查看“︁光學渦旋”︁的源代码

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'''光學渦旋'''（optical vortex）也稱為'''光渦'''，是[[光學場]]中的[[零點]]，也就是光強度為零的點。自從{{le|約翰·奈|John Nye (scientist)}}和[[迈克尔·贝里]]在1974年提出全面性的論文後，就開始了許多光學渦旋性質的研究<ref>{{cite journal | last = Nye | first = J. F. |author2=M. V. Berry | year = 1974 | title = Dislocations in wave trains | journal = Proceedings of the Royal Society of London, Series A | volume = 336 | issue = 1605 | pages = 165–190 | url = http://rspa.royalsocietypublishing.org/content/336/1605/165.full-text.pdf | format = PDF | accessdate = 2006-11-28 | doi = 10.1098/rspa.1974.0012 |bibcode = 1974RSPSA.336..165N }}</ref>，論文描述「光波列位錯」的基本性質，這個研究後來成為「奇點光學」（singular optics）的核心理論。

==解釋==
在光學渦旋中，光會像螺旋開瓶器一般，沿著其軸扭轉。因為其扭轉，在軸的位置光會彼此相消。若投影在一平坦表面上，光學渦旋看起來會像一個光環，在中間有一個沒有光的黑色區域。這種螺旋形行進，中間黑暗的光，稱為光學渦旋。

光學渦旋的{{le|拓扑荷|topological charge}}定義為其在一個波長的扭轉次數，拓扑荷恆為整數，依其扭轉方向可能是正數或是負數。拓扑荷越大表示光沿著軸旋轉的越快。此自旋會隨著光波列而有角動量，若有[[電偶極矩]]則會產生[[力矩]]。

光的軌道角動量可以由捕獲粒子的軌道運動來觀察。光學渦旋和[[平面波|平面]]光的干涉會出現同心螺旋的螺旋相位。<!--The number of arms in the spiral equals the topological charge.-->

在實驗室中有許多方式可以產生光學渦旋。一般可以直接用[[雷射]]產生<ref name="jmo1991">{{cite journal|last=White|first=AG|author2=Smith, CP |author3=Heckenberg, NR |author4=Rubinsztein-Dunlop, H |author5=McDuff, R |author6=Weiss, CO |author7= Tamm, C |title=Interferometric measurements of phase singularities in the output of a visible laser|journal=Journal of Modern Optics|year=1991|volume=38|issue=12|pages=2531–2541|doi=10.1080/09500349114552651|bibcode=1991JMOp...38.2531W}}</ref>，或者用一些方式，將雷射光束變成渦旋，例如用電腦產生全息圖，螺旋相位延遲的結構，或是材料中的雙折射渦旋。

==性質==
光學奇點是光場中的零點。在場中的相位會沿著零強度的點旋轉（因此稱為渦旋）。光學渦旋在二維場中為一個點，在三維場中為一條線（其[[余維數]]為2）。將場中的相位沿著包圍渦流的路徑場積分，會得到2{{pi}}的整數倍。此整數稱為光學渦旋的拓扑荷或是強度。

超几何[[高斯光束]]（HyGG）在其中心有一個光學渦旋，光束的形式為

:<math> \psi\propto  e^{im\phi} e^{-r^2},\!</math>

為旁軸波動方程含有[[贝塞尔函数]]的解（參照[[近軸近似]]<!--, and the {{le|傅立葉光學|Fourier optics]] article for the [[Fourier optics#The paraxial wave equation|actual equation]]-->）。超几何高斯光束中的光子有軌道角動量''mħ''，其中的正整數''m''也就是光束中央渦旋的強度。圓偏振光的自旋角動量可以被轉換成軌道角動量<ref>{{cite journal |title=Optical spin-to-orbital angular momentum conversion in inhomogeneous anisotropic media |url=http://link.aps.org/abstract/PRL/v96/e163905 |journal=Physical Review Letters |volume=96 |year=2006 |doi=10.1103/PhysRevLett.96.163905 |pages=163905 |author=Marrucci, L. |pmid=16712234 |last2=Manzo |first2=C |last3=Paparo |first3=D |issue=16 |bibcode=2006PhRvL..96p3905M|arxiv = 0712.0099 }}</ref>。

==創造光學渦旋==
[[Image:opticalVortices.jpg|thumb|right|用計算機生成全息圖產生的光學渦旋]]

