Table Of ContentSaroj Rout · Sameer Sonkusale
Active
Metamaterials
Terahertz Modulators and Detectors
Active Metamaterials
Saroj Rout • Sameer Sonkusale
Active Metamaterials
Terahertz Modulators and Detectors
123
SarojRout SameerSonkusale
MixignalInnovations ElectricalandComputerEngineering
Nashua,NH,USA TuftsUniversity
Medford,MA,USA
ISBN978-3-319-52218-0 ISBN978-3-319-52219-7 (eBook)
DOI10.1007/978-3-319-52219-7
LibraryofCongressControlNumber:2017930655
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To ourparents
Preface
Metamaterials,firstknownasleft-handedmaterials(LHMs)ornegative-indexmate-
rials(NIMs),areartificiallyconstructedeffectivematerialsusingperiodicstructures
thatareafractionofthewavelengthoftheincidentelectromagneticwave,resulting
in effective electric and magnetic properties (permittivity and permeability) that
are unavailable in natural materials. The ability to design effective materials with
deterministic electromagnetic properties makes them very attractive for terahertz
applicationssincenaturalmaterialsdonotrespondwelltothisfrequencyregime.
Since the discovery and experimental demonstration of artificial material with
negative permittivity and negative permeability by Sir Pendry et al. in 1996
and 1999, the research interest in metamaterials has significantly increased. In
spite of the intense research activities in the last two decades, application of
metamaterials to terahertz frequencies is a recent phenomenon. And, terahertz
metamaterials embedded with active devices are even a smaller portion of this
researchlandscape.Moreover,thetransitionfromresearchtoreal-worldapplication
ofterahertzmetamaterialsisstillyearsbehindbecauseofnumerousimplementation
challenges.
This book intends to close that gap by providing theoretical background and
experimentalandfabricationmethodsinonecomprehensivetext.Thisiswellsuited
forengineersandphysiciststobeabletodesign,fabricate,andcharacterizeterahertz
metamaterialdevicesincommercialplanarsemiconductorprocesses.
Three case studies are covered in detail involving terahertz modulator and
detectorimplementedincommercialgalliumarsenide(GaAs)andcomplementary
metal-oxidesemiconductor(CMOS)processforimagingandcommunicationappli-
cations.
Thefirstthreechaptersprovidetheintroduction,backgroundtheory,andexper-
imental methods which give the reader the motivation and basic background to
understandterahertz metamaterials. The last three chapters provide the three case
studies of active metamaterials fabricated in planar semiconductor process for
terahertzimagingandcommunicationapplications.
Chapter 1 begins by providing the motivation for working in the terahertz
frequency regime for its numerous important applications and showing, with
vii
viii Preface
quantitativereasoning,whymetamaterialsareasuitabletechnologyforthatregime.
An overviewof technologiesfor terahertzwave modulatorsis presented,which is
theprimarystructureunderlyingallofthedesignsinthistext.
Chapter 2 reviews some of the basic electromagnetic principles for a basic
understanding of metamaterials. One of the key contributions of this text is the
analysisofterahertzwavemodulatorsusingtheDrude–Lorentzmodel.
Chapter3coverstheexperimentalmethodsformodeling,simulating,andchar-
acterizing terahertz metamaterials. A section on CMOS fabrication is introduced
withfewmetamaterialcasestudiesforreaderstogetfamiliarwithaveryaccessible
process that can be used for limited terahertz metamaterial applications. For
metamaterialcharacterization,terahertztime-domainspectroscopy(THz-TDS)and
continuous-waveterahertzspectroscopy(cw-THz)arecoveredindetail.Asectionis
alsodedicatedtothealignmentofoff-axisparabolicmirrors,whichisfoundinmost
terahertztestsetupsandshouldbeavaluableresourceforanyonedoingexperiments
inthisfield.
Chapter 4 coversa case study ofmetamaterial-basedterahertzmodulatorusing
embeddedHEMT devices which is one of the main contributionsto the scientific
literature by the authors. Design principle of HEMT-controlled metamaterial is
coveredin detail based on the modulatorprinciple introducedin Chap.2. Design,
fabrication,experimentalsetup,andtestresultsarealsocoveredinthischapter.
Chapter 5 covers another case study of an all solid-state metamaterial-based
terahertzspatiallightmodulator(SLM)usingtheHEMT-basedmodulatordescribed
in Chap.4. The principle behind single-pixel imaging is presented in this chapter
followedbydesign,fabrication,andtestoftheSLM.
Chapter6presentsthelastcasestudyofaterahertzfocalplanearray(FPA)using
metamaterials in a 0.18(cid:2)m CMOS process. The principle of resistive self-fixing
detectioniscoveredfollowedbythedesignandsimulationoftheFPA.
Nashua,NH,USA SarojRout
Medford,MA,USA SameerSonkusale
Acknowledgments
Therehavebeenquiteafewwhohaveinspiredandmotivatedthisworkandhelped
us design, simulate, and characterize. We want to begin by thanking Dr. Willie
Padilla whose department colloquiums at Tufts University were to sow the seeds
forthecontributionswemadeinthistext.Wewanttothankhimforintroducingus
tothisexcitingfieldofmetamaterials.We alsowanttothankhisdoctoralstudents
Dr.DavidShrekenhamerandChrisBinghamforhelpwiththedesignandsimulation
ofthemodulators.Davidinparticularspentcountlesshourshelpingussimulateand
testtheHEMT-basedmetamaterialmodulatorwedeveloped.Wealsowanttothank
Dr. RichardAverittandDr. AndrewStrikwerdaforhelpinguswith their terahertz
time-domainspectroscopy(THz-TDS)setupforcharacterizingthemodulator.
