I read with interest the July 2016 article on sodium guide star lasers at the ESO Very Large Telescope in the Atacama Desert, Northern Chile, by Martin Enderlein, Wilhelm G. Kaenders, and Domenico Bonaccini Calia. The authors describe a third-generation laser system comprised of a distributed-feedback (DFB) diode laser oscillator, Raman fiber amplifiers, and frequency doubling.
The aim of this letter is simply to add a historical footnote on the laser development aspects of laser guide star emission. In addition to the references quoted in the article, the high-power tunable laser work of Everett and colleagues in the mid- to late-1980s,1-3 working at the MIT Lincoln Laboratory, should be mentioned. Albeit the exact guide star application was not explicitly mentioned in the Everett papers, perhaps given the cloak of secrecy surrounding high-power laser research during the SDI era, some key words provide significant clues. These words are: field location,1 elevated altitude,2 and atmospheric.3 The nexus between Everett's research to beacon star, laser guide star, and large telescopes was made explicit by Primmerman et al.4 in 1991. This type of research was also in progress at other locations in the U.S., including Lawrence Livermore. In this regard, the use of high-power narrow-linewidth tunable dye lasers in laser guide star applications was disclosed in the open literature in 1992.5
From a more general perspective, the introduction of adaptive optics concepts to astronomy might be traced back to a paper by Dyson6 and references therein.
REFERENCES
1. P. N. Everett et al., "Engineering of a multi-beam 300 W flashlamp-pumped dye laser system," Proc. Int. Conf. Lasers '87, 291–296 (1988).
2. P. N. Everett, "300 watt dye laser for field experimental site," Proc. Int. Conf. Lasers '88, 404–409 (1989).
3. P. N. Everett, "Flashlamp-excited dye lasers," High-Power Dye Lasers, Springer, Heidelberg, Germany (1991).
4. C. A. Primmerman et al., Nature, 353, 141–143 (1991).
5. I. L. Bass et al., Appl. Opt., 31, 6993–7006 (1992).
6. F. J. Dyson, J. Opt. Soc. Am., 65, 551–558 (1975).