有許多的方式可以產生超几何[[高斯光束]]，[[靜態螺旋相位板]]（Static spiral phase plate, SPP）、電腦產生的[[全息摄影]]、[[模式轉換]]（Mode conversion）、{{le|q板|q-plate}}、s板、{{le|空間光調製器|spatial light modulator}}及{{le|可變形反射鏡|Deformable mirror}}等。

==應用==
光學渦旋可用在許多應用中，例如以往只能[[系外行星偵測法|直接偵測]]的[[太陽系外行星]]可以用[[旋風星冕儀]]觀測。[[光鑷]]可以用在處理像細胞大小的物體等，{{le|受激發射損耗顯微鏡|STED microscopy}}中也有到光學渦旋的技術。

== 相關條目 ==
* [[旋風星冕儀]]
* [[光鑷]]
* {{le|軌道角動量路復用|Orbital angular momentum multiplexing}}

==參考資料==
{{reflist}}

==外部連結==
* [http://www.youtube.com/watch?v=kNtN6TRFvsE Video of propagation simulation of Vortex Diffractive Optical Element from near field to far field]{{Wayback|url=http://www.youtube.com/watch?v=kNtN6TRFvsE |date=20160810150924 }} by HoloOr 
* [https://web.archive.org/web/20051103054630/http://www.physics.gla.ac.uk/Optics/projects/ Optical vortices and optical tweezers] at the University of Glasgow
* [http://groups.google.com/group/singular-optics Singular Optics Master list]{{Wayback|url=http://groups.google.com/group/singular-optics |date=20121107020940 }} by Grover Swartzlander Jr., University of Arizona, Tucson
* [https://web.archive.org/web/20051207012119/http://www.aip.org/png/2005/241.htm Optical vortex coronograph], Gregory Foo, et al., University of Arizona, Tucson
* [http://www.physics.nyu.edu/grierlab/hot.html Optical tweezers]{{Wayback|url=http://www.physics.nyu.edu/grierlab/hot.html |date=20160303201649 }}, David Grier, NYU
* [http://wwwrsphysse.anu.edu.au/nonlinear/research/vortex/ Selected Publications on Optical Vortices]{{Wayback|url=http://wwwrsphysse.anu.edu.au/nonlinear/research/vortex/ |date=20070322092433 }} at Australian National University
*{{cite web  | url=http://www.sciam.com/article.cfm?articleID=000F16C0-C84F-1FA2-884F83414B7F0000  | title=All Screwed Up: ''Scientific American'' article  | access-date=2016-04-11  | archive-url=https://web.archive.org/web/20071015191948/http://www.sciam.com/article.cfm?articleID=000F16C0-C84F-1FA2-884F83414B7F0000  | archive-date=2007-10-15  | dead-url=yes  }}
*{{cite web  | url=http://www.newscientist.com/article/dn13522-twisting-light-packs-more-information-into-one-photon.html#.VB7mofl5OCk  | title='Twisting' light packs more information into one photon: New Scientist article  | accessdate=2016-04-11  | archive-date=2015-04-30  | archive-url=https://web.archive.org/web/20150430035106/http://www.newscientist.com/article/dn13522-twisting-light-packs-more-information-into-one-photon.html#.VB7mofl5OCk  | dead-url=no  }}
*{{cite web  | url=http://departments.colgate.edu/physics/research/optics/oamgp/gp.htm  | title=Light Beams in High-Order Modes  | accessdate=2016-04-11  | archive-date=2017-04-17  | archive-url=https://web.archive.org/web/20170417161827/http://departments.colgate.edu/physics/research/optics/oamgp/gp.htm  | dead-url=no  }}
*{{cite web  | url=http://www.unc.edu/~jmspille/187/assign4_forecast.html  | title=Twisted Light Encryption  | deadurl=yes  | archiveurl=https://web.archive.org/web/20070827123346/http://www.unc.edu/~jmspille/187/assign4_forecast.html  | archivedate=2007-08-27  | accessdate=2016-04-11  }}
*{{cite news  | url=http://www.foxnews.com/scitech/2010/01/18/twisted-physics-scientists-create-knots-light/?test=latestnews  | title=Twisted Physics: Scientists Create Knots of Light  | work=Fox News  | date=2010-01-18  | accessdate=2016-04-11  | archive-date=2012-10-24  | archive-url=https://web.archive.org/web/20121024054215/http://www.foxnews.com/scitech/2010/01/18/twisted-physics-scientists-create-knots-light/?test=latestnews  | dead-url=no  }}

[[Category:光學]]