简介：Amultilevelgratingcouplerbasedonsilicon-on-insulator(SOI)materialstructureisproposedtorealizethecouplingbetweenwaveguideandwaveguideorwaveguideandfiber.Thiscoupleriscompatiblewiththecurrentfabricationfacilitiesforcomplementarymetaloxidesemiconductor(CMOS)technologywithverticalcoupling.Thisstructurecanrealizecouplingwhenthebeamswithtransverseelectric(TE)polarizationandtransversemagnetic(TM)polarizationareincidentatthesametime.Theinfluencesofthegratingcouplerparametersincludingwavelength,thethicknessofwaveguidelayer,thethicknessofSiO2layerandthenumberofstepsontheTEmodeandTMmodecouplingefficienciesarediscussed.Theoryresearchesandsimulationresultsindicatethatthewavelengthrangeisfrom1533nmto1580nmwhentheTEmodeandTMmodecouplingefficienciesarebothmorethan40%asthegratingperiodis0.99μm.ThecouplingefficienciesoftheincidentTEandTMmodesare49.9%and49.5%atthewavelengthof1565nm,respectively,andthedifferencebetweenthemisonly0.4%.

简介：Reversibledatahidingtechniquesarecapableofreconstructingtheoriginalcoverimagefromstego-images.Recently,manyresearchershavefocusedonreversibledatahidingtoprotectintellectualpropertyrights.Inthispaper,wecombinereversibledatahidingwiththechaoticHénonmapasanencryptiontechniquetoachieveanacceptablelevelofconfidentialityincloudcomputingenvironments.And,Haardigitalwavelettransformation(HDWT)isalsoappliedtoconvertanimagefromaspatialdomainintoafrequencydomain.Andthenthedecimalofcoefficientsandintegerofhighfrequencybandaremodifiedforhidingsecretbits.Finally,themodifiedcoefficientsareinverselytransformedtostego-images.