Editing Optical amplifier (section)

==21st century==
In the 21st century high power [[fiber laser]]s were adopted as an industrial material processing tool, and were expanding into other markets including the medical and scientific markets. One key enhancement enabling penetration into the scientific market was improvement in high finesse fiber amplifiers, which became able to deliver single frequency linewidths (<5&nbsp;kHz) together with excellent beam quality and stable linearly polarized output. Systems meeting these specifications steadily progressed from a few watts of output power initially, to tens of watts and later hundreds of watts. This power increase was achieved with developments in fiber technology, such as the adoption of stimulated [[brillouin scattering]] (SBS) suppression/mitigation techniques within the fiber, and improvements in overall amplifier design, including large mode area (LMA) fibers with a low-aperture core,<ref>{{Cite journal|last1=Koplow|first1=Jeffrey P.|last2=Kliner|first2=Dahv A. V.|last3=Goldberg|first3=Lew|date=2000-04-01|title=Single-mode operation of a coiled multimode fiber amplifier|url=https://www.osapublishing.org/ol/abstract.cfm?uri=ol-25-7-442|journal=Optics Letters|language=EN|volume=25|issue=7|pages=442–444|doi=10.1364/OL.25.000442|pmid=18064073|bibcode=2000OptL...25..442K|osti=751138 |issn=1539-4794}}</ref> micro-structured rod-type fiber <ref>{{Cite journal|last1=Müller|first1=Michael|last2=Kienel|first2=Marco|last3=Klenke|first3=Arno|last4=Gottschall|first4=Thomas|last5=Shestaev|first5=Evgeny|last6=Plötner|first6=Marco|last7=Limpert|first7=Jens|last8=Tünnermann|first8=Andreas|date=2016-08-01|title=1 kW 1 mJ eight-channel ultrafast fiber laser|url=https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-15-3439|journal=Optics Letters|language=EN|volume=41|issue=15|pages=3439–3442|doi=10.1364/OL.41.003439|pmid=27472588|arxiv=2101.08498|bibcode=2016OptL...41.3439M|s2cid=11678581|issn=1539-4794}}</ref><ref>{{Cite journal|last1=Limpert|first1=J.|last2=Deguil-Robin|first2=N.|last3=Manek-Hönninger|first3=I.|last4=Salin|first4=F.|last5=Röser|first5=F.|last6=Liem|first6=A.|last7=Schreiber|first7=T.|last8=Nolte|first8=S.|last9=Zellmer|first9=H.|last10=Tünnermann|first10=A.|last11=Broeng|first11=J.|date=2005-02-21|title=High-power rod-type photonic crystal fiber laser|url=https://www.osapublishing.org/oe/abstract.cfm?uri=oe-13-4-1055|journal=Optics Express|language=EN|volume=13|issue=4|pages=1055–1058|doi=10.1364/OPEX.13.001055|pmid=19494970|bibcode=2005OExpr..13.1055L|issn=1094-4087|doi-access=free}}</ref> helical core,<ref>{{Cite journal|last1=Wang|first1=P.|last2=Cooper|first2=L. J.|last3=Sahu|first3=J. K.|last4=Clarkson|first4=W. A.|date=2006-01-15|title=Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser|url=https://www.osapublishing.org/ol/abstract.cfm?uri=ol-31-2-226|journal=Optics Letters|language=EN|volume=31|issue=2|pages=226–228|doi=10.1364/OL.31.000226|pmid=16441038|bibcode=2006OptL...31..226W|issn=1539-4794|url-access=subscription}}</ref> or chirally-coupled core fibers,<ref>{{Cite journal|last1=Lefrancois|first1=Simon|last2=Sosnowski|first2=Thomas S.|last3=Liu|first3=Chi-Hung|last4=Galvanauskas|first4=Almantas|last5=Wise|first5=Frank W.|date=2011-02-14|title=Energy scaling of mode-locked fiber lasers with chirally-coupled core fiber|url=https://www.osapublishing.org/oe/abstract.cfm?uri=oe-19-4-3464|journal=Optics Express|language=EN|volume=19|issue=4|pages=3464–3470|doi=10.1364/OE.19.003464|pmid=21369169|issn=1094-4087|pmc=3135632|bibcode=2011OExpr..19.3464L}}</ref> and '''tapered double-clad fibers''' (T-DCF).<ref>{{Cite journal|last1=Filippov|first1=V.|last2=Chamorovskii|first2=Yu|last3=Kerttula|first3=J.|last4=Golant|first4=K.|last5=Pessa|first5=M.|last6=Okhotnikov|first6=O. G.|date=2008-02-04|title=Double clad tapered fiber for high power applications|url=https://www.osapublishing.org/oe/abstract.cfm?uri=oe-16-3-1929|journal=Optics Express|language=EN|volume=16|issue=3|pages=1929–1944|doi=10.1364/OE.16.001929|pmid=18542272|bibcode=2008OExpr..16.1929F|issn=1094-4087|doi-access=free}}</ref> {{As of|2015}} high finesse, high power and [[Pulsed laser|pulsed]] fiber amplifiers delivered power levels exceeding those available from commercial solid-state single-frequency sources, and stable optimized performance, opening up new scientific applications.<ref>{{cite journal| title=High-power fiber amplifiers enable leading-edge scientific applications|last1 =Ding|first1=J.| last2 =Samson|first2= B.| last3 = Ahmadi|first3=P.|journal=Laser Focus World|via=Nufern Library| date=1 February 2015 | url=http://www.nufern.com/library/item/id/380/ | archive-url=https://web.archive.org/web/20151008224424/http://www.nufern.com/library/item/id/380/ | archive-date=8 October 2015 | url-status=deviated}}</ref>