Photometric and Spectroscopic Superconducting Imaging Technology for Astrophysics

电磁波谱的亚毫米波（3 mm-300 um）和远红外（300 um-20 um）区域对天文学非常重要，因为它们包含了大量关于冷的、光学上黑暗的宇宙的信息。例如，宇宙微波背景辐射，这是大爆炸的遗迹，可以在最长的波长处找到，而来自遥远的，高度红移的星系的热辐射可以在最短的波长处找到。这些区域还包含来自许多分子和原子物种的数千条光谱线，这对于研究恒星和行星形成区域的化学和物理非常重要。在亚毫米波长上进行天文学观测异常困难，因为观测必须从偏远地区的高干旱地点或空间进行。信号的探测需要大型而昂贵的望远镜，复杂的仪器必须冷却到4K到100 mK之间的温度。购买合适的相机和光谱仪是不可能的，相反，天文学家必须开发自己的成像技术。拟议的方案旨在通过用超导体材料制造微型电路，开发新一代极灵敏的探测器和接收器。超导体具有这样的性质，即在临界温度以下，它们的电阻福尔斯降到零，并且磁通量被排出。事实上，超导态是一种独特的物质状态，它有许多奇怪的性质。通过由Nb、Ta、Al、Mo、NbN和NbTiN制造微电路，并通过使用现代Si和SiN微机械加工技术，可以制造具有非凡特性的探测器。例如，我们的一些红外探测器能够在1000万英里的距离上检测灯泡的开启和关闭，而其他探测器则以真正的量子力学方式工作，显示出非经典转换增益和受海森堡不确定性原理限制的灵敏度。（i）过渡边缘传感器（TES），其通过使用超导体到其正常状态的急剧过渡来操作，以测量当红外功率被微小的独立式微加工SiN岛吸收时发生的温度的微小变化;（二）动态电感探测器，主要测量当光子被吸收时磁场穿透进入超导体表面的量的微小变化;（三）超导体绝缘体超导体（SIS）混频器，使用极薄的超导和绝缘材料层制造二极管，其中发生量子力学隧道效应，制造高度灵敏的无线电接收器。这些设备类型中的每一种都可以单独使用或打包成多个像素的阵列以形成相机。超导混频器需要称为本地振荡器的相干锁相参考源，这在超太赫兹频率下非常难以实现。因此，发展适当的相干光源技术是我们方案的一个重要组成部分。我们提出的工作的另一个创新部分是开发微观图案化的声子滤波器，通过形成衰减支撑结构中的弹性波的滤波器来控制设备上的热流，并减少热波动噪声。我们提出的量子传感器物理学研究的核心主题本质上是智力上富有成果的，并且对于实现天文学的主要领域至关重要。在工作结束时，我们将展示基于先进超导设备的新一代成像技术，这些设备将可用于建造下一代地基和空间天文学所需的高灵敏度亚毫米波和远红外仪器。

The submillimetre-wave (3mm-300um) and far-infrared (300um-20um) regions of the electromagnetic spectrum are of considerable importance for astronomy because they contain a wealth of information about the cool, optically dark Universe. For example, the Cosmic Microwave Background radiation, which is a relic of the Big Bang, can be found at the longest wavelengths, and thermal radiation from distant, highly redshifted galaxies can be found at the shortest wavelengths. These regions also contain thousands of spectral lines from numerous molecular and atomic species, which are important for studying the chemistry and physics of regions where stars and planets are being formed. It is exceptionally difficult to carry out astronomy at submillimetre wavelengths because observations must be made from high dry sites in remote places or from space. The detection of signals requires large and expensive telescopes, and complex instruments must be cooled to temperatures of between 4K and 100 mK. It is simply not possible to buy suitable cameras and spectrometers, and instead astronomers must develop their own imaging technology. The proposed programme aims to develop a new generation of extremely sensitive detectors and receivers by fabricating microcircuits out of materials called superconductors. Superconductors have the property that their electrical resistance falls to zero below a critical temperature, and magnetic flux is expelled. Indeed, the superconducting state is a distinct state of matter, which has many curious properties. By fabricating microcircuits from Nb, Ta, Al, Mo, NbN and NbTiN and by using modern Si and SiN micromachining techniques, it is possible to make detectors having extraordinary characteristics. For example, some of our infrared detectors are capable of sensing a light bulb being turned on and off for just 1 second at a distance of 10 million miles, whilst others operate in a truly quantum mechanical way, displaying non-classical conversion gain and sensitivities limited by the Heisenberg uncertainty principle. The programme described in this application concentrates on three specific devices: (i) Transition Edge Sensors (TESs), which operate by using the sharp transition of a superconductor, to its normal state, to measure the minute change in temperature that occurs when infrared power is absorbed by a tiny free-standing micro-machined SiN island; (ii) Kinetic Inductance Detectors (KIDs), which essentially measure a small change that occurs in the amount by which magnetic field penetrates into the surface of a superconductor when photons are absorbed; (iii) Superconductor Insulator Superconductor (SIS) mixers, which use extremely thin layers of superconducting and insulating material to create diodes, in which quantum mechanical tunnelling occurs, creating highly sensitive radio receivers. Each of these device types can be used singly or packed into arrays of multiple pixels to form cameras. Superconducting mixers require coherent, phased locked reference sources called local oscillators, which are extremely difficult to realise at supra-THz frequencies. The development of suitable coherent source technology is therefore an essential part of our programme. Another innovative part of our proposed work is to develop microscopically patterned phononic filters that control the flow of heat onto devices, and reduce thermal fluctuation noise, by forming filters that attenuate elastic waves in support structures. The core themes of our proposed research into quantum sensor physics are intrinsically intellectually fruitful, and are of central importance to enabling major areas of astronomy. At the end of the work, we will have demonstrated a new generation of imaging technology based on advanced superconducting devices that will be available to construct the highly sensitive submillimetre-wave and far-infrared instruments needed for the next generation of ground-based and space-borne astronomy.