Laboratory demonstration of an alternative laser guide stars wavefront sensing technique—projected pupil plane pattern

Yang, Huizhe; Bharmal, Nazim Ali; Myers, R; Younger, Eddy

doi:10.1117/1.jatis.5.2.029002

Cited by 5 publications

(2 citation statements)

References 14 publications

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“…Sky-Projected Laser Array Shack-Hartmann (SPLASH) (Butterley et al 2006), the CAFADIS camera (Rodríguez-Ramos et al 2008), the Plenoptic WFS (Zhang et al 2021), or through a smart optical arrangements of the SH beams (Lombini et al 2022). Some configurations have been arranged on a laboratory breadboard, where the overall configuration is scaled down to a laboratory size (Yang et al 2019). Finally, some of them have been tested, albeit with some limitations (Bharmal et al 2018) and on the sky (Ragazzoni et al 2006).…”

Section: Description Of the Lgs In The Focal Volumementioning

confidence: 99%

Ingot-like class of wavefront sensors for laser guide stars

Ragazzoni,

Portaluri,

Greggio

et al. 2024

A&A

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Full sky coverage adaptive optics (AO) on extremely large telescopes requires the adoption of several laser guide stars as references. With such large apertures, the apparent elongation of the beacons is absolutely significant. With a few exceptions, wavefront sensors (WFSs) designed for natural guide stars can be adapted and used in suboptimal mode in this context. We analyse and describe the geometrical properties of a class of WFSs that are specifically designed to deal with laser guide stars propagated from a location in the immediate vicinity of the telescope aperture. We describe, in three dimensions, the loci where the light of the laser guide stars would focus in the focal volume located behind the focal plane where astronomical objects are reimaged. We also describe the properties of several types of optomechanical devices that act as perturbers for this new class of pupil plane sensors, through refraction and reflections. We refer to these as ingot WFSs. We provide the recipes both for the most reasonably complex version of these WFSs, with six pupils and, for the simplest one, only three pupils. Both of them are referred to on the basis of the European Extremely Large Telescope (ELT) case. We outlined elements that are meant to give a qualitative idea of how the sensitivity of this new class of sensors compares to conventional ones. We present a new class of WFSs, based on an extension to the case of elongated sources at a finite distance of the pyramid WFS. We point out which advantages of the pyramid can be retained and how it may be adopted to optimize the sensing procedure.

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Section: Description Of the Lgs In The Focal Volumementioning

confidence: 99%

Ingot-like class of wavefront sensors for laser guide stars

Ragazzoni,

Portaluri,

Greggio

et al. 2024

A&A

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“…The laser uplink is reconfigured depending on the WFS concept but the common factor is an emulation of atmospheric back-scattering from up to 20 km distance. Two emulation mechanisms will be available: using fluorescence to downshift the frequency or polarization-conserving scattering, 4,5 allowing separation of the laser uplink and downlink by wavelength or polarization, respectively. To verify these concepts' measurements, a standard WIVERN capability is the Shack Hartmann WFS to measure a constellation of point sources that simulates several, conventional, star-oriented WFSs.…”

Section: Introductionmentioning

confidence: 99%

WIVERN: a laboratory experiment for testing novel laser-based wavefront sensing techniques

Bharmal

Bramall

Rosario³

et al. 2022

Adaptive Optics Systems VIII

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WIVERN is a testbed for laboratory experiments in laser-based wavefront sensing. It emulates laser uplink from a 4 m telescope with 1.6 arcsec seeing and laser back-scattering from up to 20 km. Currently there are three current wavefront sensing capabilities. The first two are from a wide-field of view (1.0 arcmin) Shack Hartmann wavefront sensor observing a constellation of point sources at infinity (reference targets, star-oriented wavefront sensing), or an image from emulated back-scattering (wide-field correlation wavefront sensing). The third is based on the PPPP concept. Other sub-systems are laser projection replicating a pupil launch, a 7x7 pupil-conjugate deformable mirror (DM), and a wide-field camera for PSF analysis. A 500 Hz rate accumulates sufficient data for statistical and machine-learning analysis over hour timescales. It is a compact design (2.1 m 2 ) with mostly commercial dioptric components. The sub-system optical interfaces are identical: a flat focal plane for easy bench reconfiguration. The end-to-end design is diffraction-limited with ≤ 1% pupil distortion for wavelengths λ=633-750 nm.

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