PicoQuant MultiHarp 150 - Introduction

PicoQuantGmbH MultiHarpSoftwareV.3.1.0.0
1. Introduction
Whileintensitybasedfluorescencespectroscopicinvestigationshavebeenfairlycommonforalongtime,ex-
tractingadditionaltemporalinformationfromquantumsystemsviapulsedexcitationandtime-resolveddetection
isarelativelynewandpowerfultechnique.Thetemporalanalysiscanrevealinformationabouttheemitterthat
isnotavailablefromspectraldataalone.Thisiswhytime-resolvedanalysisof(typicallylaserinduced)fluores-
cencebymeansofTime–CorrelatedSinglePhotonCounting(TCSPC)hasgainedinimportanceovertherecent
years.Forinstance,inlifesciencesthedifferenceinthefluorescencedecaytimesoffluorophoresprovidesa
powerfuldiscriminationfeaturetodistinguishmoleculesofinterestfrombackgroundorotherspecies.Thishas
madethetechniqueveryinterestingforsensitiveanalysis,evendowntothesinglemoleculelevel.Thesame
mechanismsareapplicableinquantumoptics,e.g.,whenquantumdotsordefectcentersindiamondareob-
served.
TheacquisitionoffluorescencedecaycurvesbymeansofTCSPCprovidesresolutionandsensitivitythatcan-
notbeachievedwithothermethods.Inpracticeitisdonebyhistogrammingarrivaltimesofindividualphotons
overmanyexcitationandfluorescencecycles.Thearrivaltimesrecordedinthehistogramarerelativetimesbe-
tweenexcitationandcorrespondingfluorescencephotonarrival(start/stoptimes)ideallyresolveddowntoa
fewpicoseconds.Theresultinghistogramrepresentsthefluorescencedecay.Althoughfluorescencelifetime
analysisisagreatfieldofapplicationfortheMultiHarp,itisinnowayrestrictedtothistask.Otherimportantap-
plicationsaree.g.quantumoptics,QuantumCryptography(QC)Time–Of–Flight(TOF)andOpticalTimeDo-
mainReflectometry(OTDR)aswellasanykindofcoincidencecorrelation.
TheMultiHarpisacuttingedgeTCSPCandtimetaggingsystemwithUSBinterface.Itsnewintegrateddesign
providesa flexiblenumber of  inputchannels at  reasonable cost and  allowsinnovativemeasurementap-
proaches.Thetimingcircuitsallowhighmeasurementratesupto78millioncountspersecond(Mcps)each,
withanexcellenttimeresolution
1
andarecordbreakingdeadtimeof650ps.TheUSB3.0
2
superspeedinter-
faceprovidesveryhighthroughputaswellas‘plugandplay’installation.Theinputtriggersareadjustablefora
widerangeofinputsignalsprovidingprogrammableleveltriggersforbothnegativeandpositivegoingsignals.
ThesespecificationsqualifytheMultiHarpforusewithsinglephotondetectorssuchasSinglePhotonAvalanche
Diodes(SPADs),PhotomultiplierTubes(PMT),andsuperconductingnanowiredetectors.Dependingondetec-
torandexcitationsourcethewidthoftheoverallInstrumentResponseFunction(IRF)canbeassmallas100ps
FWHM.TheMultiHarpcanbepurchasedindifferentversionswithupto64timinginputsanonesynchronization
(sync)input.Theuseoftheseinputsisveryflexible.Influorescencelifetimeapplicationsthesyncchannelis
typicallyusedasasynchronizationinputfromalaser.Theotherinputsarethenusedforphotondetectors.In
coincidencecorrelationapplicationsallinputsincludingthesyncinputcanbeusedforphotondetectors.
TheMultiHarpcanoperateinvariousmodestoadapttodifferentmeasurementneeds.Thestandardhistogram
mode performsreal–timehistogramming in on-board memory. Two  differentTime–Tagged–Time–Resolved
(TTTR)modesallowrecordingofeachphotoneventonseparate,independentchannels,therebyprovidingun-
limitedflexibilityinoff–linedataanalysissuchasburstdetectionandtime–gatedorlifetimeweightedFluores-
cenceCorrelationSpectroscopy(FCS)aswellaspicosecondcoincidencecorrelation,usingtheindividualpho-
tonarrivaltimes.TheMultiHarpisfurthermoresupportedbyavarietyofaccessoriessuchaspre–amplifiers,
signaladaptersanddetectorassembliesfromPicoQuant.AsignificantnovelfeatureoftheMultiHarpfamilyis
support  for  White  Rabbit,  allowing  time  transfer  and  synchronization  with  sub-ns  accuracy  (see https://
en.wikipedia.org/wiki/The_White_Rabbit_Project).
TheMultiHarpsoftwarerunsoncurrentWindowsPCplatformsincludingthex64editions.Itprovidesfunctions
forsettingmeasurementparameters,displayingmeasurementresults,loadingandsavingofmeasurementpa-
rametersanddecaycurves.Importantmeasurementcharacteristicssuchascountrate,countmaximumand
position,histogramwidth(FWHM)aredisplayedcontinuously.Datacanconvenientlybeexportedviatheclip-
board,e.g.forimmediateprocessingbytheEasyTau2FluorescenceDecayFitSoftware.Furthermore,apro-
gramminglibrary(DLL)enablesuserstowritecustomdataacquisitionprogramsfortheMultiHarpinvirtuallyall
popularprogrammingenvironments.ThereisalsoalibraryversionforLinux(Intelprocessorarchitectureonly)
whichisfullycompatiblewiththatforWindowssothatapplicationscaneasilybeportedacrossthetwoplat-
forms.
1 Therearebudgetmodelswith80psresolution aswellas highendmodelswith10 and5psresolution.Seethe
appendixofthismanualorwww.picoquant.comfordetailedspecifications.
2 ThelatestUSBspecificationshaveintroducednewnamingschemeswheretheoriginalUSB3.0(5GBits/s)waslater
called“USB3.1Gen1”andnow“USB3.2.Gen1x1”.WesticktotheoriginalnameUSB3.0throughoutthisdocument.
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