-V platform. Therefore, there is considerable interest in developing alternative materials which have good optical transparency and high Faraday rotation, and can also be integrated onto photonic substrates. This project develops thin film magnetooptical materials based primarily on perovskites, and controls the magnetic and optical properties by the substitution of ions onto the A and B sites and the presence of vacancies on the oxygen sites, and by controlling the strain and the magnetoelastic anisotropy. In addition, magnetooptical isolators are designed and modeled based on the nonreciprocal phase shift experienced by light passing through the films. The broader impacts of the work include the development of an optical isolator that, if successful, could transform the field of integrated optics; the training of students; and outreach to the public through the MIT OpenCourseWare initiative, mentoring of high school teachers, and interactions with schools.