Optical parametric oscillator: Difference between revisions

Revision as of 22:23, 2 October 2016

Revision as of 14:37, 4 December 2016

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An important feature of the OPO is the coherence and the spectral width of the generated radiation.

When the pump power is significantly above threshold, the two output waves are, to a very good approximation, [[coherent state]]s (laser-like waves). The linewidth of the resonated wave is very narrow (as low as several kHz). The nonresonated generated wave also exhibits narrow linewidth if a pump wave of narrow linewidth is employed. Narrow-linewidth OPOs are widely used in spectroscopy.<ref name = BJO>{{cite book |editor =[[F. J. Duarte|Duarte FJ]] |title=Tunable Laser Applications | edition = 3rd |publisher= [[CRC Press]] |___location=Boca Raton |year=2016 |isbn=9781482261066 |oclc= |doi= |accessdate= | authorvauthors = [[Brian Orr|Orr BJ]];, Haub J G; He Y;JG, White RT | chapter = Spectroscopic Applications of Pulsed Tunable Optical Parametric Oscillators | pages = 17–142 }}</ref>

==Quantum properties of the generated light beams==

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It turns out that the phases of the twin beams are quantum correlated as well, leading to [[Quantum entanglement|entanglement]], theoretically predicted in 1988.<ref>{{cite journal|author1=M. D. Reid |author2=P. D. Drummond |lastauthoramp=yes |journal=Phys. Rev. Lett. |volume=60|page=2731|doi=10.1103/PhysRevLett.60.2731 |year=1988|title=Quantum Correlations of Phase in Nondegenerate Parametric Oscillation|issue=26|bibcode=1988PhRvL..60.2731R}}</ref> Below threshold, entanglement was measured for the first time in 1992,<ref>{{cite journal|author1=Z. Y. Ou |author2=S. F. Pereira |author3=H. J. Kimble |author4=K. C. Peng |last-author-amp=yes |journal=Phys. Rev. Lett. |volume=68|page=3663|doi=10.1103/PhysRevLett.68.3663 |year=1992|title=Realization of the Einstein-Podolsky-Rosen paradox for continuous variables|issue=25|bibcode=1992PhRvL..68.3663O}}</ref> and in 2005 above threshold.<ref>{{cite journal|author1=A. S. Villar |author2=L. S. Cruz |author3=K. N. Cassemiro |author4=M. Martinelli |author5=P. Nussenzveig |last-author-amp=yes |journal=Phys. Rev. Lett. |volume=95|page=243603|doi=10.1103/PhysRevLett.95.243603 |year=2005|title=Generation of Bright Two-Color Continuous Variable Entanglement|issue=24|bibcode=2005PhRvL..95x3603V|arxiv = quant-ph/0506139 }}</ref>

Above threshold, the pump beam depletion makes it sensitive to the quantum phenomena happening inside the crystal. The first measurement of squeezing in the pump field after parametric interaction was done in 1997.<ref name="KasaiJiangrui1997">{{cite journal|author1last1=K. Kasai |author2first1=K|last2=Jiangrui|first2=J.G. Gao |author3last3=Fabre|first3=C.|title=Observation Fabreof squeezing |last-author-amp=yesusing cascaded nonlinearity|journal=Europhysics Europhys.Letters Lett.(EPL)|volume=40|pageissue=25 1|year=1997|bibcode pages= 1997EL.....40...25K 25–30|issn=0295-5075|doi = 10.1209/epl/i1997-00418-8 }}</ref>
It has been recently predicted that all three fields (pump, signal and idler) must be entangled,<ref>{{cite journal|author1=A. S. Villar |author2=M. Martinelli |author3=C Fabre |author4=P. Nussenzveig |last-author-amp=yes |journal=Phys. Rev. Lett. |volume=97|page=140504|doi=10.1103/PhysRevLett.97.140504 |year=2006|title=Direct Production of Tripartite Pump-Signal-Idler Entanglement in the Above-Threshold Optical Parametric Oscillator|issue=14|bibcode=2006PhRvL..97n0504V|arxiv = quant-ph/0610062 }}</ref> a prediction which was experimentally demonstrated by the same group.<ref>{{cite journal | last1 = Coelho | first1 = A. S. | last2 = Barbosa | first2 = F. A. S. | last3 = Cassemiro | first3 = K. N. | last4 = Villar | first4 = A. S. | last5 = Martinelli | first5 = M. | last6 = Nussenzveig | first6 = P. | year = 2009 | title = Three-Color Entanglement | url = http://www.sciencemag.org/content/326/5954/823.abstract | journal = Science | volume = 326 | issue = 5954| pages = 823–826 | doi=10.1126/science.1178683|arxiv = 1009.4250 |bibcode = 2009Sci...326..823C }}</ref>

Not only intensity and phase of the twin beams share quantum correlations, but also do their spatial modes.<ref>{{cite journal|author1=M. Martinelli |author2=N. Treps |author3=S. Ducci |author4=S. Gigan |author5=A. Maître |author6=C. Fabre |last-author-amp=yes |journal=Phys. Rev. A |volume=67|page=023808|doi=10.1103/PhysRevA.67.023808 |year=2003|title=Experimental study of the spatial distribution of quantum correlations in a confocal optical parametric oscillator|issue=2|arxiv = quant-ph/0210023 |bibcode = 2003PhRvA..67b3808M }}</ref> This feature could be used to enhance signal to noise ratio in image systems and hence surpass the standard quantum limit (or the shot noise limit) for imaging.<ref>{{cite journal | last1 = Treps | first1 = N. | last2 = Andersen | first2 = U. | last3 = Buchler | first3 = B. | last4 = Lam | first4 = P. K. | last5 = Maitre | first5 = A. | last6 = Bachor | first6 = H.-A. | last7 = Fabre | first7 = C. | year = 2002 | title = Surpassing the Standard Quantum Limit for Optical Imaging Using Nonclassical Multimode Light | url = | journal = Phys. Rev. Lett | volume = 88 | issue = 20| page = 203601 | doi = 10.1103/PhysRevLett.88.203601 | bibcode=2002PhRvL..88t3601T|arxiv = quant-ph/0204017 }}</ref>