APPLIED OPTICS-Silicon wire grid polarizer for ultraviolet applications

Siliconwiregridpolarizerforultravioletapplications

ThomasWeber,1StefanieKroker,1,*ThomasKäsebier,1

Ernst-BernhardKley,1andAndreasTünnermann1,2

1

Friedrich-Schiller-UniversityJena,Abbe-CenterofPhotonics,InstituteofAppliedPhysics,

Albert-Einstein-Strasse15,07745Jena,Germany

2

FraunhoferInstituteofAppliedOpticsandPrecisionEngineering,Albert-Einstein-Strasse7,

07745Jena,Germany

*Correspondingauthor:stefanie.kroker@uni jena.de

Received17September2014;revised3November2014;accepted6November2014;

posted7November2014(Doc.ID223302);published26November2014

Wepresentasiliconwiregridpolarizeroperatingdowntoawavelengthof300nm.Besidesmetallicgratingmaterials,semiconductorsalsoofferappropriatematerialpropertiestorealizewiregridpolar-izersintheultraviolet(UV)spectralrange.Thepresentedpolarizerwithaperiodof140nmwasrealizedbymeansofelectronbeamlithographyanddryetchingusingamorphoussiliconasthegratingmaterial.Atawavelengthof365nm,atransmissionof42%andanextinctionratioof90(19.5dB)aremeasured.ThespectralbandwidthofthesepolarizersintheUV-spectralrangeisabout100nm.©2014OpticalSocietyofAmerica

OCIScodes:(050.2770)Gratings;(220.4241)Nanostructurefabrication;(230.5440)Polarization-selectivedevices.

doc.guandang.net

1.Introduction

SinceHertzdemonstratedthepolarizingcharacter-isticsofawiregridin1888[1]andBirdandParrishpublishedthefirstwiregridpolarizerfortheinfrared(IR)spectralregionin1960[2],wiregridpolarizershavebeenofgreatinterestinthefieldsofspectros-copy,high-resolutionmicroscopy,andimagingsystems.Thesedevicestypicallyconsistofparallelmetallicwiresonatransparentsubstrate.Theopti-calfunctionischaracterizedbythesuppressionofTE-polarizedlight(electricalfieldvectorparalleltothewires),whilethetransmissionofTM-polarizedlight(electricalfieldvectorperpendiculartothewires)remainshigh[3].Thedegreeofpolarizationisgivenbytheextinctionratio,whichistheratioofTM-andTE-polarizedlight.Thespectralworkingrangeofthesedevicesisdefinedbythegratingperiodandthegratingmaterial.Advancesinthe

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APPLIEDOPTICS/Vol.53,No.34/1December2014

fieldsofmicro-andnanotechnologyinthelastdecadeallowforthefabricationofwiregridpolarizerswithgratingperiodsof100nmandbelow[4–6],aswellastheuseofvariousmetallicgratingmaterialssuchasaluminum[7],chromium[8],iridium[9],ortungsten,enablingabroadbandopticalfunctiondowntoawavelengthof193nm[10].Themostcommongra-tingmaterialisaluminum,offeringabroadworkingrangefromtheIRtotheultraviolet(UV)spectralrangewhenthegratingperiodischosenadequately.Besidesthegratingperiod,thegratingheightanddutycycledefinedbytheratioofridgewidthandgra-tingperiodinfluencetheopticalpropertiesofawiregridpolarizer[11].

Todate,littleattentionhasbeengiventosemicon-ductorsasgratingmaterialsforwiregridpolarizers.In[12,13]thetransmissionpropertiesofamorphoussilicongratingswithdifferentgratingperiodswereinvestigatedatawavelengthof633nm,butnospectralcharacteristicswerediscussedormeasured.Furthermore,silicongratingsshowingtheguidedmoderesonanceeffectwereusedasnarrowband