Ultrafast Imaging using Arrayed Quantum Detection Technologies (ULTRA-IMAGE)

视觉可以说是我们最重要的感官，也是我们与周围世界互动的最直接渠道。因此，影响我们日常生活的如此多的技术依赖于这样或那样的光也就不足为奇了。在不断努力改进我们的光源(从用于研究的激光到环境照明技术)的同时，从人工视觉植入物到高光谱成像，我们也在不断增加努力来提高我们的成像能力。一种令人兴奋的新兴成像技术依赖于检测非常微弱的光信号的能力，即甚至是单光子。这项同样的技术，例如基于单光子雪崩探测器(SPAD)的技术，伴随着另一个相当意想不到但也是显著的特征：令人难以置信的高时间分辨率和区分在时间上被皮秒或更短时间分开的事件的能力。这种时间分辨率是通过在所谓的时间相关单光子计数(TCSPC)模式下操作SPAD获得的，在TCSPC模式下，单个光子与外部触发器同时被探测到，然后以电子方式存储，在积累了许多事件后，可以精确地识别光子到达时间。这些技术现在已经相对成熟，并被常规用于研究活动，主要与量子光学测量和飞行时间测量有关。然而，这些探测器都是单像素探测器，因此不允许以与具有单像素的数码相机不产生图像大致相同的方式直接重建图像。已经采用了变通的解决方案；例如，激光可以扫描物体，单像素记录激光光束每个位置的强度水平。但是，我们对最新数码相机中的像素计数的痴迷清楚地解释了从单像素探测器到多像素探测器再到高分辨率成像的范式转变。Ultra IMAGE旨在展示非常新颖的SPAD技术的一系列应用：这些探测器首次可用于成像阵列。这是一项新兴技术，将代表成像领域的下一次革命，我们将第一手接触到SPAD阵列设计中的每一项技术突破，因为它们将在未来几年出现。我们目前正在使用32x32 SPAD阵列，并将使用有史以来(在撰写本文时)的第一个320x240像素阵列，它能够提供第一个高质量的空间分辨率图像。这些探测器的非凡之处在于，它们仍然保持着皮秒的时间分辨率，因此能够实现一系列改变游戏规则的非凡技术应用，这是传统相机无法想象的。作为这种新成像技术潜力的例子，我们将利用我们的SPAD相机来可视化光的传播，并对恶劣环境中的远程物体进行飞行时间检测(飞微微相机)，实现对隐藏在视野中的物体的实时跟踪(角落相机)，并使用低重复率、高功率激光(量子相机)执行第一次量子测量。我们将开发的解决方案由四个关键特性支持：第一，硅探测器的单光子灵敏度；第二，探测器阵列性质提供的空间分辨率；第三，精确的皮秒和飞秒时间分辨率；以及第四，门控检测的超低噪声性能。

Vision is arguably the most important of our senses and our most direct channel of interaction with the surrounding world. It is no surprise therefore that so much of the technology that affects our everyday lives relies on light in one form or the other. The continuous strive to improve our light sources, ranging from lasers for research purposed to ambient lighting technologies is paralleled by a continuous increase in efforts to improve our imaging capabilities, ranging from artificial vision implants to hyperspectral imaging. An exciting and emerging imaging technology relies on the ability to detect remarkably low light signals, i.e. even single photons. This same technology, based for example of Single-Photon-Avalanche-Detectors (SPADs) comes hand in hand with another rather unexpected and also remarkable feature: incredibly high temporal resolution and the ability to distinguish events that are separated in time by picoseconds or less. This temporal resolution is obtained by operating the SPAD in so-called Time-Correlated-Single-Photon-Counting (TCSPC) mode, where the single photons are detected in coincidence with an external trigger and then electronically stored with a precise time-tag that, after accumulating over many events, allows to precisely identify the photon arrival time.These technologies are now relatively well established and are routinely employed in research activities, mainly associated to quantum optics measurements and time of flight measurements. However, these detectors are all single pixel detectors and thus do not allow to directly reconstruct an image in much the same way that a digital camera with a single pixel will not create an image. Workaround solutions have been adopted; for example a laser may be scanned across an object and the single pixel records intensity levels for each position of the laser beam.However, our obsession with the pixel-count in our latest digital camera clearly explains the paradigm shift in going from a single pixel detector to a multi-pixel detector and eventually to high resolution imaging. ULTRA-IMAGE aims at demonstrating a series of applications of very novel SPAD technology: for the first time these detectors are available in imaging arrays. This is an emerging technology that will represent the next revolution in imaging and we will have first hand access to each technological breakthrough in SPAD array design, as they occur over the next few years. We are currently employing 32x32 SPAD arrays and will be using the first ever (at the time of writing) 320x240 pixel array, which is able to deliver the first high quality spatially resolved images. The remarkable aspect of these detectors is that they still retain their picosecond temporal resolution therefore enabling a series of game-changing and remarkable technological applications that are not even conceivable with traditional cameras.As examples of the potential of this new imaging technology, we will utilise our SPAD cameras to visualise the propagation of light and perform time-of-flight detection of remote objects in harsh environments (the FEMTO-camera), to enable of the real-time tracking of objects hidden from view (the CORNER-camera), and to perform the first quantum measurements using low-rep rate, high-power lasers (the QUANTUM-camera). The solutions we will develop are enabled by four key features: first, the single-photon sensitivity of silicon detectors; second, the spatial resolution provided by the arrayed nature of the detectors; third, the precise picosecond and femtosecond timing resolution; and fourth, the ultra low-noise performance of gated detection.