Simulations of continuous-wave sodium laser guide stars with polarization modulation at Larmor frequency

2018 ◽  
Author(s):  
Felipe Pedreros Bustos ◽  
Ronald Holzlöhner ◽  
Domenico Bonaccini Calia ◽  
Joschua Hellemeier ◽  
Simon Rochester ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Larmor Frequency ◽  
Polarization Modulation ◽  
Laser Guide Stars ◽  
Laser Guide ◽  
Sodium Laser

Frequency chirped continuous-wave sodium laser guide stars: modeling and optimization

2020 ◽  
Vol 37 (4) ◽  
pp. 1208
Author(s):  
F. Pedreros Bustos ◽  
R. Holzlöhner ◽  
S. Rochester ◽  
D. Bonaccini Calia ◽  
J. Hellemeier ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Laser Guide Stars ◽  
Modeling And Optimization ◽  
Laser Guide ◽  
Sodium Laser

scholarly journals Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars

2009 ◽  
Vol 17 (7) ◽  
pp. 4920 ◽  
Author(s):  
Fabien Marc ◽  
Hugues Guillet de Chatellus ◽  
Jean-Paul Pique
Keyword(s):  
Laser Beam ◽  
Beam Propagation ◽  
Laser Beam Propagation ◽  
Laser Guide Stars ◽  
Spatial Shape ◽  
Laser Guide ◽  
Sodium Laser

The Four-Laser Guide Star Facility: Design considerations and system implementation

2014 ◽  
Vol 3 (3) ◽  
Author(s):  
Domenico Bonaccini Calia ◽  
Wolfgang Hackenberg ◽  
Ronald Holzlöhner ◽  
Steffan Lewis ◽  
Thomas Pfrommer
Keyword(s):  
Adaptive Optics ◽  
Technical Solution ◽  
Laser Guide Star ◽  
Laser Guide Stars ◽  
Very Large Telescope ◽  
Guide Star ◽  
Laser Guide ◽  
Sodium Laser ◽  
Optical Telescopes ◽  
Atmospheric Seeing

AbstractGround-based optical telescopes, in particular large ones, require adaptive optics to overcome the atmospheric seeing limit due to turbulence. Correcting the distorted wavefront necessitates bright stars in the field of view. The sky coverage can be greatly increased by using artificial sodium laser guide stars in addition to natural guide stars. We describe the underlying physics and technical considerations relevant to such systems before discussing the design of the four-laser guide star facility (4LGSF) which is currently under development for the ESO Very Large Telescope (VLT) on Cerro Paranal, Chile. The focus is upon the justification of the requirements and their technical solution.

scholarly journals Suppression of Rayleigh scattering noise in sodium laser guide stars by hyperfine depolarization of fluorescence

2006 ◽  
Vol 14 (24) ◽  
pp. 11494 ◽  
Author(s):  
Hugues Guillet de Chatellus ◽  
Ioana Moldovan ◽  
Vincent Fesquet ◽  
Jean-Paul Pique
Keyword(s):  
Rayleigh Scattering ◽  
Laser Guide Stars ◽  
Laser Guide ◽  
Sodium Laser ◽  
Scattering Noise

Diode-seeded fiber-based sodium laser guide stars ready for deployment

2010 ◽  
Author(s):  
Wilhelm G. Kaenders ◽  
Axel Friedenauer ◽  
Vladimir Karpov ◽  
Vladimir Protopopov ◽  
Wallace R. L. Clements ◽  
...  
Keyword(s):  
Laser Guide Stars ◽  
Laser Guide ◽  
Sodium Laser

scholarly journals Measuring line-of-sight sodium density structure using laser guide stars

2020 ◽  
Vol 494 (2) ◽  
pp. 2798-2808
Author(s):  
Joschua A Hellemeier ◽  
Domenico Bonaccini Calia ◽  
Paul Hickson ◽  
Angel Otarola ◽  
Thomas Pfrommer
Keyword(s):  
Adaptive Optics ◽  
Continuous Wave ◽  
Line Of Sight ◽  
Fibre Laser ◽  
Modulation Amplitude ◽  
Density Structure ◽  
Laser Guide Star ◽  
Laser Guide Stars ◽  
Guide Star ◽  
Laser Guide

ABSTRACT The performance of adaptive optics systems employing sodium laser guide stars can be improved by continuously monitoring the vertical density structure of mesospheric sodium along the line of sight. We demonstrate that sodium density profiles can be retrieved by amplitude modulation of continuous wave (CW) lasers. In an experiment conducted at the Large Zenith Telescope (LZT), ESO’s Wendelstein Raman-fibre laser was amplitude-modulated with a pseudo-random binary sequence and profiles were obtained by cross-correlation of the modulation pattern with the observed return signal from the laser guide star. For comparison, high-resolution profiles were obtained simultaneously using the lidar system of the LZT. The profiles obtained by the two techniques show noise contamination, but were found to agree to within the measurement error. As a further check, a comparison was also made between several lidar profiles and those obtained by simultaneous observations using a remote telescope to image the laser plume from the side. The modulated CW lidar technique could be implemented by diverting a small fraction of the returned laser light to a photon counting detector. Theoretical analysis and numerical simulations indicate that, for 50 per cent modulation strength, the sodium centroid altitude could be retrieved every 5 s from a single laser guide star, with an accuracy which would induce a corresponding wavefront error of 50 nm for the Extremely Large Telescope and less than 30 nm for the Thirty Meter Telescope and Giant Magellan Telescope. If multiple laser guide stars are employed, the required modulation amplitude will be smaller.

Toward optimization of pulsed sodium laser guide stars

2015 ◽  
Vol 32 (12) ◽  
pp. 2425 ◽  
Author(s):  
Rachel Rampy ◽  
Donald Gavel ◽  
Simon M. Rochester ◽  
Ronald Holzlöhner
Keyword(s):  
Laser Guide Stars ◽  
Laser Guide ◽  
Sodium Laser

scholarly journals Effects of Linewidth Broadening Method on Recoil of Sodium Laser Guide Star

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1315
Author(s):  
Xiangyuan Liu ◽  
Xianmei Qian ◽  
Rui He ◽  
Dandan Liu ◽  
Chaolong Cui ◽  
...  
Keyword(s):  
Spontaneous Emission ◽  
Continuous Wave ◽  
Laser Linewidth ◽  
Emission Rates ◽  
Laser Guide Star ◽  
Guide Star ◽  
Laser Guide ◽  
Sodium Laser ◽  
Linewidth Broadening ◽  
Multi Mode

The linewidth broadening of the circular-polarized continuous wave laser mitigates the recoil effects of the sodium laser guide star very well. By choice of the optimal laser linewidth, the relations between the laser intensity and average spontaneous emission rates are obtained. The numerically simulated results show that the 1–100 MHz linewidth broadening effectively weakens recoil and enhances the average spontaneous emission rates. For laser powers from 10 W to 60 W, considering the intensity distribution with random at the mesospheric sodium layer, when the laser linewidth is broadened to be 1–100 MHz from 0 MHz, increments of the return photons go up to 110% from 50% and do not have an effect on the spot sizes of the sodium laser guide star. Several cases have proven that the linewidth broadening method is correct. Further calculations show that the linewidth broadening method similarly applies to the case of the multi-mode laser. Furthermore, the linewidth broadening of re-pumping should be taken into account.

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