Compressive ultrahigh-speed imaging beyond trillions of frames per second using spatiotemporally encoded metasurfaces

捕捉超快现象的实际发生时间在发现新的科学原理和开发新技术方面发挥着核心作用。例如，使用泵浦-探测光谱监测瞬时分子状态的能力为化学反应提供了新的见解。典型的泵浦-探测方法的前提是相同的泵浦脉冲会引起相同的现象，从而提供了重复研究它的机会。然而，许多超快现象要么是不可重复的，要么是不可逆的，因此不能使用传统的泵浦-探测技术来成像。超过每秒万亿帧的紧凑、经济实惠和单次拍摄的超快成像技术在观察非周期和不可逆转的瞬时事件方面仍然是一个未得到满足的需求。这项研究融合了一种名为超表面的人工工程合成表面和压缩传感技术，旨在开发一种紧凑、超表面功能的单次拍摄成像系统，用于捕捉超快现象的动态特性，并揭示支配这种动力学的未知或隐藏的规律。该计划将把不同的研究、教学和推广活动紧密结合在一起，以加强大学的光子学教育基础设施，并将形成一个独特的平台，将对人力资源和教育产生广泛影响。拟议的研究还将在学院和K-12阶段创造机会，相关成果将用于为当地教育活动设计展览。这项研究计划的总体目标是将两种尖端技术--光学超表面和压缩传感--整合在一起，开发一种紧凑、经济高效的单次成像系统，实现每秒数万亿帧以上的超高速成像。该系统可以用来捕捉超快现象的动力学特性，并揭示支配这种动力学的未知或隐藏的规律。在亚表面--一种由亚波长大小的元素(元原子)组成的合成表面，在纳米尺度上进行局部电磁响应--的支持下，超快成像系统在空间和时间上都使用了亚表面“像素化”编码器对输入的光学信息进行编码。编码后的信息随后被普通摄像机捕获。通过利用压缩传感算法和MetasSurface编码器的高时间分辨率，通过计算重建了一部揭示(x，y，z，t)维信息的三维超快电影，以计算重建以前无法实现的超快非周期事件。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。

Capturing ultrafast phenomena in their actual time of occurrence plays a central role in the discovery of new scientific principles and the development of new technologies. For example, the abilities to monitor transient molecular states using the pump-probe spectroscopy have provided new insight into chemical reactions. The premise for a typical pump-probe method is that identical phenomenon will be induced by identical pump pulses, affording the opportunity to study it repeatedly. However, many ultrafast phenomena are either non-repeatable or irreversible, and thus they cannot be imaged using the conventional pump-probe techniques. Compact, affordable, and single-shot ultrafast imaging technology beyond trillions of frames per second remains an unmet need for the observation of non-periodic and irreversible transient events. Merging an artificially engineered synthetic surface, called metasurface, and the compressive sensing technology, the research aims to develop a compact, metasurface-enabled, single-shot imaging system for capturing the dynamic properties of ultrafast phenomena and uncovering the unknown or hidden laws that govern such dynamics. The program will closely integrate diverse research, teaching, and outreach activities together to enhance photonics education infrastructures at the university and will form a unique platform that will make broad impacts on human resource and education. The proposed research will also generate opportunities at both the college and K-12 levels and the related results will be used for designing exhibitions for local educational events. The overarching goal of this research program is to integrate two cutting-edge technologies – the optical metasurface and compressive sensing – together to develop a compact, cost-effective, single-shot imaging system enabling ultrahigh-speed imaging beyond trillions of frames per second. The system can be used for capturing the dynamic properties of ultrafast phenomena and uncovering the unknown or hidden laws that govern such dynamics. Empowered by the metasurface – a synthetic surface consisting of subwavelength-sized elements (meta-atoms) that locally engineer the electromagnetic response on the nanoscale – the ultrafast imaging system encodes the incoming optical information using a metasurface-enabled “pixelized” encoder both in space and in time. The encoded information is then captured by a normal camera. By leveraging the compressive sensing algorithm and the high temporal resolution of the metasurface encoder, a three-dimensional ultrafast movie revealing information in (x, y, z, t) dimensions is computationally reconstructed for an ultrafast non-periodic event, which is previously not possible.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.