We thank Dr. Wangren Xu for contributing Sect.3.2 on design for fabrication
in foundry process. Our thanks to Jessie Tovera for assembly of the spatial light
modulator(SLM).
OurspecialthankstoMr.CharlesB.Glaser,editorialdirectoratSpringerUSA,
forencouraginguswithwritingtheproposalofthisbookandprovidingusfeedback
andclarificationthroughoutthewritingprocess.
We acknowledge the support of the Office of Naval Research under US Navy
Contracts N00014-07-1-0819 and N00014-09-1-1075, and the National Science
FoundationAwardsNo.ECCS-1002340andECCS-1002152.
We also acknowledgethe supportof DoD Defense UniversityResearch Infras-
tructure Program (DURIP) under grant N00014-12-1-0888 equipment purchase
usedfortestandcharacterization.
Finally, we want to thank our familiesfor their unconditionalloveand support
withoutwhichnothingwouldeverbepossible.
ix
Contents
1 Introduction .................................................................. 1
1.1 TowardsClosingthe“TerahertzGap”................................. 1
1.1.1 WhyIsthe“TerahertzGap”Interesting....................... 3
1.1.2 ABriefHistoryofTerahertzTechnologies ................... 6
1.2 IntroductiontoMetamaterials ......................................... 8
1.2.1 ABriefHistory................................................. 8
1.2.2 OverviewofMetamaterials.................................... 9
1.2.3 Metamaterials:A Suitable Technologyfor
TerahertzDevices .............................................. 14
1.3 OverviewofTerahertzWaveModulators ............................. 16
References..................................................................... 21
2 BackgroundTheory ......................................................... 27
2.1 PlaneWavesinaNonconductingMedium............................ 27
2.1.1 NegativeRefractiveIndex ..................................... 30
2.1.2 PropagationofWavesinLeft-HandedMaterial.............. 30
2.1.3 PropagationofWavesinSingleNegativeMedium........... 31
2.2 DispersioninNonconductors.......................................... 31
2.2.1 LorentzOscillatorModelforPermitivity..................... 32
2.2.2 AnomalousDispersionandResonantAbsorption............ 33
2.3 MetamaterialasaModulator .......................................... 36
References..................................................................... 38
3 ExperimentalMethods ...................................................... 41
3.1 ElectromagneticModelingandSimulationsofMetamaterials....... 41
3.1.1 BoundaryandSymmetryConditions ......................... 42
3.1.2 HomogenousParameterExtraction ........................... 43
3.2 DesignforFabricationinFoundryProcesses......................... 43
3.2.1 Typical45nmCMOSProcess ................................. 44
3.2.2 PhysicalPropertiesofMetalandDielectricsat
OpticalFrequencies............................................ 45
3.2.3 CaseStudies.................................................... 46
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xii Contents
3.3 TestandCharacterization .............................................. 50
3.3.1 TerahertzTime-DomainSpectroscopy(THz-TDS) .......... 50
3.3.2 Continuous-Wave(cw)TerahertzSpectroscopy.............. 56
3.3.3 OpticalAlignmentofOff-AxisParabolicMirrors............ 60
References..................................................................... 64
4 High-SpeedTerahertzModulationUsingActiveMetamaterial........ 67
4.1 Introduction............................................................. 67
4.2 DesignPrincipleoftheHEMTControlledMetamaterial
Modulator............................................................... 68
4.2.1 CircuitModelfortheElectric-CoupledLC
(ELC)Resonator............................................... 69
4.2.2 PrincipleofVoltageControlledTerahertzWave
Modulator....................................................... 71
4.3 DesignandFabrication................................................. 73
4.4 ExperimentalSetup..................................................... 75
4.5 ResultsandDiscussion................................................. 77
4.5.1 THzTransmissionwithDC-BiasedHEMT................... 77
4.5.2 ComputationalInvestigation................................... 78
4.5.3 HighFrequencyTHzModulation............................. 79
References..................................................................... 81
5 ATerahertzSpatialLightModulatorforImagingApplication ........ 83
5.1 IntroductiontoSingle-PixelImaging.................................. 83
5.1.1 ABriefHistoricalPerspective................................. 85
5.1.2 ImagingTheory ................................................ 86
5.2 AReviewofTHzSpatialLightModulators .......................... 87
5.3 SpatialLightModulatorDesignandAssembly....................... 90
5.4 CircuitDesignforElectronicControloftheSLM.................... 95
5.5 ExperimentalSetupforTerahertzCharacterizationandImaging.... 96
5.6 ResultsandDiscussions................................................ 97
5.6.1 TerahertzCharacterizationoftheSpatialLight
Modulator....................................................... 97
5.6.2 Single-PixelTerahertzImaging................................ 98
References..................................................................... 100
6 ATerahertzFocalPlaneArrayUsingMetamaterialsina
CMOSProcess ............................................................... 103
6.1 Introduction............................................................. 103
6.2 A0.18(cid:2)mCMOSFoundryProcessTechnology..................... 104
6.3 PrincipleofResistiveSelf-MixingDetection......................... 106
6.4 MetamaterialBasedTerahertzCMOSDetectorDesign.............. 108
6.4.1 Terahertz Detection Using Source-Driven
Self-MixingArchitecture...................................... 108
6.4.2 CircuitArchitectureforTerahertzDetection ................. 109
6.5 MetamaterialDesignforTerahertzDetection......................... 109
