《Graphene-based-optical-modulator-超全面的石墨烯介绍课件.ppt》由会员分享，可在线阅读，更多相关《Graphene-based-optical-modulator-超全面的石墨烯介绍课件.ppt（33页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、Graphene and Graphene-based optical modulatorTinna Zhang15th,June,2011OutlinenWhat is graphene?nHow it is madenPropertiesnFuture ApplicationsnA graphene-based broadband optical modulatorWhat is graphene?n“Imagine a piece of paper but a million times thinner.This is how thick graphene is.nImagine a m
2、aterial stronger than diamond.This is how strong graphene is in the plane.nImagine a material more conducting than copper.This is how conductive graphene is.nImagine a machine that can test the same physics that scientists test in,say,CERN,but small enough to stand on top of your table.Graphene allo
3、ws this to happen.nHaving such a material in hand,one can easily think of many useful things that can eventually come out.As concerns new physics,no one doubts about it already.From a recently interview with Andre Geim.n2-dimensional hexagonal lattice of carbonnsp2 hybridized carbon atomsnBasis for
4、C-60(fullerenes),nanotubes,and graphitenAmong strongest bonds in natureWhat is graphene?A.K.Geim&K.S.Novoselov.The rise of graphene.Nature Materials Vol 6 183-191(March 2007)5 mmAndre Geim Kostya NovoselovThe Nobel Prize in Physics for 2010Lattice effects:Ripples in graphene2D membranes embedded in
5、3D space have a tendency to get crumpled.These dangerous fluctuations can be suppressed by an anharmonic coupling between bending and stretching modes.Result:the membranes can exist,but with strong height fluctuations.A typicalsnapshot of graphene at room temperature.The size ofheight fluctuations i
6、scomparable tothe lattice size.Productionn2008,exfoliation-$100,000,000/cm2n2009,epitaxial on SiC-$100/cm2nthen,Korean,CVD,30inchesn2011,the Institute of Electronic Materials Technology and Department of Physics,Warsaw University announced a joint development of acquisition technology of large piece
7、s of graphene with the best quality so far.In April,patentGraphene:Atomic structureIn momentum spaceDirac Cone“Ultra relativistic”Solid State at low speed of lightNovoselov et al,Science 306,666(2004)Electric field effect(A)Typical dependences of FLGs resistivity on gate voltage for different temper
8、atures(T=5,70,and 300 K for top to bottom curves,respectively).(B)Example of changes in the films conductivity obtained by inverting the 70 K curve(dots).(C)Hall coefficient RH versus Vg for the same film;T=5 K.(D)Temperature dependence of carrier concentration n0 in the mixed state for the film in(
9、A)(open circles),a thicker FLG film(squares),and multilayer graphene(d 5 nm;solid circles).Red curves in(B)to(D)are the dependences calculated from our model of a 2D semimetal illustrated by insets in(C).Klein paradox electrons go through potential barriers Penetration of particlesthrough potentialb
10、arriers.The transmissionprobability T is directionally-dependent.For high barriers(V E)Anomalous quantum Hall effectnGraphene shows integer QHE shifted by 1/2 integernNon-zero conductivity as charge carrier dentsity-zero.nHall conductivity xy(red)and resistivity xy vs.carrier concentration.nInset:xy
11、 in 2-layer graphite.nHalf-integer QHE unique to monolayer.Optical propertiesnunexpectedly high opacity for an atomic monolayer,with a startlingly simple value:it absorbs 2.3%of white light,where is the fine-structure constantna consequence of the unusual low-energy electronic structure of monolayer
12、 graphene that features electron and hole conical bands meeting each other at the Dirac pointIt has been shown that graphene/graphene oxide system exhibits electrochromic behavior,allowing tuning of both linear and ultrafast optical propertiesSaturable absorptionnsuch unique absorption could become
13、saturated when the input optical intensity is above a threshold value.nThis nonlinear optical behavior-saturable absorption,the threshold value-saturation fluence.nGraphene can be saturated readily under strong excitation over the visible to near-infrared region,due to the universal optical absorpti
14、on and zero band gap.nThis has relevance for the mode locking of fiber lasers,where fullband mode locking has been achieved by graphene-based saturable absorber.Due to this special property,graphene has wide application in ultrafast photonics.Moreover,the ultrafast optical response of graphene/graph
15、ene oxide layers can be tuned electricallyApplicationsn“space elevator”cablenHydrogen storagenSingle molcule gas detectionnGraphene based quantum computationnThermal mangement materials-Thermal interfacial materialsnSolar cellsnUltracapacitorsnGraphene biodevicesnAnti-bacterial24Graphene Transistors
16、Hybrid FET can switch 14X faster than Silicon alone.Uses less power and runs cooler.Compatible with todays lithography and etching fabrication technologies.UCLA has demonstrated circuits running at 300GHz.IBM Details Worlds Fastest and Smallest Graphene Transistor-155GHz,155billion cycles/sIntegrate
17、d circuitsnHigh carrier mobilitynLow noisenFast responsenCompactt footprintGraphene-based optical modulatornStrong light-graphene interactionnBroadband operationnUltrafast modulation speednCompatibility with CMOS processingnCompact footprintnLow operation voltagenTemperature toleranceMing Liu,Xiao Y
18、in,Erick Ulin-Avila,Baisong Geng,Thomas Zentgraf,Long Ju,Feng Wang,&Xiang Zhang,Nature,474,64(2011)Optical electroabsorption modulatornBy applying a drive voltage between the graphene and the waveguide,one can tune the Fermi level of the graphene,and therefore modulate the total transmission.nModula
19、tion depth:0.1dBm-1Dirac point:EF(VD)=h0/2Gigahertz operation of the device at various drive voltages is obtained,the bandwidth is limited by the parasitic response of the deviceGraphene-based optical modulatornWhite source from a supercontinuous lasernElectronic band dispersion of the grapheneChall
20、engenIts compatibility with the existing integrated electronics platformnReduce the total resistance of the circuit and the drive voltagenReduce the power consumption and chirpConclusionnGraphene is a novel material with very unusual propertiesnVariety of possible practical applications.nDigital devices have a bright and promising future.