High-Performance Transmission of Surface Plasmons in Graphene-Covered Nanowire Pairs with Substrate

Da Teng,Qiongsha Huan,Yanan Tang,Yongzhe Zhao,Kai Wang

doi:10.3390/nano9111594

Abstract

Graphene was recently proposed as a promising alternative to support surface plasmons with superior performances in the mid-infrared range. Here, we theoretically show that high-performance and low-loss transmission of graphene plasmons can be achieved by adding a silica substrate to the graphene-covered nanowire pairs. The effect of the substrate layer on mode properties has been intensively investigated by using the finite element method. Furthermore, the results show that inserting a low index material layer between the nanowire and substrate could compensate for the loss accompanied by the substrate, thus the mode properties could be adjusted to fulfill better performance. A reasonable propagation length of 15 μm and an ultra-small normalized mode area about ~10−4 could be obtained at 30 THz. The introduction of the substrate layer is crucial for practical fabrication, which provides additional freedom to tune the mode properties. The graphene-covered nanowire pairs with an extra substrate may inspire potential applications in tunable integrated nanophotonic devices.

Highlights

Surface plasmons (SPs) [1], which are surface electromagnetic waves propagating along a metal-dielectric interface, have been widely investigated for applications of compact and high-performance optical devices [2] far beyond the diffraction limit [3]
Metal-based plasmonic devices suffer from large Ohmic losses and lack of tunability, hindering the applications under some circumstances
As we have shown before, adding a dielectric substrate to the graphene-covered nanowire pairs is cruAcsiawl efohrapvreaschtiocwalnfabberfoicraet,ioadn,dianngdapdrioevleidctersicasdudbisttiroantaeltofrteheedogmrapthoenfuel-fciollvbeerettdernawnaovweigrueipdainirgs pisercfrourcmiaalnfcoer. pFriancatilclya,l fwabericinavtieosnt,igaanteddprtohveidiensflaudendciteionofal dfrieffeedreonmt tsoufbusltfiralltebemtteartewriaalvsegounidtinhge wpearvfoergmuiadnicneg. pFirnoaplelyr,tiwese, iannvdestthigearteesdultthseciannflbueensceeenofindiTffaebrleen1t .sHubesrter,aRte1 m= Rat2e=ri5a0lsnomn,tDhe=w50avnemgu, i[dh,iHng]

Summary

Introduction

Surface plasmons (SPs) [1], which are surface electromagnetic waves propagating along a metal-dielectric interface, have been widely investigated for applications of compact and high-performance optical devices [2] far beyond the diffraction limit [3]. Metal-based plasmonic devices suffer from large Ohmic losses and lack of tunability, hindering the applications under some circumstances Reports from both theoretical and experimental studies have shown that graphene [23], a two-dimensional carbon material, can support SPs [24,25]. WWhheenn nnoo ssuubbssttrraattee aanndd ggaapp aarree uusseedd ((sseeee FFiigguurree 11aa)),, wwhhiicchh ccoorrrreessppoonnddssttootthheeggrraapphheennee--ccoovveerreeddnnaannoowwirireeppaairirininaairir,, tthhee ssttrroonngg ccoouupplliinngg ooff SSPPss aatt ttwwoo ggrraapphheennee--ddiieelleeccttrriicc iinntteerrffaacceess lleeaaddss ttoo mmooddee ffiieelldd ccoonncceennttrraattiioonn iinn tthheeggaappoofftthheetwtwoonnaannoowwirierse.sI.nInFiFgiugruer2eb2,bth, tehgeragprahpehneen-ceo-vcoerveedrendannoawnoirweipreaipraisirdiisredcitrleyctplylacpeldacoend aonsilaicsailsiucabssturabtsetrwaittehwHit=h1H0 n=m1. Nanomaterials 2019, 9, x FOR PEER REVIEW introduction of a substrate and air gap slightly affect the mode size (see dotted brown and solid blue c5ucr).vNesoitnicFeiagbulyre, w5ce).fiNnodtitcheaatbtlhy,ewdeotfitendd bthroawt tnhecudrovtteeadnbdroswolnidcbulruvee caunrdvseoalirde bnleuaerlcyuorvveeralraepnpeeadrliyn oFvigeurlraep5peedxcienpFtihgiugrhee5r efrxecqeupet nhcigiehseirnfrFeiqguuerenc5ice.sTinhiFsimgueraen5sct.hTaht iasltmhoeaungshthaastuablsthtroauteghisaadsudbesdtrtaotethise agdradpedhetnoet-hceovgerraepdhennaen-coowvierreedpaniarn, otwheireexpcaeilrl,etnhteoepxctieclalelnpteorpfotircmalapnecrefocromualdncbeecomuladinbteaimneadin, twaihniecdh, willhuiscthraitlleussttrhaetefseathsiebfieliatysiboiflitpyroacftpicraalctaicpapllaicpaptiloicnastioonf sthoef tghreagprhaepnhee-ncoev-ceorvederendannoawnoirweirpeapiraiwr withitha asusbusbtsrtartaet.e. TThhee ttuunnaabbiilliittyy ooff tthhee wwaavveegguuiiddiinngg ppeerrffoorrmmaannccee iiss ooff ggrreeaatt iimmppoorrttaannccee ffoorr pprraaccttiiccaall aapppplliiccaattiioonnss. DDepepenenddenecneceofofthteheFGFPGMPMprporpoeprteiretsieosnocnhcehmeimcailcaplopteontteinalt.ia(la.) E(af)feEctffivecetimveodmeoidndeeixn;d(ebx); p(bro) ppargoaptaiognatlieonngtlhen; g(ct)hn; o(rcm) anloizremdamlizoedde msizoed;eansidze(;d)aFnodM(.dT) hFeoMdo.ttTehdebrdoowttnedcubrrvoewfnor c[uhr,Hve,Rf]o=r [0h,,0H,1,R00] ]=n[m0,,0s,1o0li0d] nbmlu,e csuorlivde fbolru[eh,cHu,rRv]e= f[o10r,1[0h,1H0,0R]]n=m,[a1n0d,10so,1l0id0]rendmcu, ravnedfosro[lhi,dH,rRe]d= c[1u0r,v1e0,5fo0]r n[hm,H. ,fR0 i]s=30[1T0H,10z,5a0n]dnμmc .ranf g0 eiss f3ro0mTH0.2z eaVndtoμ1ceVra.nOgtehserfrpoamram0.2eterVs atore1theeVs.aOmtehaesr Fpiagruarme e2t.ers are the same as Figure 2

Discussion

Conclusions