Development of ultrafast laser inscribed astrophotonic components
Pike, Fraser Andrew
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The rapid development of astronomical instrumentation has been aided by many innovative new photonic designs, which offer improvements in stability, precision, size and cost, scalability, etc. ─ the field of astrophotonics. A powerful technique enabling many of these astrophotonic devices, ultrafast laser inscription (ULI), creates highly localised and controlled refractive index modification, which guides the path of light in a very efficient manner. This thesis discusses three separate astrophotonic devices, each with a specific application, to demonstrate the versatility of ULI. Firstly, a reformatting device based on a photonic lantern and 3D ULI waveguide reformatting component, transforms a multimode telescope PSF to a diffraction-limited pseudo-slit. When used to feed a spectrograph, a significant reduction in modal noise ─ a limiting factor in high-resolution multimode fibre-fed spectrographs ─ is demonstrated, with the potential for improved near-infrared radial velocity observations. Secondly, a similar ULI reformatting device for an integral field unit, based on multicore fibre with affixed microlenses, may enable the direct imaging of exoplanets and characterisation of their atmospheres. Thirdly, a two-telescope K-band beam combiner based on ULI directional couplers with an achromatic 3dB splitting ratio is presented. Such a device will upgrade the stellar interferometry capabilities of the CHARA array.