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

Gatkine, Pradip and Jovanovic, Nemanja and Jewell, Jeffrey and Wallace, J. Kent and Mawet, Dimitri (2021) An on-chip astrophotonic spectrograph with a resolving power of 12,000. In: UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts X. Proceedings of SPIE. No.11819. Society of Photo-Optical Instrumentation Engineers , Bellingham, WA, Art. No. 118190I.

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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.

Item Type:Book Section
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URLURL TypeDescription Paper
Gatkine, Pradip0000-0002-1955-2230
Jovanovic, Nemanja0000-0001-5213-6207
Wallace, J. Kent0000-0001-5299-6899
Mawet, Dimitri0000-0002-8895-4735
Additional Information:© 2021 Society of Photo-Optical Instrumentation Engineers (SPIE). Pradip Gatkine was supported by the David and Ellen Lee Postdoctoral Fellowship at the California Institute of Technology. Nemanja Jovanovic acknowledges the help and expertise of BRIGHT Photonics and Ligentec in the design and fabrication of one of the chips tested in this work as part of their MPW service. This work was supported by the Wilf Family Discovery Fund in Space and Planetary Science, funded by the Wilf Family Foundation. This research was carried out at the California Institute of Technology and the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration (NASA) and funded through the President’s and Director’s Research & Development Fund Program.
Group:Astronomy Department
Funding AgencyGrant Number
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
Wilf Family FoundationUNSPECIFIED
JPL President and Director's FundUNSPECIFIED
Subject Keywords:Photonic spectrograph, Arrayed Waveguide Gratings, Silicon Nitride, Integrated Spectrograph, Astrophotonics, Near-IR
Series Name:Proceedings of SPIE
Issue or Number:11819
Record Number:CaltechAUTHORS:20220610-860340600
Persistent URL:
Official 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);
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115117
Deposited By: Tony Diaz
Deposited On:10 Jun 2022 21:55
Last Modified:13 Jun 2022 16:53

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