Astrophotonic applications of ultrafast laser inscription

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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.