An on-chip astrophotonic spectrograph with a resolving power of 12,000

Pradip Gatkine; Nemanja Jovanovic; Jeffrey Jewell; J. Kent Wallace; Dimitri Mawet

doi:10.1117/12.2594635

20 August 2021 An on-chip astrophotonic spectrograph with a resolving power of 12,000

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

Proceedings Volume 11819, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts X; 118190I (2021) https://doi.org/10.1117/12.2594635
Event: SPIE Optical Engineering + Applications, 2021, San Diego, California, United States

Abstract

With the upcoming extremely large telescopes (ELTs), the volume, mass, and cost of the associated spectro- graphs will scale with the telescope diameter. Astrophotonics offers a unique solution to this problem in the form of single-mode fiber-fed diffraction-limited spectrographs on a chip. These highly miniaturized chips offer great flexibility in terms of coherent manipulation of photons. Such photonic spectrographs are well-suited to disperse the light from directly imaged planets (post-coronagraph, collected using a single-mode fiber) to characterize exoplanet atmospheres. Here we present the results from a proof-of-concept high-resolution astrophotonic spectrograph using the arrayed waveguide gratings (AWG) architecture. This chip uses the low-loss SiN platform (SiN core, SiO₂ cladding) with square waveguides (800 nm ~ 800 nm). The AWG has a measured resolving power (=) of ~ 12,000 and a free spectral range (FSR) of 2.8 nm. While the FSR is small, the chip operates over a broad band (1200 - 1700 nm). The peak on-chip throughput (excluding the coupling efficiency) is ~40% (- 4 dB) and the overall throughput (including the coupling loss) is ~ 11% (- 9.6 dB) in the TE mode. Thanks to the high-confinement waveguide geometry, the chip is highly miniaturized with a size of only 7.4 mm x 2 mm. This demonstration highlights the utility of SiN platform for astrophotonics, particularly, the capability of commercial SiN foundries to fabricate ultra-small, high-resolution, high-throughput AWG spectrographs on a chip suitable for astronomical applications.

Conference Presentation

Citation Download Citation

Pradip Gatkine, Nemanja Jovanovic, Jeffrey Jewell, J. Kent Wallace, and Dimitri Mawet "An on-chip astrophotonic spectrograph with a resolving power of 12,000", Proc. SPIE 11819, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts X, 118190I (20 August 2021); https://doi.org/10.1117/12.2594635

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