Editing Laser guide star (section)

==Laser development==
[[Dye laser]]s were the first laser sources used in laser guide star applications.<ref>{{cite journal |last1=Everett |first1=Patrick N. |date=1989 |title=300-Watt dye laser for field experimental site|journal=Proceedings of the International Conference on Lasers '88 |pages=404–9 |oclc=20243203 |osti=5416850|bibcode=1989lase.conf..404E}}</ref><ref>{{cite journal |pages=141–3 |doi=10.1038/353141a0|bibcode=1991Natur.353..141P |title=Compensation of atmospheric optical distortion using a synthetic beacon |date=1991 |last1=Primmerman |first1=Charles A. |last2=Murphy|first2=Daniel V. |last3=Page |first3=Daniel A. |last4=Zollars |first4=Byron G. |last5=Barclay |first5=Herbert T.|s2cid=4281137|journal=Nature |volume=353 |issue=6340}}</ref><ref>{{cite journal |pages=6993–7006 |doi=10.1364/AO.31.006993|bibcode=1992ApOpt..31.6993B |title=High-average-power dye laser at Lawrence Livermore National Laboratory |date=1992 |last1=Bass |first1=Isaac L. |last2=Bonanno|first2=Regina E. |last3=Hackel |first3=Richard P. |last4=Hammond |first4=Peter R. |journal=Applied Optics|volume=31 |issue=33 |pmid=20802559}}</ref><ref name="AO">{{cite journal |pages=3038–41 |doi=10.1364/AO.40.003038|bibcode=2001ApOpt..40.3038D |title=Multiple-Return-Pass Beam Divergence and the Linewidth Equation |date=2001 |last1=Duarte F. J.|journal=Applied Optics|volume=40 |issue=18 |pmid=18357323|author1-link=F. J. Duarte}}</ref>  These tunable lasers have continued to play a significant role in this field.<ref>{{cite journal |pages=2093–101 |doi=10.1364/JOSAB.20.002093 |bibcode=2003OSAJB..20.2093P |title=Efficient modeless laser for a mesospheric sodium laser guide star |date=2003 |last1=Pique |first1=Jean-Paul |last2=Farinotti |first2=Sébastien |journal=Journal of the Optical Society of America B |volume=20 |issue=10|url=https://hal.archives-ouvertes.fr/hal-01118356}}</ref><ref>{{cite journal |doi=10.1086/499290 |bibcode=2006PASP..118..297W |url=https://www2.keck.hawaii.edu/optics/aodocs/PWetal2006PASP118_297.pdf |title=The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Overview |date=2006|last1=Wizinowich |first1=Peter L. |last2=Le Mignant |first2=David |last3=Bouchez |first3=Antonin H.|last4=Campbell|first4=Randy D. |last5=Chin |first5=Jason C. Y. |last6=Contos |first6=Adam R. |last7=Van Dam |first7=Marcos A.|last8=Hartman |first8=Scott K. |last9=Johansson |first9=Erik M. |last10=Lafon |first10=Robert E. |last11=Lewis|first11=Hilton |last12=Stomski |first12=Paul J. |last13=Summers |first13=Douglas M. |last14=Brown |first14=Curtis G. |last15=Danforth|first15=Pamela M. |last16=Max |first16=Claire E. |last17=Pennington |first17=Deanna M. |journal=Publications of the Astronomical Society of the Pacific |volume=118 |issue=840 |pages=297–309|display-authors=8}}</ref> However, the use of fluid gain media has been considered by some researchers as disadvantageous.<ref>{{Citation|last1=Comaskey|first1=Brian|title=High average power laser gain medium with low optical distortion using a transverse flowing liquid host|date=Nov 6, 2003|url=https://patents.google.com/patent/US20030206568|last2=Ault|last3=Kuklo|first2=Earl|first3=Thomas|access-date=2016-03-19}}</ref> Second generation laser sources for sodium guide star applications include sum-frequency-mixed solid-state lasers.<ref>{{cite conference|last1=D'Orgeville|first1=Céline|author-link=Céline d'Orgeville|last2=Fetzer|first2=Gregory J.|date=2016|title=Four generations of sodium guide star lasers for adaptive optics in astronomy and space situational awareness|conference=Adaptive Optics Systems V|publisher=SPIE|volume=9909|bibcode=2016SPIE.9909E..0RD|doi=10.1117/12.2234298|isbn=9781510601970}}</ref> New third generation laser systems based on tunable diode lasers with subsequent narrow-band Raman fiber amplification and resonant frequency conversion have been under development since 2005. Since 2014  fully engineered systems are commercially available.<ref>{{cite web|title=SodiumStar 20/2 – High Power CW Tunable Guide Star Laser|url=https://www.toptica.com/fileadmin/Editors_English/11_brochures_datasheets/01_brochures/toptica_BR_SodiumStar.pdf|website=www.toptica.com|publisher=TOPTICA Photonics AG|accessdate=28 May 2019}}</ref> Important output features of the [[tunable laser]]s mentioned here include diffraction-limited beam divergence and narrow-linewidth emission.<ref name="AO" />