1、Lecture 1: Guiding Light Along Nanoparticle Arays5 nmLecture 1: Guiding Light AlongNanoparticle AraysEHWhat hapened at the last LectureCoupling light to surface plasmon-polaritons Kretchman geometry Grating coupling/,Airspm=kG2/,siSiOdspkkc!“#= Coupling from a metal dotGuiding geometries Stripes and
2、 wires Line defects in hexagonal arrays (2d photonic crystals) Today: nanoparticle arraysWhat hapened at the last LectureS.A. Maier, M.L. Brongersma H.A. Atwater, Apl. Phys. Let. 78, 16, 201 Light and microwaves are electromagnetic waves described by Maxwells equations SEM of array of 50 nm Au parti
3、cles = 60 nm, = 3.1x1015rad/sd = 75 nm Near field optical excitation60 nmGuiding of light along an aray of Au nanoparticles ?Guiding of light along an aray of Aunanoparticles ?A cm-scale Analogue to a Plasmonic Device8 GHz = 3.7 cmd = 2 mh = 1.4 cm101 Cu rodsExperimental setup 90% of the energy is c
4、onfined within a distance of 0.05F 3-4 dB los at a corner due far-field radiation-1012345-2-10123x (wavelngths)y(wavelngths)sourceI/I0(dB)x (wavelengths)01 2 3 -1 -2 - X Y Plot of |Ez| on a logarithmic scale-1-20-0-00-10Stefan A. Maier et al.,Appl. Phys. Lett. 78, 16, 2001A cm-scale Analogue to aPla
5、smonic Device Light can penetrate metallic nanoparticles and set the electrons in motion This collective electron motion is called a plasmon50 nanometer Au, Ag, or Cu particleE field+-+-+-+-+-+-+-+-+-+-+-Mode size 64 % for all possible corner and T structures Calculations easily extended to 3D struc
6、turesPower Transmision Coeficients, T AFM manipulation of 30 nm Au particles on APTS coated SiO2(APTS = AminoPropylTrimethoxySilane) Advantages: Au particles and chemicals comercialy available.Flexibility to image and modify structures.Fabrication of Arrays by AFM ManipulationSheffer Meltzer, Aristi
7、des A.G.Requicha, and Bruce E. Koel, USC1 mFabrication of Arays by AFMManipulationThe Role of Defects and Disorder ReflectionsPeriodicityDipole approximation: T= 1 9(d/d)2Example: d/d = 5% (5nm/75nm) T= 96 %Size fluctuationsDipole approximation:Example: V/V = 9% (1nm/25nm) T= 91 %Intrinsic los: 5% p
8、er interparticle spacing T= 95 %(Calculated for 25 nm Ag particles spaced by 75 nm)dd V+VVT=1+ V/2V) 21The Role of Defects and DisorderReflectionsMetal DepositionLift OfSpin coatingExposureDevelopmentThin layer of PMAReady to testGeneration of Arrays by e-beam LithographyGeneration of Arays by e-bea
9、mLithography Aray of 50 nm diameter Au dots spaced by 75 nm God control over particle size, shape, interparticle spacingSEM Images of Nanoparticle Arrays50 nmSEM Images of Nanoparticle AraysTLDetectorArrayPolarization filterWhite light sourceExtinction measurementFar-field Spectroscopy on a Au Nanop
10、article Aray EM coupling between particles breaks the rotational symmetry of a single particle3.03.23.43.63.84.00.0.20.40.60.81.0Extinction (a.u.)Angular fequncy !(105rad/s)UTL0TL!Extinction(a.u.)Al r ency (1015rad/s)S.A. Maier et. al, Phys. Rev. B 65, 193408-19341 (202).Far-field Spectroscopy on a
11、AuNanoparticle Aray Probes dispersion relation at k=0(Because d = interparticle spacing)T L k!0T!0L!00d2!2!“dLongitudinal polarizationLTTransverse polarizationObservation of Near-field Coupling in Particle AraysObservation of Near-field Couplingin Particle Arays75101253.103.123.143.163.183.203.23.24
12、Plasmon peak (1015rad/s)Spacing d(nm)T L k !0T!0L0d!2!“0T!0L!0 Peak splitting vanishes with increasing interparticle spacing d as d -3Dependence of Mode Spliting on Interparticle SpacingDependence of Mode Spliting onInterparticle SpacingExperiments on AFM Asembled AraysDyeFar-fielddetectionExcitatio
13、n using a scaning near-field optical microscope Transport along metal nanoparticle aray Detection of dye luminescence in far-fieldExperiments on AFM AsembledAraysAFM Manipulation of Latex Beads with DyesAFM anipulation of Latex Beadswith DyesTopography Fluorescence (inverted log)Luminescence from Si
14、ngle Latex SpheresLuminescence from Single LatexSpheresS.A.Maier, PhD Thesis CalTech 203Transport experimentGren/blue curves luminescent particle on a wireRed/black curves luminescent particles next to a wireIf no transport ocurs, fluorescence wil only be colected when the tip is directly on top of
15、the dye IdeaExperimentDistance (m)Fluorescencesignal(a.u.)0.0 0.4 0.8 1.2 1.6-0.20.20.61.01.4Transport experimentThe Future of Metal OpticsPhotonics Basic building blocks More complex architectures Aplications in biology for “Optical microscopy” ? Aplications in high-density optical data storage ? F
16、undamental studies of light-mater interaction1 m* R.M. Dickson et al., J. Phys. Chem. B 104, 6095-6098 (200)*The Future of Metal OpticsThe Future of Metal Optics*Fig 1. Integration of plasmonic elements onto Si-based microphotonic chips. SEMimages are of actual photonic devices (Vlasov).The Future o
17、f Metal OpticsAdition to Lecture #1:Localization and Guiding ofSurface Plasmon Polaritonsin Random NanostructuresBozhevolnyi et al., Physics Review Letter89, p186801-1 (2002)Optics in Nanostructured MediaOrdered media: photonic band gap! l“#/2! l“/2#Disordered media: localization (multiple scatering
18、)Optics in Nanostructured Media Both inhibit light propagation Both in a limited range of frequencies Both require a large refractive index contrastPhotonic crystals confine thelight inside the defectCan the same thing can be done in randommedia?Can guide lightthrough bends!Waveguiding in Photonic C
19、rystalsWaveguiding in Photonic CrystalsThis paper: First observations of confinement due torandom corugations created by surface features.Light(SP)Surface corugationPropagation of SPs: SurfacePlasmon PolaritonConfining mechanism:localization, i.e. multiplescatering and interferencethat prevents the
20、light frompropagating.Waveguiding in Random MediaWaveguiding in Random MediaFabricating Random NanostructuresRandomly positioned Au nanoscatterers lead to strong SP localization 45 nm thick Au layer thermallyevaporated onto glas substrate Resist is deposited on Au layer and6 x 18 m2rectangular areas
21、 paterned Random cordinates withineach rectangle exposed using anelectron beam Exposed region removed and2ndAu layer evaporated Remaining resist is etchedaway leaving disordered araysof 45 nm high gold bumpsGlas SubstrateResist LayerGold LayersBozhevoloyi, et al., Physical Review Letters, 86 (2001)Fabricating Random NanostructuresA 2- and 4-m widechannel were left free ofscatterers for SPP guidingTwo regions of randomly fabricatednanoparticles. Number density of (a)n1= 37.5 m-2and (b) n2= 50 m-2
