Thiswritingtalksaboutpapernumberfiveinthelist.Thepaperisabouthowlightmovesinspecialmaterials.Thesematerialsarecalledphotoniccrystals.Theyhaveapattern.Thispatternisverysmall.Thepatternrepeats.Itislikethepatterninahoneycomb.Butitismuchsmaller.Lightmovesthroughthesematerials.Butitcannotmoveinallways.Somecolorsoflightcannotpass.Thisiscalledabandgap.Itislikeawallforlight.

Thepaperstudiesaspecificshape.Thisshapeisaring.Theringisverysmall.Itisonaflatsurface.Theringismadeofsilicon.Siliconisamaterialincomputerchips.Itisalsoinsolarpanels.Theringsitsonasheetofsilicondioxide.Thisislikeglass.Thescientistsmadethissmallring.Theyusedspecialtools.Theywantedtoseehowlightbehavesinsideit.

Lightisawave.Ithaspeaksandvalleys.Theringtrapslight.Thelightgoesaroundthering.Itmovesincircles.Thelightwavemustfitperfectly.Thewaveendmustmeetthewavestart.Thisisaresonance.Itislikepushingaswingattherighttime.Theswinggoeshigher.Forlight,itgetsstrongerinsidethering.

Thepaperasksaquestion.Whathappensifwechangethering'sshape?Thescientistsmadetheringnotperfectlyround.Theymadeitslightlydeformed.Theypushedonesidealittle.Theypulledtheotherside.Theringbecameanellipse.Anellipseislikeastretchedcircle.Ithasalongpartandashortpart.

Theysentlightintothisellipse.Thelightcamefromalaser.Alasermakeslightofonecolor.Thelighttraveledalongatinywire.Thiswireisawaveguide.Itislikearoadforlight.Thewiretouchedtheellipse.Thelightjumpedfromthewireintotheellipse.

Thelightmovedinsidetheellipse.Ittriedtogoaround.Butthepathwasnotthesameeverywhere.Thelongpathandshortpathweredifferent.Thelightwavecouldnotfitperfectlyanymore.Onecoloroflightcouldfitthelongpath.Anothercolorcouldfittheshortpath.Sonow,twocolorsoflightcouldbetrapped.Theycouldgoaroundatthesametime.

Thescientistsmeasuredthis.Theyfoundtwopeaks.Eachpeakwasacoloroflight.Thelightwasresonating.Theellipsehadtwo"sweetspots"forlight.Thisisdifferentfromacircle.Acirclehasonlyonemainsweetspotforonecolor.

Theydidmoretests.Theychangedthedeformation.Theymadetheellipselonger.Thetwopeaksmoved.Theymovedapart.Onecolorbecameredder.Theothercolorbecamebluer.Thegapbetweenthemgrew.Thisshowedapattern.Theshapecontrolsthelight.

Thepaperalsotalksaboutlightloss.Lightcanescapefromthering.Itcanbecomeheat.Thematerialcanabsorbit.Thescientistsmeasuredthisloss.Theyfoundtheellipsehadmorelossthanacircle.Thelighttraveledalongerpath.Ithadmorechancestobelost.Thisisaproblemfordevices.

Thisworkisimportantforsmalldevices.Wehavemanydevicestoday.Phones,computers,sensors.Theyuselighttosendinformation.Internetcablesuselight.Doctorsuselighttoseeinsidethebody.Lightcanbeusedforsensing.Itcandetectchemicals.Itcanmeasuretemperature.

Asmallringcanbeasensor.Putadropofliquidonit.Thelightinsidechanges.Thecolorpeakmoves.Wecanseethechange.Weknowwhatisintheliquid.Butacirclesensoronlyhasonepeak.Anellipsesensorhastwopeaks.Itgivesmoreinformation.Itcanbemoreprecise.Itislikehavingtwomeasuringtapesinsteadofone.

Thispapergivesthenumbers.Itgivesthesizeofthering.Theringhadadiameterof10micrometers.Ahumanhairisabout70micrometers.Sotheringismuchsmallerthanahair.Thedeformationwas20nanometers.Ananometerisonebillionthofameter.Itisvery,verysmall.

Thelightusedwasnearinfrared.Oureyescannotseeit.Ithasawavelengthof1550nanometers.Thisisgoodforcommunications.Ourinternetusesthislightcolor.

Thescientistsusedamethodcalledfiniteelementsimulation.Theyusedacomputer.Theytoldthecomputertheshape.Thecomputercalculatedthelight.Itshowedwherethelightwouldbestrong.Itshowedthecolors.Thentheymadetherealring.Theytestedit.Therealresultsmatchedthecomputerresults.

Otherpapershavedonesimilarwork.Papernumbertwointhelisttalksaboutlightincircles.Papernumberseventalksaboutdeformedringstoo.Butpapernumberfivefocusesontheellipse.Itgivesverycleardata.Itshowstherelationship.Therelationshipisbetweendeformationandthetwolightcolors.Therelationshipislinear.Thismeansifyoudeformmore,thecolorgapincreasesproportionally.Itisastraightlineonagraph.

Thisfindingisuseful.Engineerslikesimplerules.Asimplerulehelpsdesign.Ifyouwantasensorfortwospecificcolors,youcancalculatetheshape.Youknowhowmuchtostretchthecircle.

Thepaperalsomentionsfuturework.Thenextstepcouldbetouseothershapes.Asquarering.Atrianglering.Eachshapewilltraplightdifferently.Thelightpathwillhavecorners.Cornersmightscatterlight.Buttheymightalsocreateneweffects.Anotherideaistouseothermaterials.Siliconisgood.Butnewmaterialslikesiliconnitridemighthavelessloss.Theymightworkbetterforcertaincolors.

Theworldneedssmaller,faster,cheaperdevices.Lightisfasterthanelectricity.Lightchipsarethefuture.Theywillusestructureslikethissmallring.Theywillguidelight.Theywillprocessinformation.Theworkinpaperfiveisastep.Ithelpsusunderstandonesmallpart.Ithelpsuscontrollightbetter.Controliskeytotechnology.Bybendingashapealittle,webendlight.Wemakeitworkforus.

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