Fiber laser
4555508
216067857
2008-05-30T22:56:00Z
Dicklyon
869314
Reverted 1 edit by [[Special:Contributions/206.207.51.13|206.207.51.13]]. ([[WP:TW|TW]])
{{Copyedit|date=September 2007}}
A '''fiber laser''' or '''fibre laser''' is a [[laser]] in which the [[active gain medium]] is an [[optical fiber]] doped with [[rare-earth element]]s such as [[erbium]], [[ytterbium]], [[neodymium]], [[dysprosium]], [[praseodymium]], and [[thulium]]. They are related to [[Optical amplifier#Doped fibre amplifiers|doped fiber amplifiers]], which provide light amplification without lasing. Fiber [[Nonlinear Optics|nonlinearities]], such as [[Raman scattering| stimulated Raman scattering]] or [[four-wave mixing]] can also provide gain and thus serve as gain media for a fiber laser.
==Applications==
Applications of fiber lasers include [[laser ablation|material processing]], [[telecommunications]], [[spectroscopy]], and [[medicine]].
The advantage of the fiber laser is that the light is already coupled into the fiber and can be easily delivered to a movable focusing element.
Such a coupling is important for laser cutting or laser welding or laser folding of metals and polymers.
==Design and manufacturing of fiber lasers==
{{see also|Laser construction}}
Unlike most other types of lasers, the [[laser cavity]] in fiber lasers is constructed monolithically by [[fusion splicing]] the different types of fibers; most notably [[Fiber Bragg Grating|fiber Bragg gratings]] replace here conventional [[dielectric mirror| dielectric mirrors]] to provide [[optical feedback]]. To pump fiber lasers, semiconductor [[laser diode]]s or other fiber lasers are used almost exclusively. Fiber lasers can have active regions several kilometers long, and can provide very high optical gain. They can support kilowatt levels of continuous output power because the fiber's high [[surface area]] to [[volume]] ratio which allows efficient cooling. The fiber [[waveguide|waveguiding]] properties reduce or remove completely thermal distortion of the optical path thus resulting in typically [[diffraction-limited]] high-quality optical beam. Fiber lasers are also compact compared to [[solid-state laser|rod]] or [[gas laser]]s of comparable power, as the fiber can be bent to small diameters and coiled. Other advantages include high vibrational stability, extended lifetime and maintenance-free [[turnkey]] operation.
===Double-clad fibers===
[[Image:RectaDFC.png|100px|thumb|leftt|[[Double-clad fiber]] ]]
{{main|Double-clad fiber}}
Many high-power fiber lasers are based on [[double-clad fiber]]. The gain medium forms the core of the fiber, which is surrounded by two layers of cladding. The lasing [[transverse mode|mode]] propagates in the core, while a [[multi-mode optical fiber|multimode]] pump beam propagates in the inner cladding layer. The outer cladding keeps this pump light confined. This arrangement allows the core to be pumped with a much higher power beam than could otherwise be made to propagate in it, and allows the conversion of pump light with relatively low [[radiance|brightness]] into a much higher-brightness signal. As a result, fiber lasers and amplifiers are occasionally referred to as "brightness converters."
There is an important question about the shape of the double-clad fiber; a fiber with circular symmetry seems to be the worst possible design<ref name=bedo>{{cite journal| author=S. Bedo|coauthors= W. Luthy, and H. P. Weber |
title=The effective absorption coefficient in double-clad fibers|
journal=[[Optics Communications]]|
volume=99| issue=| pages=331–335| year=1993|
url=
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVF-46JGTGD-M5&_user=10&_coverDate=06%2F15%2F1993&_alid=550903253&_rdoc=1&_fmt=summary&_orig=search&_cdi=5533&_sort=d&_docanchor=&view=c&_ct=1&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c8a4c3ecc3d9a4e9ecb84f96cfef0333 |
doi=10.1016/0030-4018(93)90338-6}}
</ref><ref name="Liu">{{cite journal|
title=The absorption characteristics of circular, offset, and rectangular double-clad fibers|
author=A. Liu| coauthors= K. Ueda|
url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVF-497C4YV-BW&_user=10&_coverDate=12%2F15%2F1996&_alid=550869877&_rdoc=3&_fmt=summary&_orig=search&_cdi=5533&_sort=d&_docanchor=&view=c&_ct=3&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=688bbca25fdd98e29caadb676b003c1e
|journal=[[Optics Communications]]|
volume=132|
year=1996|
pages= 511–518|
