Redesign of the Integrated Photonic Spectrograph for Improved Astronomical Performance

The Integrated Photonic Spectrograph (IPS) is a complete spectrograph within a single silica photonic chip, that has no moving parts, is highly resistant to stress and temperature induced flexure and is far smaller than existing bulk-optic spectrographs. There has been considerable development in this all-photonic approach, culminating in a recent successful on-telescope test, which saw the world's first astronomical spectra taken using a photonic spectrograph. However, the device's performance (in terms of resolving power and wavelength coverage) was limited by the predominantly telecommunications-grade design parameters used in chip manufacturing, and at this stage warrants a substantial redesign of the arrayed waveguide grating structure inside the IPS chips, to optimize it for astronomy. In this body of work we present a comprehensive redesign of arrayed waveguide grating chips to improve specific performance parameters of interest to astronomy. These include the free-spectral range, resolving power and the operational wavelength for the devices, with an analysis of the limitations and benefits of the redesigns for typical astronomical goals. We propose how the redesigns, along with other advancements in astrophotonics, can be used in conjunction with adaptive-optics systems to make a prototype instrument with competitive throughput and resolving power.