Arrayed waveguide grating spectrometers for astronomical applications: new results
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 (${\lambda}/{\delta}{\lambda}$) 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.
- Publication:
-
Optics Express
- Pub Date:
- July 2017
- DOI:
- 10.1364/OE.25.017918
- arXiv:
- arXiv:1707.03445
- Bibcode:
- 2017OExpr..2517918G
- Keywords:
-
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Physics - Instrumentation and Detectors;
- Physics - Optics
- E-Print:
- Accepted at Optics Express, Special Issue on Astrophotonics (18 pages, 10 figures)