Performance limits of astronomical arrayed waveguide gratings on silica platform

TL;DR

This study investigates how phase errors affect the performance of large astronomical arrayed waveguide gratings (AWGs) on silica platforms, demonstrating that post-processing can mitigate these errors for effective H-band spectroscopy.

Contribution

The paper combines numerical modeling, experimental measurements, and phase error correction techniques to determine the performance limits of silica AWGs in astronomy.

Findings

Phase errors can be effectively corrected through length trimming.

Post-processing eliminates phase errors as a performance bottleneck.

The phase-error limited size of AWGs is estimated for current fabrication technology.

Abstract

We present a numerical and experimental study of the impact of phase errors on the performance of large, high-resolution Arrayed Waveguide Gratings (AWG) for applications in astronomy. We use a scalar diffraction model to study the transmission spectrum of an AWG under random variations of the optical waveguide lengths. We simulate phase error correction by numerically trimming the lengths of the optical waveguides to the nearest integer multiple of the central wavelength. The optical length error distribution of a custom-fabricated silica AWG is measured using frequency-domain interferometry and Monte-Carlo fitting of interferogram intensities. In the end, we give an estimate for the phase-error limited size of a waveguide array manufactured using state-of-the-art technology. We show that post-processing eliminates phase errors as a performance limiting factor for astronomical spectroscopy in the H-band.