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许多技术都依赖于这种或那种形式的光，这并不奇怪。不断努力改善我们的光源，从用于研究目的的激光到环境照明技术，这与不断增加努力改善我们的成像能力相一致，从人工视觉植入到高光谱成像。一种令人兴奋的新兴成像技术依赖于检测非常低的光信号的能力，即甚至是单光子。同样的技术，例如基于单光子雪崩探测器（SPAD），与另一个相当意想不到的也是显著的功能：令人难以置信的高时间分辨率和区分在时间上以皮秒或更少间隔的事件的能力。这种时间分辨率通过在所谓的时间相关单光子计数（TCSPC）模式下操作SPAD来获得，其中单个光子与外部触发一致地被检测到，然后以电子方式存储有精确的时间标签，该精确的时间标签在经过许多事件累积之后允许精确地识别光子到达时间。这些技术现在已经相对完善地建立并且常规地用于研究活动中，主要涉及量子光学测量和飞行时间测量。然而，这些检测器都是单像素检测器，因此不允许以与具有单个像素的数码相机将不创建图像的方式大致相同的方式直接重建图像。解决方案已经被采用;例如，激光可以扫描物体，单个像素记录激光束每个位置的强度水平。然而，我们对最新数码相机像素数的痴迷清楚地解释了从单像素探测器到多像素探测器并最终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，我们将在未来几年内获得SPAD阵列设计中的每一项技术突破的第一手资料。我们目前采用32 x32 SPAD阵列，并将使用第一个（在撰写本文时）320 x240像素阵列，该阵列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传统相机无法想象的改变游戏规则和卓越的技术应用。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，并在恶劣的环境中对远程物体进行飞行时间探测（FEMTO相机），以实现从视图中隐藏的对象的实时跟踪（角落相机），并使用低重复率，高功率激光器（量子相机）执行第一次量子测量。我们将开发的解决方案有四个关键特性：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，精确的皮秒和飞秒定时分辨率;第四，门控探测的超低噪声性能。

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.