Astrophotonics (AP)
Design, simulation and characterization
Design, simulation and characterization of integrated photonic spectrographs for astronomy: generation-I AWG devices based on canonical layouts
Andreas Stoll; Kalaga V. Madhav; Martin M. Roth
We present an experimental study on our first generation of custom-developed arrayed waveguide gratings (AWG)
on a silica platform for spectroscopic applications in near-infrared astronomy. We provide a comprehensive
description of the design, numerical simulation and characterization of several AWG devices aimed at spectral
resolving powers of 15,000–60,000 in the astronomical H-band. We evaluate the spectral characteristics of the
fabricated devices in terms of insertion loss and estimated spectral resolving power and compare the results with
numerical simulations. We estimate resolving powers of up to 18,900 from the output channel 3-dB transmission
bandwidth. Based on the first characterization results, we select two candidate AWGs for further processing by
removal of the output waveguide array and polishing the output facet to optical quality with the goal of integration
as the primary diffractive element in a cross-dispersed spectrograph. We further study the imaging properties of the
processed AWGs with regards to spectral resolution in direct imaging mode, geometry-related defocus aberration, and
polarization sensitivity of the spectral image. We identify phase error control, birefringence control,
and aberration suppression as the three key areas of future research and development in the field of high-resolution
AWG-based spectroscopy in astronomy.
Journal Article