{{Short description|Optical device in which light entering any port exits from the next}} {{More citations needed|date=October 2015}}

thumb|Optical Circulator symbol

An '''optical circulator''' is a three- or four-port optical device designed such that light entering any port exits from the next. This means that if light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but instead exits from port 3. This is analogous to the operation of an electronic circulator. Fiber-optic circulators are used to separate optical signals that travel in opposite directions in an optical fiber, for example to achieve bi-directional transmission over a single fiber.<ref>{{cite book|author=IBM Redbooks |date=9 November 1998 |publisher=IBM Corporation|section=5.4.6 Circulators |isbn=0-7384-0058-0 |url=http://imedea.uib-csic.es/~salvador/coms_optiques/addicional/ibm/ch05/05-16.html |title=Understanding Optical Communications |archive-url=https://web.archive.org/web/20150710105519/http://imedea.uib-csic.es/~salvador/coms_optiques/addicional/ibm/ch05/05-16.html |archive-date=2015-07-10 |access-date=10 July 2015}}</ref> Because of their high isolation of the input and reflected optical powers and their low insertion loss, optical circulators are widely used in advanced fiber-optic communications and fiber-optic sensor applications.

Optical circulators are ''non-reciprocal'' optics, which means that changes in the properties of light passing through the device are not reversed when the light passes through in the opposite direction. This can only happen when the symmetry of the system is broken, for example by an external magnetic field. A Faraday rotator is another example of a non-reciprocal optical device, and indeed it is possible to construct an optical circulator based on a Faraday rotator.

