简介：Atheoreticalmodelofanonlinearhyperbolicmetamaterialispresentedintheformofastackofsubwavelengthlayersoflinearplasmonicandnonlineardielectricmaterials.Abroadpictureofthepropertiesofevanescentwaves(high-kmodes)inthisstackisinvestigatedbyplottingglobaltransmissiondiagrams.Thepresenceofnonlinearitystronglymodifiesthesediagrams.Theemergenceandmodificationofnonlinearevanescentwavesisobserved.Somesignaturesofnonlinearphenomenonsuchasformationoforbitsandtrajectoriesaroundfixedpointsarealsoseeninourwork.

简介：Themodulationinstabilityofquasi-plane-waveopticalbeamsisinvestigatedintheframeofgeneralizedSchrodingerequationwiththenonlineartermofageneralform.Generalexpressionsarederivedforthedispersionrelation,thecriticaltransversespatialfrequency,aswellastheinstabilitygrowthrate.Theanalysisgeneralizestheknownresultsreportedpreviously.Adetaileddiscussiononthemodulationinstabilityinbiasedcentrosymmetricphotorefractivemediaisalsogiven.

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简介：Theauthorsregretthatoneofthecoauthorswasinadvertentlyomittedinthepreviouspaper[1].E.VarenewasamemberoftheInstitutfrFestkrperphysikattheTechnischeUniversittBerlinandcontributedtotheresultsoncross-phasemodulation.

简介：Basedontheprincipleofspatialpyramidforsignal,amulti-scaletransformoftwo-dimensional(2D)in-terpolatingpyramidisconstructedbythenonlinearmedianoperator.Thetransformpropertiesoferrordiffusehalftoningnoiseonmultiplescalesareinvestigatedandanalyzedthroughexperiments.Accordingtotheseproperties,arobustinversehalftoningmethodisproposed.Thehalftoningimageisfirstlypre-processedbyaGaussianlow-passfilter,anddecomposedbytheone-scaletransform.ThenaWienerfilterisemployedtothedetailedcoefficients.Finallyaninverseimageisreconstructed.Experimentalresultsshowthattheproposedtransformhastheadvantageofseparatingthehalftoningnoiseandimagedetailoverlinearmulti-resolutiontransform.Thepresentedinversehalftoningmethodperformssomeexcellentabilitiesonsharpedge,highpeaksignal-to-noiseratio(PSNR),andsmallmemoryrequirement.

简介：Bythe90°elasticlightscatteringinvestigationandfarfieldobservationintherangeof20-800℃,therelationbetweenbehavioroflightscatteringanomaliesandevolutionofnanodomainstructuresinlatticeofbariumsodiumniobate(Ba_2NaNb_5O_(15),BSN)crystalwasclarified.ThecorrelationbetweenanomaliesonthetemperaturecurvesoftheelasticlightscatteringintensityandtemperaturetransformationsofnanodomainswasstudiedbyX-rayandelectronmicroscopemethods.Phasetransitionnear500℃andmovementinfieldofscatteringlightcouldbeexplainedbyappearanceofanewincommensuratephase.

简介：NonlinearopticalpropertiesofstimulatedBrillouinscattering(SBS)tosignaldetectioninwaterareanalyzed.Withthethresholdcharacteristics,SBSonlyoccurswhenthehighpowerlaserisfocusedintheSBScell.Whenthereisanobjectpresentinfrontofthefocus,itleadstolowerincidentintensityandthenSBSdoesnotoccur.ThebackwardSBSsignaldependsonthefocusinglocation.ThenonlinearopticalpropertiesofSBSprocessinthefocusingregimeareanalyzedtheoretically.Withtheobjectcomingneartothefocusingcenter,thebackwardStokessignalrisesupfromzerotoamaximum,andthengrowstosaturation.Thedelaytimeoftheechosignaltopumpsignalcangivetheobjectlocation.Inexperiment,thepeakpositionofvaryingrateofenergycangiveobjectlocation.

简介：Backconversionisanintrinsicphenomenoninnonlinearfrequencydown-conversionprocesses.However,thephysicalreasonforitsoccurrenceisnotwellunderstood.Here,wetheoreticallyrevealthatbackconversionistheresultofaπ-phasejumpassociatedwiththedepletionofoneinteractingwave.Bysuppressingtheidlerphasejumpthroughadeliberatecrystalabsorption,thebackconversioncanbeinhabited,thusenhancingtheconversionefficiencyfromthepumptothesignal.TheresultspresentedinthisLetterwillfurthertheunderstandingofnonlinearparametricprocessesandpavethewaytowardthedesignofhighlyefficientdown-conversionsystems.

