简介：Photoconductiveswitcheswerethekeycomponentsthatallowedthegenerationanddetectionofcoherentbroadbandelectromagneticpulsesatterahertzfrequencies,openingthepossibilityforperformingspectroscopyand,therefore,measuringcomplexdielectricpropertiesofmaterialsinthisband,whichwasmostlyunexplored.Inthispaper,wepresentabriefintroductiontotheoperationprinciplesofthesedevices.Subsequently,wepresentareviewofthecurrentstate-of-the-artinthisfieldanddiscussthechallengestobefacedinfuturedevelopmentofthesedevices.

简介：Microplasmasareveryinterestingduetotheiruniquepropertiesandachievableregimesmaintainedatatmosphericpressures.Duetothesmallscales,numericalmodelingcouldcontributetotheunderstandingofunderlyingphenomenaasitprovidesaccesstolocalparameters—andcomplementsexperimentalglobalcharacteristics.Aself-consistentformalism,appliedtonanosecondpulsedatmosphericnon-equilibriumheliumplasmas,revealsthatseveralsuccessivedischargescanpersistasaresultofacombinedvolumeanddielectricsurfaceeffects.Thevaluableinsightsprovidedbythespatiotemporalsimulationresultsshowthecriticalimportanceofcoupledgasandplasmadynamics—namelygasheatingandelectricfieldreversals.

简介：Laserdriversareanenablingfactortoinertialconfinementfusion,becauselaserdiodesmustbeusedinsteadofflashlamps.Wediscussthelimitationsoflaserdiodearraysandshowwhatstepstheindustryistaking.Thepumppowerrequirementsoflarge-scaleprojectssuchasLIFEorHiPERarewithinreachofsemiconductorlaserdiodeassemblies.Pulsedlightoutputpowersperlaserbarshavebeenaround300Wperbar,asintheJenoptik940nmbarspreviouslyusedforpumpingtheYb:YAGslabsintheDiPOLEproject.Byredesigningthesemiconductorlaserstructures500Wperbarisnowcommerciallyavailablefor808,880and940nmpumpwavelengths.Theconstructionofoneinertialfusionpowerplantwillrequireanamountofsemiconductorlaserchipsinexcessofthecurrentannualproductionbytwoordersofmagnitude.Thisaddstotheengineeringtaskofimprovingthedevicecharacteristicsachallengetoproductioncapacity.Whiletheindustrybenefitsfromtherecentboostinsolid-statelightingthatactsasatechnologydriver,cooperationbetweenmanufacturerswillbeimperative,andtothisendweproposestandardizationefforts.

简介：Atypeofnovelinverterpowersupplysystemforhigh-powertwin-wirepulsedgasmetalarcwelding(GMAW)ispresentedmainlyfordealingwiththedisadvantagesoftheconventionalpowersupplyfortwin-wirepulsedGMAWofwhichtheoutputpowerisgenerallydifficulttoincreaseduetolimitationsofthepowerofsemiconductorsandthepowerdensityofmagneticdevices.Inthepowersuppliesforthemasterandslavearcs,thedigitalsignalprocessor(DSP)TMS320F28335isusedtoformtheDSP-basedsynergiccontrolsystemforparallelhigh-powerpulsedGMAW,whichachieveshigh-poweroutputoftwoparallelinverterscontrolledbyasingleDSP;master-slavecommunicationisachievedbyusingecontrollerareanetwork(eCAN)moduleofDSP,thusrealizinganti-phasepulseoutputofhigh-powertwin-wirepulsedGMAWandreducingtheinterferencebetweentwinarcs.Theexperimentresultsdemonstratethatthedesignedinverterpowersupplysystemforhigh-powertwin-wirepulsedGMAWcanbringabouthigh-powerefficiencyofwelding,stableweldingprocessandproperformationofwelds.

简介：Bariumferrite（BaM）thinfilmsaredepositedonplatinumcoatedsiliconwafersbypulsedlaserdeposition（PLD）.Theeffectsofdepositionsubstratetemperatureonthemicrostructure,magneticandmicrowavepropertiesofBaMthinfilmsareinvestigatedindetail.Itisfoundthatmicrostructure,magneticandmicrowavepropertiesofBaMthinfilmareverysensitivetodepositionsubstratetemperature,andexcellentBaMthinfilmisobtainedwhendepositiontemperatureis910℃andoxygenpressureis300mTorr（1Torr=1.3332×102Pa）.X-raydiffractionpatternsandatomicforcemicroscopyimagesshowthatthebestthinfilmhasperpendicularorientationandhexagonalmorphology,andthecrystallographicalignmentdegreecanbecalculatedtobe0.94.Hysteresisloopsrevealthatthesquarenessratio（Mr/Ms）isashighas0.93,thesaturatedmagnetizationis4004Gs（1Gs=104T）,andtheanisotropyfieldis16.5kOe(1Oe=79.5775A·m-1).Ferromagneticresonancemeasurementsrevealthatthegyromagneticratiois2.8GHz/kOe,andtheferromagneticresonancelinewithis108Oeat50GHz,whichmeansthatthisthinfilmhaslowmicrowaveloss.ThesepropertiesmaketheBaMthinfilmshavepotentialapplicationsinmicrowavedevices.

简介：Differentialabsorptionlidar(DIAL)isanexcellenttechnologyforatmosphericCO2detection.However,theaccuracyandstabilityofatransmittedon-linewavelengtharestrictlyrequiredinaDIALsystem.Thefluctuationofatunablepulsedlasersystemisrelativelymoreseriousthanthatofotherlasersources,andthisconditionleadstoalargemeasurementerrorforthelidarsignal.Theseconcernsposeasignificantchallengeinon-linewavelengthcalibration.Thisstudyproposesanalternativemethodbasedonwaveletmodulusmaximafortheaccurateon-linewavelengthcalibrationofapulsedlaser.Becauseofthedifferentpropagationcharacteristicsofthewavelettransformmodulusmaximabetweensignalandnoise,thesingularitiesofasignalcanbeobtainedbydetectionofthelocalmodulusmaximainthewavelettransformmaximumatfinescales.Simulatedanalysisshowsthatthemethodismoreaccuratethanthegeneralmethodsuchasquinticpolynomialfittingandcansteadilymaintainhighcalibrationprecisionatdifferentsignal-to-noiseratios(SNRs).Last,16groupsofrealexperimentswereconductedtoverifythesimulatedanalysis,whichshowsthattheproposedmethodisanalternativeforaccuratelycalibratinganon-linewavelength.Inaddition,theproposedmethodisabletosuppressnoisesintheprocessofwavelengthcalibration,whichgivesitanadvantageinaccurateon-linewavelengthcalibrationwithalowSNR.

简介：ThestimulatedBrillouinscattering(SBS)thresholdaffectedbyrepetitionrateandpulsedurationinasinglefrequencynanosecondpulsedfiberamplifierisstudied.TheexperimentalresultsdemonstratethattheSBSthresholdcanbeimprovedeitherbyreducingtherepetitionrateorbynarrowingthepulseduration;however,theaveragepowermaybelimitedinsomecases.Otherwise,twoevaluationmethodsfortheSBSthresholdinthefiberamplifierarecomparedanddiscussed,aimingtoobtainamoreaccuratedescriptionfortheSBSthresholdinoursingle-frequencyamplifiersystem.