Thermal control of long delay lines in a high-resolution astrophotonic spectrograph

Gregory P. Sercel; Pradip R. Gatkine; Nemanja Jovanovic; Jeffrey B. Jewell; Luis Pereira da Costa; James Kent Wallace; Dimitri P. Mawet

doi:10.1117/12.3009916

12 March 2024 Thermal control of long delay lines in a high-resolution astrophotonic spectrograph

Gregory P. Sercel, Pradip R. Gatkine, Nemanja Jovanovic, Jeffrey B. Jewell, Luis Pereira da Costa, James Kent Wallace, Dimitri P. Mawet

Author Affiliations +

Proceedings Volume 12889, Integrated Optics: Devices, Materials, and Technologies XXVIII; 1288916 (2024) https://doi.org/10.1117/12.3009916
Event: SPIE OPTO, 2024, San Francisco, California, United States

Conference Poster

Abstract

High-resolution astronomical spectroscopy carried out with a photonic Fourier transform spectrograph (FTS) requires long asymmetrical optical delay lines that can be dynamically tuned. For example, to achieve a spectral resolution of R = 30,000, a delay line as long as 1.5 cm would be required. Such delays are inherently prone to phase errors caused by temperature fluctuations. This is due to the relatively large thermo-optic coefficient and long lengths of the waveguides, in this case composed of SiN, resulting in thermally dependent changes to the optical path length. To minimize phase error to the order of 0.05 radians, thermal stability of the order of 0.05° C is necessary. A thermal control system capable of stability such as this would require a fast thermal response and minimal overshoot/undershoot. With a PID temperature control loop driven by a Peltier cooler and thermistor, we minimized interference fringe phase error to +/- 0.025 radians and achieved temperature stability on the order of 0.05° C. We present a practical system for precision temperature control of a foundry-fabricated and packaged FTS device on a SiN platform with delay lines ranging from 0.5 to 1.5 cm in length using inexpensive off-the-shelf components, including design details, control loop optimization, and considerations for thermal control of integrated photonics.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Gregory P. Sercel, Pradip R. Gatkine, Nemanja Jovanovic, Jeffrey B. Jewell, Luis Pereira da Costa, James Kent Wallace, and Dimitri P. Mawet "Thermal control of long delay lines in a high-resolution astrophotonic spectrograph", Proc. SPIE 12889, Integrated Optics: Devices, Materials, and Technologies XXVIII, 1288916 (12 March 2024); https://doi.org/10.1117/12.3009916

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