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arXiv · 1707.03445

Arrayed Waveguide Grating Spectrometers for Astronomical Applications: New Results

Pradip Gatkine·Sylvain Veilleux·Yiwen Hu·Joss Bland-Hawthorn·Mario Dagenais
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Abstract

One promising application of photonics to astronomical instrumentation is the miniaturization of near-infrared (NIR) spectrometers for large ground- and space-based astronomical telescopes. Here we present new results from our effort to fabricate arrayed waveguide grating (AWG) spectrometers for astronomical applications entirely in-house. Our latest devices have a peak overall throughput of ~23%, a spectral resolving power ($λ/δλ$) of ~1300, and cover the entire H band (1450-1650 nm) for Transverse Electric (TE) polarization. These AWGs use a silica-on-silicon platform with a very thin layer of Si3N4 as the core of the waveguides. They have a free spectral range of ~10 nm at a wavelength of ~1600 nm and a contrast ratio or crosstalk of about 2% (-17 dB). Various practical aspects of implementing AWGs as astronomical spectrographs are discussed, including the coupling of the light between the fibers and AWGs, high-temperature annealing to improve the throughput of the devices at ~1500 nm, cleaving at the output focal plane of the AWG to provide continuous wavelength coverage, and a novel algorithm to make the devices polarization insensitive over a broad band. These milestones will guide the development of the next generation of AWGs with wider free spectral range and higher resolving power and throughput.

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Pradip Gatkine, Sylvain Veilleux, Yiwen Hu, Joss Bland-Hawthorn, Mario Dagenais. 2017-07-11. Arrayed Waveguide Grating Spectrometers for Astronomical Applications: New Results. https://doi.org/10.1364/oe.25.017918

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