==History== In 1965, Ribbens reported an early form of optical circulator that utilized a Nicol prism with a Faraday rotator.<ref name="Ribbens">{{cite journal |last1=Ribbens |first1=William B. |title=An Optical Circulator |journal=Applied Optics |date=1965 |volume=4 |issue=8 |pages=1037–1038 |doi=10.1364/AO.4.001037 |bibcode=1965ApOpt...4.1037R |url=https://opg.optica.org/ao/fulltext.cfm?uri=ao-4-8-1037&id=167852|url-access=subscription }}</ref> With the advent of fiber and guided-wave optics, waveguide-integrable and polarization-independent optical circulators were later introduced.<ref name="Hidetoshi, Hiroshi, et al." >{{cite journal |last1=Hidetoshi |first1=Iwamura |last2=Hiroshi |first2=Iwasaki |last3=Kenichi |first3=Kubodera |last4=Yasuhiro |first4=Torii |last5=Juichi |first5=Noda |title=Simple polarisation-independent optical circulator for optical transmission systems |journal=Electronics Letters |date=1979 |volume=15 |issue=25 |pages=830–831 |doi=10.1049/el:19790590 |bibcode=1979ElL....15..830H |url=https://digital-library.theiet.org/content/journals/10.1049/el_19790590|url-access=subscription }}</ref><ref name="Fuji">{{cite journal |last1=Fuji |first1=Y. |title=High-isolation polarization-independent optical circulator |journal=Journal of Lightwave Technology |date=1991 |volume=9 |issue=10 |pages=1238–1243 |doi=10.1109/50.90921 |bibcode=1991JLwT....9.1238F }}</ref><ref name="Sugimoto, Shintaku, et al.">{{cite journal |last1=Sugimoto |first1=N. |last2=Shintaku |first2=T. |last3=Tate |first3=A. |last4=Terui |first4=H. |last5=Shimokozono |first5=M. |last6=Kubota |first6=E. |last7=Ishii |first7=M. |last8=Inoue |first8=Y. |title=Waveguide polarization-independent optical circulator |journal=IEEE Photonics Technology Letters |date=1999 |volume=11 |issue=3 |pages=355–357 |doi=10.1109/68.748233|bibcode=1999IPTL...11..355S |s2cid=35722016 }}</ref> The concept was later extended to silicon photonic waveguide systems.<ref name="Takei & Mizumoto">{{cite journal |last1=Takei |first1=Ryohei |last2=Mizumoto |first2=Tetsuya |title=Design and Simulation of Silicon Waveguide Optical Circulator Employing Nonreciprocal Phase Shift |journal=Japanese Journal of Applied Physics |date=2010 |volume=49 |issue=52203 |article-number=052203 |doi=10.1143/JJAP.49.052203 |bibcode=2010JaJAP..49e2203T |s2cid=19254463 |url=https://iopscience.iop.org/article/10.1143/JJAP.49.052203/meta|author-link2=Tetsuya Mizumoto|url-access=subscription }}</ref><ref name="Mitsuya, Shoji, et al.">{{cite journal |last1=Mitsuya |first1=Kota |last2=Shoji |first2=Yuya |last3=Mizumoto |first3=Tetsuya |title=Demonstration of a Silicon Waveguide Optical Circulator |journal=IEEE Photonics Technology Letters |date=2013 |volume=25 |issue=8 |pages=721–723 |doi=10.1109/LPT.2013.2247995 |bibcode=2013IPTL...25..721M |s2cid=31886457 |author-link3=Tetsuya Mizumoto}}</ref><ref name="Pintus, Huang, et al.">{{cite journal |last1=Pintus |first1=Paolo |last2=Huang |first2=Duanni |last3=Zhang |first3=Chong |last4=Shoji |first4=Yuya |last5=Mizumoto |first5=Tetsuya |last6=Bowers |first6=John E. |title=Microring-Based Optical Isolator and Circulator with Integrated Electromagnet for Silicon Photonics |journal=Journal of Lightwave Technology |date=2017 |volume=35 |issue=8 |pages=1429–1437 |doi=10.1109/JLT.2016.2644626|bibcode=2017JLwT...35.1429P |s2cid=32824770 |author-link5=Tetsuya Mizumoto|doi-access=free }}</ref><ref name="Huang, Pintus, et al.">{{cite journal |last1=Huang |first1=Duanni |last2=Pintus |first2=Paolo |last3=Zhang |first3=Chong |last4=Morton |first4=Paul |last5=Shoji |first5=Yuya |last6=Mizumoto |first6=Tetsuya |last7=Bowers |first7=John E. |title=Dynamically reconfigurable integrated optical circulators |journal=Optica |date=2017 |volume=4 |issue=1 |pages=23–30 |doi=10.1364/OPTICA.4.000023 |bibcode=2017Optic...4...23H |url=https://opg.optica.org/optica/fulltext.cfm?uri=optica-4-1-23&id=356751|author-link6=Tetsuya Mizumoto|doi-access=free |hdl=11584/463768 |hdl-access=free }}</ref> In 2016, Scheucher et al. have demonstrated a fiber-integrated optical circulator whose nonreciprocal behavior originated from the chiral interaction between a single <sup>85</sup>Rb atom and the confined light in a whispering-gallery mode microresonator. The routing direction of the device is controlled by the internal quantum state of the atom and the device is able to route individual photons.<ref name="Scheucher, Hilico, et al.">{{cite journal |last1=Scheucher |first1=Michael |last2=Hilico |first2=Adèle |last3=Will |first3=Elisa |last4=Volz |first4=Jürgen |last5=Rauschenbeutel |first5=Arno |title=Quantum optical circulator controlled by a single chirally coupled atom |journal=Science |date=2016 |volume=354 |issue= 6319 |pages=1577–1580 |doi=10.1126/science.aaj2118 |pmid=27940579 |arxiv=1609.02492 |bibcode=2016Sci...354.1577S |s2cid=47714 |url=https://www.science.org/doi/abs/10.1126/science.aaj2118}}</ref>

In 2013, Davoyan and Engheta proposed a nanoscale plasmonic Y-circulator based on three dielectric waveguides interconnected with a magneto-optical junction with plasmonic nanorods.<ref name="Davoyan & Engheta">{{cite journal |last1=Davoyan |first1=Arthur R. |last2=Engheta |first2=Nader |author1-link=Nader Engheta |title=Nanoscale plasmonic circulator |journal=New Journal of Physics |date=2013 |volume=15 |issue=83054 |article-number=083054 |doi=10.1088/1367-2630/15/8/083054 |arxiv=1302.5300 |bibcode=2013NJPh...15h3054D |s2cid=119232939 |url=https://iopscience.iop.org/article/10.1088/1367-2630/15/8/083054/meta}}</ref>

==See also== *Optical isolator

==References== {{Reflist}}

==External links== * [http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=1&f=G&l=50&d=PTXT&S1=5909310.PN.&OS=pn/5909310&RS=PN/5909310 US Patent 5,909,310 (USPTO)]{{Dead link|date=August 2025 |bot=InternetArchiveBot |fix-attempted=yes }} [https://patents.google.com/patent/US5909310A/en (Google Patents)]

{{DEFAULTSORT:Optical Circulator}} Category:Optical components