声子晶体缺陷态的温度控制及兰姆波禁带的低频调节开题报告

声子晶体缺陷态的温度控制及兰姆波禁带的低频调节开题报告Title:TemperatureControlofDefectStatesinPhononicCrystalsandLow-frequencyTuningofLamb-waveBandgapIntroduction:Phononiccrystalsareperiodicstructuresthatcanmanipulatesoundwavesinamannersimilartothewayphotoniccrystalsmanipulatelightwaves.Theycanbeengineeredtohavebandgapswherecertainfrequenciesofsoundwavescannotpropagate,makingthemusefulforacousticwavefiltering,isolation,andsensingapplications.However,phononiccrystalsarealsopronetodefectsthatcandegradetheirperformance.Defectscanarisefromstructuraldisorder,substrateinteractions,orfabricationimperfections,andtheycancreatelocalizedstateswithinthebandgapthatcantrapandscattersoundwaves.Thegoalofthisprojectistoinvestigatemethodsfortemperaturecontrolofdefectstatesinphononiccrystalsandlow-frequencytuningofLamb-wavebandgap.Temperaturecontrolcanbeusedtoinduceandsuppressdefectstates,whichcanhelptooptimizephononiccrystalperformance.Low-frequencytuningcanbeusedtoshifttheLamb-wavebandgaptolowerfrequencies,wheremanybiologicalandenvironmentalsignalsarefound,makingphononiccrystalspotentiallyusefulforbiosensingandenvironmentalmonitoringapplications.Objectives:1.Fabricateandcharacterizephononiccrystalsamplesusingstandardmicrofabricationtechniquesandopticalmicroscopy.2.Measureandmodelthephononiccrystaltransmissionspectraasafunctionoftemperatureusingatemperature-controlledsampleholderandalaservibrometertoexciteanddetectacousticwaves.3.Identifydefectstateswithinthephononiccrystalbandgapusingnumericalsimulationsandcomparewithexperimentalobservations.4.Controlthepopulationandamplitudeofdefectstatesusingtemperatureandthermalannealing,andmeasuretheresultingchangesinphononiccrystalperformance.5.DesignandfabricatephononiccrystalswithtailoredLamb-wavebandgapsusingnumericalsimulationsandmicrofabricationtechniques.6.MeasureandmodeltheshiftingoftheLamb-wavebandgapasafunctionofthestructuralandmaterialparametersofthephononiccrystal,andcomparewiththeoreticalpredictions.7.Demonstratelow-frequencytuningoftheLamb-wavebandgapbydesigningandfabricatingdeviceswithdifferentstructuralandmaterialconfigurations.Methods:Theprojectwillstartbyfabricatingandcharacterizingphononiccrystalsamplesusingstandardmicrofabricationtechniquesandopticalmicroscopy.Thesampledesignwillconsistofasquarelatticeofcylindricalholesinasiliconsubstrate.Theholediameterandspacingwillbevariedtocreateabandgapcenteredaround1MHzforLambwaves.Transmissionspectrawillbemeasuredusingalaservibrometertoexciteanddetectacousticwaves,whileatemperature-controlledsampleholderwillallowmeasurementstobetakenasafunctionoftemperature.Themeasuredtransmissionspectrawillbecomparedwithnumericalsimulationsusingfiniteelementanalysissoftwaretoidentifythelocationandamplitudeofdefectstateswithinthebandgap.Defectstateswillbecontrolledusingtemperatureandthermalannealing,andchangesinphononiccrystalperformancewillbemeasured.PhononiccrystalswithtailoredLamb-wavebandgapswillbedesignedandfabricatedusingnumericalsimulationsandmicrofabricationtechniques.Thebandgapwillbeshiftedtolowerfrequenciesbychangingtheholediameter,spacing,andsubstratematerial.TheshiftingoftheLamb-wavebandgapwillbemeasuredandmodeledusingthesametechniquesasbefore.Finally,low-frequencytuningoftheLamb-wavebandgapwillbedemonstratedbydesigningandfabricatingdeviceswithdifferentstructuralandmaterialconfigurations.ExpectedResults:Theprojectisexpectedtoyieldnewinsightsintothetemperaturecontrolofdefectstatesinphononiccrystalsandlow-frequencytuningofLamb-wavebandgap.Theresultswillhaveapplicationsinbiosensing,environmentalmonitoring,andacousticwaveisolationandfiltering.Specificexpectedresultsincludetheoptimizationofphononiccrystalperformancethroughdefectstatecontrol,thedesignofphononiccrystalswithtailoredLamb-wavebandgaps,andthedemonstrationoflow-frequencytuningoftheLamb-wavebandgap.Conclusion:Phononiccrystalsarepromisingmaterialsforacousticwavemanipulation,butdefectscanlimittheirperformance.Bycontrollingthetemperatureofphononiccrystalsamples,defectstatescanbeinducedandsuppressed,leadingtooptimizedperformance.Furthermore,bytailoringthestructuralandmaterialparametersofphononiccrystals,theirLamb-wavebandgapcanbeshift