doi=10.1016/0030-4018(96)00368-9}}
</ref><ref name="Kouznetsov2">{{cite journal|
title=Efficiency of pump absorption in double-clad fiber amplifiers. 2: Broken circular symmetry|
author= Kouznetsov, D.|
coauthors=Moloney, J.V.| journal=[[JOSAB]]|
url=http://josab.osa.org/abstract.cfm?id=68991|
volume=39 | year=2003 | issue=6 | pages=1259–1263|
doi=10.1364/JOSAB.19.001259}}</ref><ref name="Kouznetsov3">{{cite journal|
title=Efficiency of pump absorption in double-clad fiber amplifiers.3:Calculation of modes|
author= Kouznetsov, D.| coauthors=Moloney, J.V.|
journal=[[JOSAB]]|
url=http://josab.osa.org/abstract.cfm?id=68997|
volume=19 |year=2003 | issue=6 | pages=1304–1309|
doi=10.1364/JOSAB.19.001304}}
</ref><ref name="Doya"> {{cite journal|title=Modeling and optimization of double-clad fiber amplifiers using chaotic propagation of pump|
author= Leproux, P.| coauthors=S. Fevrier, V. Doya, P. Roy, and D. Pagnoux| journal=[[Optical Fiber Technology]]|
url=http://www.ingentaconnect.com/content/ap/of/2001/00000007/00000004/art00361|
volume=7 | year=2003 | issue=4 | pages=324–339|doi=10.1006/ofte.2001.0361}}</ref>
<ref name=boundary>{{cite journal|
title=Boundary behaviour of modes of a Dirichlet Laplacian|
author=D.Kouznetsov|coauthors=J.Moloney|
url=http://www.metapress.com/content/be0lua88cwybywnl/?p=6fbbaafc684541b28a96403556968148&pi=6|
journal=[[Journal of Modern Optics]]|
volume=51|
year=2004|
pages= 1362–3044 }}
</ref>. The design should allow the core to be small enough to support only a few (or even one) modes. It should provide sufficient cladding to confine the core and optical pump section over a relatively short piece of the fiber.
===Power scaling===
Recent developments in fiber laser technology have led to a rapid and large rise in achieved [[diffraction-limited]] beam powers from [[diode-pumped solid-state laser]]s. Due to the introduction of large mode area (LMA) fibers as well as continuing advances in high power and high brightness diodes, [[continuous-wave]] single-[[Transverse mode|transverse-mode]] powers from Yb-doped fiber lasers have increased from 100 W in 2001 to >1 kW.
Previously unattainable powers can now be achieved with commercially available off-the-shelf fibers and components. As a result, fiber laser technology is expected to have a profound effect on a broad variety of industrial applications. This white paper describes the technology in greater detail: "[http://www.nufern.com/whitepaper_detail.php/30 KW-power fiber lasers with single transverse mode output]".
==Fiber disk lasers==
[[Image:FiberDiskLasers.jpg|200px|right|thumb|3 fiber disk lasers]]
{{main|Fiber disk laser}}
Another type of fiber laser is the [[fiber disk laser]]. In such, the pump is not confined within the cladding of the fiber (as in the [[double-clad fiber]]), but pump light is delivered across the core multiple times because the core is coiled on itself like a rope. This configuration is suitable for [[power scaling]] in which many pump sources are used around the periphery of the coil. <ref name="UeL">{{cite journal| url=
http://www.maik.ru/cgi-bin/search.pl?type=abstract&name=lasphys&number=3&year=98&page=774
| author=K. Ueda| coauthors=A. Liu
| title=Future of High-Power Fiber Lasers
| journal=[[Laser Physics (Journal)|Laser Physics]]| volume=8| pages=774–781| year=1998}}</ref><ref name="fd1">
{{
cite journal
|url=http://ieeexplore.ieee.org/iel5/6572/17547/00811381.pdf
|author=K. Ueda
|title=Scaling physics of disk-type fiber lasers for kW output
|journal=Lasers and Electro-Optics Society
|volume=2
|pages=788-789
|year=1999
}}
</ref><ref name="kan">
{{
cite journal
|journal= Lasers and Electro-Optics Society 1999 12th Annual Meeting. LEOS '99. IEEE
|url=http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=811381&isnumber=17547
|author=Ueda
|coauthors= Sekiguchi H., Matsuoka Y., Miyajima H. , H.Kan
|title=Conceptual design of kW-class fiber-embedded disk and tube lasers
|year=1999
|volume=2
|pages=217-218}}
</ref><ref name="hamamatsu">{{cite journal
|journal=Nature Photonics sample
|url=http://www.nature.com/nphoton/journal/vsample/nsample/fig_tab/nphoton.2006.6_ft.html
|author=Hamamatsu K.K.
|title=The Fiber Disk Laser explained
|pages=14–15
|year=2006
|doi=10.1038/nphoton.2006.6
}}
</ref>
==See also==
*[[Double-clad fiber]]
*[[Fiber disk laser]]
==References==
{{reflist}}
<!--!-->
[[Category:Solid-state lasers]]
[[Category:Fiber optics]]
{{optics-stub}}
[[de:Faserlaser]]