Collaborative Research: Nanopatterning and temporal control of phase-change materials for reconfigurable photonics

动态控制光的能力，通常被称为可重构光子学，在日常生活中随处可见，从超市条形码阅读器到深空望远镜的自适应光学，从动态剧院照明到医学显微镜，都有各种各样的应用。目前，这些应用依赖于空间光调制器(SLM)技术，但这些技术有很大的局限性：它们速度慢、成本高、涉及脆弱的运动部件，而且通用性不足以适应现代挑战。在这个项目中，一种被称为相变材料(PCM)的材料被用来制造一种速度更快、成本更低的空间光调制器。这是通过将蓝光光盘中常用的一种PCM(称为GST)与新型纳米制造和电子控制相结合来实现的，以创建性能指标远远超过当前可用的先进的可重新配置的光子设备。这个项目的好处有三个方面。这个项目的核心是两个研究领域的交集：纳米尺度的热学和光子学。这将导致这两个领域在一个新的和未探索的维度上的进步。在教育方面，该项目将首次允许代顿大学和斯坦福大学之间的学生交流。它还将加强与少数族裔服务机构的关系。这项工作的长期影响将是为提供紧凑、高速、低功耗的设备提供一个垫脚石，这些设备使用廉价的制造方法制造，用于基于可重构光子学的技术。用于可重构光子应用的光调制的当前技术水平依赖于通过硅上液晶(LCoS)或微电子机械(MEMS)系统的空间光相位调制，这两种系统都具有重大限制。目前的一个障碍是这些器件的运行速度，另一个障碍是它们的制造工艺的复杂性和低成品率。这项研究的目标是利用相变材料(PCM)以无损、高速的方式对光进行相干的空间和时间控制，远远超过今天标准的液晶和MEMS器件的性能。相变材料通过受控的晶态到非晶态的相变改变其光学性质(折射率)，使其成为光调制应用的理想选择。然而，PCM仍然存在两个问题：a)相变缓慢，b)相变是二进制的(开/关)，阻碍了必要的相位调制设备的实施。这一建议着眼于这两个问题，并提出了一种基于纳米颗粒和相变过程的时间控制的新颖而统一的解决方案。通过使用一种新的可伸缩的自组装图案化技术，我们改变了温度动力学，并将相变速度提高了数量级。通过使用时间控制的电刺激，有可能实现真正的光的连续相位调制，克服材料本身的二元性质。相变材料自然适合大规模制造，如果它们的全部潜力被开发出来，就有可能改变可重新配置的光子学和光调制器件的领域。该项目旨在通过在通常看不到太多重叠的工程领域之间进行新的合作来实现这一潜力。最终，目标是实现基本的空间光调制设备，具有独特的工程热性能，这将为这些领域提供一种新的交叉授粉，这可能会导致这两个科学领域的进一步发展。

The ability to control light dynamically, commonly known as reconfigurable photonics, is ubiquitous in everyday life with diverse and varied applications ranging from supermarket barcode readers to adaptive optics for deep-space telescopes, and from dynamic theatre lighting to medical microscopy. Currently, these applications rely on spatial light modulator (SLM) technologies that have significant limits: They are slow, costly, involve fragile moving parts, and not versatile enough to adapt to modern challenges. In this project, a material known as phase-change materials (PCMs) is used to create a faster and less costly spatial light modulator. This is done by combining a type of PCM that is commonly used in Blu-Ray discs, known as GST, with new types of nanofabrication and electronic control to create advanced reconfigurable photonic devices with performance metrics that far exceed what is currently available. The benefits of this project are three fold. At the core, this project falls at the intersection between two fields of research: nanoscale thermal science, and photonics. This will lead to an advancement of both fields in a new and unexplored dimension. On the education front, the project will allow for student exchanges between the University of Dayton and Stanford University, for the first time. It will also bolster the relationship with minority-serving institutes. The longer term impact of this work will be to provide a stepping stone towards providing compact, high speed, low power consumption devices, manufactured using inexpensive fabrication methods for use in technologies based on reconfigurable photonics. Current state-of-the art in light modulation for reconfigurable photonic applications relies on spatial light phase modulation via liquid-crystal on silicon (LCoS) or Microelectromechanical (MEMS) systems, both of which have major limitations. One current hurdle is the speed at which these devices operates, and the other is the complexity and low-yield of their fabrication process. The goal of this research is to use phase-change materials (PCMs) for coherent spatial and temporal control of light in a lossless, high-speed manner, well beyond the performance of standard liquid crystal and MEMs devices today. PCMs alter their optical properties (refractive index) through a controlled crystalline-to-amorphous phase transition, making them ideal for light modulation applications. However, two problems persist with PCMs: a) The phase transition is slow and b) the phase transition is binary (on/off), preventing the implementation of the necessary phase modulation devices. This proposal looks at both these problems and presents a novel and unified solution based on nanopatterning and temporal control of the phase-change process. Through the use of a new and scalable technique for self-assembled patterning, we alter the temperature dynamics and increase the speed of the phase-change by orders of magnitude. By using temporally-controlled electric stimulus, it is possible to achieve true continuous phase modulation of light overcoming the binary nature of the material itself. Phase-change materials, which naturally lend themselves to mass manufacturing, have the potential to alter the area of reconfigurable photonics and light modulation devices provided their full potential is exploited. This project aims to achieve that potential through a new collaboration between fields of engineering that typically do not see much overlap. Ultimately, the goal is to implement basic spatial light modulation devices, with unique engineered thermal properties, which presents a new cross-pollination of these fields, which could lead to further developments in both areas of science.