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，在日常生活中无处不在，有各种各样的应用，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。目前，这些应用依赖于空间光调制器（SLM）技术，这些技术有很大的局限性：它们速度慢，成本高，涉及易碎的运动部件，并且不够通用，无法适应现代挑战。在这个项目中，一种被称为相变材料（PCMs）的材料被用来制造一个更快、更便宜的空间光调制器。这是通过将蓝光光盘中常用的一种称为GST的PCM与新型纳米制造和电子控制相结合来实现的，以创建先进的可重构光子器件，其性能指标远远超过目前可用的。这个项目的好处是三重的。这个项目的核心是两个研究领域的交叉：纳米尺度的热科学和光子学。这将导致这两个领域在一个新的和未开发的维度上的进步。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换。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。目前，用于可重构光子应用的光调制技术依赖于通过液晶硅（LCoS）或微机电（MEMS）系统进行空间光相位调制，这两种系统都有很大的局限性。目前的一个障碍是这些设备的运行速度，另一个是它们的制造过程的复杂性和低产量。本研究的目标是使用相变材料（PCMs）以无损，高速的方式进行光的相干空间和时间控制，远远超出当今标准液晶和MEMs器件的性能。PCMs通过控制晶体到非晶态的相变改变其光学特性（折射率），使其成为光调制应用的理想选择。然而，pcm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器件的实现。本提案着眼于这两个问题，并提出了一种基于纳米图案和相变过程的时间控制的新颖统一的解决方案。通过使用一种新的可扩展的自组装模式技术，我们改变了温度动态，并将相变的速度提高了几个数量级。通过使用暂时控制的电刺激，可以克服材料本身的二元性，实现光的真正连续相位调制。相变材料天生适合大规模生产，如果充分利用其潜力，就有可能改变可重构光子学和光调制器件的领域。该项目旨在通过工程领域之间的新合作来实现这一潜力，而这些领域通常看不到太多重叠。最终，我们的目标是实现具有独特工程热性能的基本空间光调制装置，这为这些领域提供了一个新的交叉授粉，这可能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.