简介：Thenonlinearswitchingcharacteristicsoffusedfiberdirectionalcouplerswerestudiedexperimentally.Byusingfemtosecondlaserpulseswithpulsewidthof100fsandwavelengthofabout1550nmfromasystemofTi:sapphirelaserandopticalparametricamplifier(OPA),thenonlinearswitchingpropertiesofanullcoupleranda100%couplerweremeasured.Theexperimentalresultswerecoincidentwiththesimulationsbasedonnonlinearpropagationequationsinfiberbyusingsuper-modetheory.Nonlinearlossinfiberwasalsomeasuredtogettheinjectedpoweratthecoupler.Afterdeductingthenonlinearlossandinputefficiency,thenonlinearswitchingcriticalpeakpowersfora100%andanullfusedcouplerswerecalculatedtobe9410and9440W,respectively.ThenonlinearlossparameterPNinanexpressionofαNL=αP/PNwasobtainedtobePN=0.23W.

简介：Weproposeajointnonlinearelectricalequalizationapproachincoherentopticaldiscrete-Fourier-transformspreadorthogonal-frequency-division-multiplexing(DFT-spread-OFDM)systemswithpolarizationdivisionmultiplexing(PDM).ThismethodisbasedonanadaptiveVolterraseriesexpansionfornonlineardistortionsoftwoorthogonalpolarizations.Thenonlinearelectricalequalizationisvalidatedthroughnumericalsimulationof100-Gb/squadraturephaseshiftkeyingand200-Gb/s16quadratureamplitudemodulationPDMDFT-spread-OFDMsystems.

简介：Amaster-slaveconfigurationusedtocontrolthenonlinearbehaviorsarisinginaverticalcavitysurfaceemittinglaser(VCSEL)withstrongexternalopticalfeedbackisestablished.Intermsofbifurcationdiagram,timeandfrequencydomain,theinfluenceofthecontinuousopticalinjectionfromthemasterVCSELonthenonlinearcharacteristicsoftheslaveisinvestigatedtheoretically.Forrelativelyweakinjection,theslavestillkeepsitsintrinsicnonlinearstate.Withincreasingtheinjectionstrength,thesenonlinearbehaviorsevolvetoperiodicfluctuation,andatlastarereplacedbythesteady-state(e.g.thecriticalinjectionparameterforsteady-stateis1.2whenexternalcavity'sreflectivityandlengthare4%and4cm,respectively).Duringthisevolutionthebifurcation-contractionphenomenaarealsoobserved.

简介：Thenonlineareffectsthatlimittheperformanceofthemulti-frequencyprobe(MFP)basedcoherentopticaltimedomainreflectometry(C-OTDR)areinvestigated.Basedontheoreticalanalysisandexperimentalresults,comparedwithconventionalC-OTDR,whentheprobepulsehaspowergradientwithinthepulsewidth,self-phasemodulation(SPM)andcross-phasemodulation(XPM)arestrengthenedinthenewC-OTDRscheme.Thegenerationoffour-wavemixing(FWM)isdependentonSPMandXPM,andwithmodulationfrequencyofphasemodulatorhigherthan40MHz,thestimulatedBrillouinscattering(SBS)thresholdcanbeenhancedbymorethan5dB,whichbenefitsthemaximumdynamicrangeoftheMFPC-OTDR.

简介：Non-uniformstep-sizedistributionisimplementedforsplit-stepbasednonlinearcompensationinsingle-channel112-Gb/s16quadratureamplitudemodulation(QAM)transmission.Numericalsimulationsofthesystemincludinga20×80kmuncompensatedlinkareperformedusinglogarithmicstepsizedistributiontocompensatesignaldistortions.50%ofreductioninnumberofstepswithrespecttousingconstantstepsizesisobserved.Theperformanceisfurtherimprovedbyoptimizingnonlinearcalculatingposition(NLCP)incaseofusingconstantstepsizeswhileNLCPoptimizationbecomesunnecessarywhenusinglogarithmicstepsizes,whichreducesthecomputationaleffortduetouniformlydistributednonlinearphaseforallsuccessivesteps.