Exoplanets & Exomoons

Simulating The Study Of Exoplanets Using Photonic Spectrographs

By Keith Cowing
March 23, 2022
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Simulating The Study Of Exoplanets Using Photonic Spectrographs
Left: CAD of the AWG, Right: Transmission response of the AWG in the form of Transmission in decibels (dB) as a function of wavelength.

Photonic spectrographs offer a highly miniaturized, flexible, and stable on-chip solution for astronomical spectroscopy and can be used for various science cases such as determining the atmospheric composition of exoplanets to understand their habitability, formation, and evolution.

Arrayed Waveguide Gratings (AWGs) have shown the best promise to be used as an astrophotonic spectrograph. We developed a publically-available tool to conduct a preliminary examination of the capability of the AWGs in spectrally resolving exoplanet atmospheres.

We derived the Line-Spread-Function (LSF) as a function of wavelength and the Full-Width-at-Half-Maximum (FWHM) of the LSF as a function of spectral line width to evaluate the response of a discretely- and continuously-sampled low-resolution AWG (R ∼ 1000). We observed that the LSF has minimal wavelength dependence (∼5\%), irrespective of the offset with respect to the center-wavelengths of the AWG channels, contrary to the previous assumptions. We further confirmed that the observed FWHM scales linearly with the emission line width.

Finally, we present simulated extraction of a sample molecular absorption spectrum with the discretely- and continuously-sampled low-resolution AWGs. From this, we show that while the discrete AWG matches its expected resolving power, the continuous AWG spectrograph can, in principle, achieve an effective resolution significantly greater (∼ 2x) than the discrete AWG. This detailed examination of the AWGs will be foundational for future deployment of AWG spectrographs for astronomical science cases such as exoplanet atmospheres.

Marcos Perez, Pradip Gatkine, Nemanja Jovanovic, Jeffrey Jewell, J. Kent Wallace, Dimitri Mawet

Comments: 13 pages, 6 figures, Presented at and published in the proceedings of SPIE Photonics West 2022
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Detectors (physics.ins-det); Optics (physics.optics)
Cite as: arXiv:2203.10153 [astro-ph.IM] (or arXiv:2203.10153v1 [astro-ph.IM] for this version)
Journal reference: Proc. SPIE 12008, Photonic Instrumentation Engineering IX, 120080C (Presented at SPIE OPTO: 5 March 2022; Published: 5 March 2022)
Submission history
From: Pradip Gatkine
[v1] Fri, 18 Mar 2022 20:40:19 UTC (1,570 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