Astrophotonic applications of ultrafast laser inscription

天文学正处于一场革命的边缘。大型望远镜，如42米的欧洲极大望远镜（E-ELT），正在计划中，这将使天文学家能够比以往任何时候都更深入地观察宇宙。使用这些望远镜进行的观测将用于回答从暗物质到外星生命等主题的问题。望远镜只是这幅图像的一部分，然而，需要新的仪器来分析它们收集的光线。按比例扩大旧的仪器技术将导致大型和昂贵的仪器，并重新思考如何建造这样的仪器是必要的。几十年来，研究人员一直在开发紧凑的光子器件，电子器件的光学模拟，主要用于电信应用。为了解决一些仪器问题，科学家和工程师们正在研究将光子概念应用于天文仪器的可能性。因此，近年来出现了天体光子学领域-它有可能彻底改变天文学。毫不奇怪，天文学的需求与电信业的需求不同。例如，电信设备已经被精细地调谐为使用在其空间属性方面高度受控的光在窄光谱区域上操作。相比之下，天文光子装置将需要在很宽的光谱范围内工作，进入装置的光的空间特性将根据观测对象和观测站的天气条件而变化。因此，很明显，虽然天体光子学可以从光子学社区的经验中受益，但天体光子学将需要开发全新的光子器件。由于天文学的独特要求，设想许多天文光子器件必须是三维的（3D）。鉴于几乎所有的当前制造技术都限于二维平面器件的制造，这提出了相当大的挑战。近年来，一种新的制造技术，超快激光雕刻（ULI），已经出现，使复杂的3D光子器件的制造。ULI使用持续时间< 1.0 ps的极短激光脉冲来局部修改透明材料（如玻璃）的结构。诱导的改性以多种方式表现出来，其示例包括改性材料的折射率或对化学蚀刻的敏感性的变化。使用这些表现形式，3D光子结构，如微光学，微机械和光波导-以类似于金属线引导电的方式引导光，可以通过将其在3D中平移通过激光焦点直接刻在材料中。因此，ULI是一种革命性的3D光子器件制造技术，可用于创建3D天文光子器件。该奖学金的目的是证明ULI是实现3D天文光子器件的最有前途的方法。为实现这一目标，将开发三种有针对性的天文学应用设备，并与天文学家合作，利用这些设备在世界各地的望远镜上进行真实的观测。第一个装置是一种新型的过滤器，它将从望远镜捕获的星光中去除地球大气层产生的光。第二种是微机械光纤开关。这种开关将用于未来的望远镜，使用数千根光纤来捕获望远镜聚焦的光线。第三个是3D光子光束组合器，它将用于联合收割机将多个望远镜捕获的光进行组合，从而显著提高所获得图像的空间分辨率。如果成功的话，这个奖学金将大大有助于天文仪器的范式转变，开辟了关于我们宇宙的突破性发现的道路。

Astronomy is on the brink of a revolution. Massive telescopes, such as the 42 m European Extremely Large Telescope (E-ELT), are being planned that will enable astronomers to peer farther into the universe than ever before. The observations performed using these telescopes will be used to answer questions on topics ranging from dark matter to extraterrestrial life. The telescopes are just one part of the picture however, new instruments are required to analyse the light collected by them. Scaling up the old instrumentation technology would result in large and costly instruments and a re-think about how such instruments will be constructed is required. For decades, researchers have been developing compact photonics devices, the optical analogue of electronic devices, mainly for applications in telecoms. To answer some of the instrumentation issues, scientists and engineers are now investigating the possibility of applying photonic concepts to astronomical instrumentation. Thus, the field of astrophotonics has emerged over recent years - it has the potential to revolutionise astronomy. Unsurprisingly, the demands of astronomy are different from those of telecoms. For example, telecom devices have been finely tuned to operate over a narrow spectral region using light that is highly controlled in terms of its spatial properties. In contrast, astrophotonic devices will be required to operate over a wide spectral range and the spatial properties of light entering the device will change depending on the subject of observation and the weather conditions at the observatory. It is clear therefore that although astrophotonics can benefit from the experience of the photonics community; astrophotonics will require the development of entirely new photonic devices. Due to the unique requirements of astronomy it is envisaged that many astrophotonic devices must be three-dimensional (3D). Given that almost all current fabrication technologies are limited to the fabrication of two-dimensional planar devices this presents a considerable challenge. Over recent years a new fabrication technology, ultrafast laser inscription (ULI), has emerged that enables the fabrication of complex 3D photonic devices. ULI uses extremely short laser pulses, with temporal durations < 1.0 ps, to locally modify the structure of transparent materials such as glass. The induced modification manifests itself in a plethora of ways, examples of which include changes in the refractive index or susceptibility to chemical etching of the modified material. Using these manifestations, 3D photonic structures such as micro-optics, micro-mechanics and optical waveguides - which guide light in a manner similar to the way metallic wires guide electricity, can be directly inscribed in the material by translating it in 3D through the laser focus. ULI is therefore a revolutionary 3D photonic device fabrication technology that can be used to create 3D astrophotonics devices. The objective of this fellowship is to demonstrate that ULI is the most promising way to realise 3D astrophotonic devices. This objective will be achieved by developing three devices for targeted astronomy applications and using them for real observations on telescopes around the world in collaboration with astronomers. The first device is a new type of filter that will remove the light generated by the earth's atmosphere from the starlight captured by the telescope. The second is a micro-mechanical fibre-optic switch. This switch will be used on future telescopes employing thousands of optical fibres to capture the light focussed by the telescope. The third is a 3D photonic beam combiner which will be used to combine the light capture by multiple telescopes, dramatically increasing the spatial resolution of the obtained images. If successful, this fellowship will contribute significantly to a paradigm shift in astronomical instrumentation, opening the way to ground breaking discoveries about our universe.