MRI: Development of Ultrafast Near-Field Scanning Optical Microscope

自然和工程系统中的许多现象既是空间的，也是时间的，这意味着它们涉及到非均匀模式的动态变化和运动。例如波的传播、加热和冷却、化学反应和扩散。将这些现象可视化的能力从根本上受到它们的速度和体积的限制。科学在显微镜的空间分辨率方面取得了显著的进步，这使得现在已经成熟的纳米技术领域成为可能。与此同时，脉冲激光系统可以以飞秒的分辨率解析动态过程--甚至比最好的电子探测器或相机都要快得多。该项目旨在开发一种新型仪器，将近场显微镜的空间能力与飞秒激光的时间分辨率相结合，这是目前商业仪器所不具备的。该工具将能够分辨纳米尺度的空间结构，同时测量从纳米电子器件到金属纳米结构和太阳能电池等系统中的飞秒分辨率的超快效应。这一独特的仪器将为各级科学家和学生提供宝贵的培训，他们将开发和利用它。飞秒激光和近场显微镜这两种不同技术的结合，将需要在该项目的三年期间进行大量的工程研究、迭代、优化和系统集成。该仪器将用超快可调谐脉冲激光取代近场扫描光学显微镜中通常使用的连续波激光，以产生强烈的空间和时间局域光刺激，可以在纳米尺度上激发材料或器件的非线性效应。然后将使用第二个较弱的时间延迟光脉冲来探测飞秒分辨率的特性和动力学。拟议的系统将允许在340纳米到12,000纳米的波长范围内进行时间分辨率和空间分辨率的测量。该新仪器将能够研究金属和二维(2D)材料中的热载流子动力学，研究用于先进光电子学的钙钛矿材料的动态电响应，直接成像纳米光电子器件和共振结构，并观察过渡金属氧化物中的不同表面化学和晶界。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Many phenomena in natural and engineered systems are both spatial and temporal, meaning that they involve dynamical changes and movements of nonuniform patterns. Examples include wave propagation, heating and cooling, chemical reactions, and diffusion. The ability to visualize these phenomena is fundamentally limited both by how fast they are and how small they are. Science has made remarkable improvements in the spatial resolution of microscopes, which has enabled the now-mature field of nanotechnology. At the same time, pulsed laser systems can resolve dynamical processes with femtosecond resolution -- far faster than even the best electrical detectors or cameras. This project aims to develop a novel instrument that will combine the spatial capabilities of a near-field microscope with the temporal resolution of a femtosecond laser, which is currently not available in commercial instruments. This tool will be capable of resolving nanoscale spatial structure, while simultaneously measuring ultrafast effects with femtosecond resolution in systems ranging from nanoelectronic devices to metallic nanostructures and solar cells. The unique instrument will provide valuable training for scientists and students at all levels, who will both develop and utilize it.The combination of two different technologies, the femtosecond laser and the near-field microscope, will require significant engineering research, iteration, optimization, and system integration over the three-year period of this project. The proposed instrument will replace the continuous-wave laser typically used in a near-field scanning optical microscope with an ultrafast tunable pulsed laser, in order to produce an intense spatially and temporally localized optical stimulus that can excite nonlinear effects in the material or device at the nanoscale. A second, weaker temporally-delayed optical pulse will then be used to probe the properties and dynamics with femtosecond resolution. The proposed system will allow for time-resolved and spatially-resolved measurements at wavelengths ranging from 340 nm to 12,000 nm. The new instrument will enable the study of hot-carrier dynamics in metals and two-dimensional (2D) materials, investigation of the dynamic electrical response of perovskite materials for advanced optoelectronics, direct imaging of nanophotonic devices and resonant structures, and observation of heterogeneous surface chemistry and grain boundaries in transition-metal oxides.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.