12 October 2024 Metasurface-based toroidal lenslet array design for addressing laser guide star elongation
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Abstract

The Giant Magellan Telescope will use laser tomography adaptive optics to correct for atmospheric turbulence using artificial guide stars created in the sodium layer of the atmosphere (altitude 90 km). The sodium layer has appreciable thickness (11 km), which results in the laser guide star being an elongated cylinder shape. Wavefront sensing with a Shack–Hartmann is challenging as subapertures located further away from the laser launch position image an increasingly elongated perspective of the laser guide star. Large detectors can be used to adequately pack and sample the images on the detector; however, this increases readout noise and limits the design space available for the wavefront sensor. To tackle this challenge, we propose an original solution based on nano-engineered meta-optics tailored to produce a spatially varying anamorphic image scale compression. We present meta-lenslet array designs that can deliver 100% of the full anamorphic image size reduction required for focal lengths down to 8 mm and a greater than 50% image size reduction for focal lengths down to 2 mm. This will allow for greatly improved sampling of the available information across the whole wavefront sensor while being a viable design within the limits of current-generation fabrication facilities.

© 2024 Society of Photo-Optical Instrumentation Engineers (SPIE)
Josephine Munro, Sarah E. Dean, Neuton Li, Israel J. Vaughn, Andrew W. Kruse, Tony Travouillon, Dragomir N. Neshev, Robert Sharp, and Andrey A. Sukhorukov "Metasurface-based toroidal lenslet array design for addressing laser guide star elongation," Journal of Astronomical Telescopes, Instruments, and Systems 10(4), 049002 (12 October 2024). https://doi.org/10.1117/1.JATIS.10.4.049002
Received: 28 April 2024; Accepted: 12 September 2024; Published: 12 October 2024
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KEYWORDS
Design

Lens arrays

Laser guide stars

Wavefront sensors

Sensors

Sodium

Spherical lenses

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