Using astrophotonics to design new components for future telescopes

With the Extremely Large Telescopes (ELTs) currently under construction we are entering a new era of challenging requirements, which drive spectrograph designs towards techniques that more efficiently use a facility's light feed. If the spectrograph can operate close to the diffraction limit, this reduces the footprint of the instrument compared to a conventional high resolution spectrograph and mitigates problems and cost issues caused by the use of large optics. By using adaptive optics (AO) to address the wavefront distortions caused by the Earth's atmospheric turbulence, we can provide diffractionlimited starlight to the telescope's focal plane. Using astrophotonic spatial reformatters and custom optical fibers to manage the AO output, we can increase the starlight coupled into the instrument. In the ?rst part of the thesis, simulation models are compared to manufactured and on-sky tested astrophotonic reformatters. Re-designing of the structures allowed their simulated performance to be further optimised. This is complemented by the laboratory characterisation of multiple different reformatters. In the second part of the thesis, everything discussed thus far is combined, leading to the design, manufacture and on-sky test of a novel instrument concept. This new instrument is composed of a multi-core fiber (MCF) with 3D printed micro-optics on its cores, which increase the coupling of light into them. The custom fiber is used to feed starlight from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument at the 8.2 m Subaru telescope in Hawaii to a diffraction-limited high resolution spectrograph. The results are promising and highlight the instrument's potential to change the paradigm with which high resolution spectrographs are built, in particular in the near infrared (NIR), for telescopes equipped with powerful AO systems. This study complements recent work in the field and provides crucial insight for optimising future astrophotonic devices.