Photometric and Spectroscopic Superconducting Imaging Technology for Astrophysics

电磁波谱的微波（3厘米-3毫米）、亚毫米波（3毫米-300微米）和远红外（300微米-20微米）区域包含了大量关于寒冷、黑暗宇宙的信息。例如，宇宙微波背景辐射可以在最长的波长被发现，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被发现。这部分光谱还包含来自无数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。在亚毫米波段进行天文观测异常困难，因为观测必须在高干燥地点或太空进行。探测信号需要大型、精密的望远镜，复杂的仪器必须冷却到4 K到100 mK的温度。买到合适的相机和光谱仪是不可能的，因此天文学家必须开发自己的成像技术。该计划旨在通过超导体材料制造微电路，开发新一代微波、亚毫米波和远红外波长的极其灵敏的探测器和接收器。超导态是物质的一种独特的状态，它有许多奇怪的性质。通过用Nb、Ta、Al、Mo、NbN、TiN和NbTiN制造微电路，并使用现代Si和SiN微加工技术，可以制造出具有非凡特性的复杂电子器件。例如，我们的一些红外探测器能够在1000万英里的距离上感应到灯泡打开和关闭仅1秒钟，而其他探测器则以真正的量子力学方式运行，显示出受海森堡不确定性原理限制的非经典转换增益和灵敏度。本提案中描述的工作集中在四个特定设备上：(i)过渡边缘传感器（TESs），它通过超导体到其正常状态的急剧转变来工作，以测量红外功率被微小的独立微机械SiN膜吸收时发生的微小温度变化；（ii）动能电感探测器（KIDs），主要测量光子被吸收时磁场穿透超导体表面的量的微小变化；（三）参数放大器，利用某些超导材料的非线性特性实现超低噪声放大；超导体绝缘体超导体（SIS）混频器，它使用极薄的超导和绝缘材料层来制造二极管，在二极管中发生量子力学隧穿，从而产生高灵敏度的无线电接收器。这些设备中的每一个都可以单独使用，也可以打包成多个像素的阵列来形成相机。超导混频器需要称为本地振荡器的参考源，这在太赫兹频率下是极其难以实现的。因此，开发合适的相干源技术是我们计划的重要组成部分。我们提出的工作的另一个创新部分是开发微观图案声子滤波器，通过形成滤波器衰减支撑结构中的弹性波来控制设备上的热量流动，并减少热波动噪声。我们提出的量子传感器物理研究的核心主题本质上是富有成果的，并且对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各种新成像技术，该技术将用于构建下一代地基和天基天文学所需的高灵敏度仪器。

The microwave (3 cm-3 mm), submillimetre-wave (3 mm-300 um) and far-infrared (300 um-20 um) regions of the electromagnetic spectrum contain a wealth of information about the cool, dark Universe. For example, the Cosmic Microwave Background radiation can be found at the longest wavelengths, and thermal radiation from distant, highly redshifted galaxies can be found at the shortest wavelengths. This part of the spectrum also contains 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 formed. It is exceptionally difficult to carry out astronomy at submillimetre wavelengths because observations must be made from high dry sites or from space. The detection of signals requires large, precision telescopes, and complex instruments must be cooled to temperatures of between 4 K and 100 mK. It is simply not possible to buy suitable cameras and spectrometers, and so astronomers must develop their own imaging technology. The proposed programme aims to develop a new generation of extremely sensitive detectors and receivers for microwave, submillimetre-wave and far-infrared wavelengths by fabricating microcircuits out of materials called superconductors. The superconducting state is a distinct state of matter, which has many curious properties. By fabricating microcircuits from Nb, Ta, Al, Mo, NbN, TiN and NbTiN and by using modern Si and SiN micromachining techniques, it is possible to make complex electronic devices 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 work described in this proposal concentrates on four 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 membrane; (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) parametric amplifiers, which use the non-linear characteristics of certain superconducting materials to achieve ultra-low-noise amplification; (iv) 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 devices can be used singly or packed into arrays of multiple pixels to form cameras. Superconducting mixers require reference sources called local oscillators, which are extremely difficult to realise at 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 various new imaging technologies based on advanced superconducting devices, and this technology will then be available to construct the highly sensitive instruments needed for the next generation of ground-based and space-based astronomy.