Feasibility study of femtosecond laser written arrayed waveguide gratings for astronomy

This thesis studies the feasibility of femtosecond laser written array waveguide gratings (AWG) with an interest in astronomical applications. AWGs have recently been studied as a new integrated alternative to the current generation of astronomical spectographs. AWGs have the advantage of being small, robust and stable - all important factors sought after in astronomical instrumentation. One setback for the use of AWGs in astronomy is that current fabrication techniques are expensive and hard to prototype, making development of such devices difficult. This feasibility study has explored the possibility of fabricating AWGs using a laser direct write technique that is cheap and allows for fast design prototype. The femtosecond laser direct write technique uses a focused high powered laser to produce a localised refractive index change in a glass substrate which is typically used to form waveguides. To fabricate AWGs using the laser writing technique, the capability to inscribe large smooth planar waveguides that act as a 2D free propagation zones were evaluated. Once a suitable slab fabrication method was established a laser written AWG proto-type was produced with initial output showing a degree of correlation to the theoretical output at a single wave- length. From this initial proto-type design improvements were made to improve the device, however initial results shows that laser written AWGs are highly susceptible to phase array error which could affect the feasibility of laser written AWGs. This initial study shows that laser written AWGs could have future applications in telecommunications and integrated spectroscopic sensors when phase errors are minimised.