Cold mirror based on High-Low-High refractive index dielectric materials

Transcription

1 Cld mirrr based High-Lw-High refractive idex dielectric materials V.V. Elyuti.A. Butt S.N. Khia Samara Natial Research Uiversity 34 skvske Shsse Samara Russia Image Prcessig Systems Istitute Brach f the Federal Scietific Research Cetre Crystallgraphy ad Phtics f Russia Academy f Scieces 5 ldgvardeyskaya st Samara Russia Abstract I this paper a desig fr a multilayer dielectric cld mirrr based TiO / SiO ad TiO /gf alteratig layers is preseted. A cld mirrr is a specific dielectric mirrr that reflects the cmplete visible light spectrum whereas trasmittig the ifrared wavelegths. These mirrrs are desiged fr a icidet agle f 45 ad are mdeled with multilayer dielectric catigs similar t iterferece filters. Our desiged mirrr based TiO /SiO shws a average trasmissi f less tha 5 % i the spectrum rage f m whereas it has a average trasmissi f 95 % i the spectrum rage f m. Keywrds: Cld mirrr; TiO ; gf ; SiO ; dielectric materials. Itrducti Thi film ptics is a well-develped techlgy ad may devices such as passbad filters stpbad filters plarizers ad reflectrs are successfully develped with the help f multilayer dielectric thi films [-4]. These ptical elemets cmprise f alteratig layers f high ad lw refractive idex materials with specific thickesses ad awareess f their refractive idex ad absrpti. ultilayer dielectric filters are based the priciple f multiple reflectis that takes place betwee the iterfaces f high ad lw idex materials. Distributed Bragg Reflectrs (DBRs) are e f the widely used filters which are quarter wave thick f the ceter wavelegth. The high reflecti regi f a DBR is kw as the DBR stpbad ad ca be btaied by the refractive idex ctrast betwee the cstituet layers [5]. A cld mirrr is a specific dielectric mirrr that reflects the visible light spectrum while trasmits the ifrared wavelegths. These mirrrs wrk the priciple f multiple reflectis betwee high ad lw idex material iterface. The visible spectrum f light spas ~ m ad the regi beyd 770 m i the ear ifrared which is heat. Radiatis frm a tugste lamp ctai at least six times as much heat as useful light i the visible spectrum. The term cld light defies the radiati i which the IR spectrum is remved [6]. A ht mirrr is just the ppsite f cld mirrr which is desiged t reflect ifrared regi while trasmits the visible prti f the beam. These mirrrs ca separate visible light frm UV ad NIR which helps i separatig the heat frm the system as shw i figure. Cld mirrrs have may practical applicatis such as i prjectrs cpy machies medical istrumets ad fibre ptical illumiatis [6 7]. Visible light IRradiati Light surce Fig.. Schematic f a cld mirrr.. Theretical basis f multilayer structure Csider a multilayer dielectric system surruded by a evirmet. Light frm the surce falls the system at a agle α 0. Fr this purpse wave frt ca be csidered as plaar. T calculate the spectral trasmittace ad reflectace itesity fr the p- ad s-plarized light matrix methd is used: m Ts( ) ts Rs( ) rs () 3 rd Iteratial cferece Ifrmati Techlgy ad Natechlgy 07 5

2 Cmputer Optics ad Naphtics / V.V. Elyuti.A. Butt S.N. Khia m Tp( ) tp Rp( ) rp () where t s r s amplitude trasmissi ad reflecti cefficiets f the multilayer iterferece system fr s-plarized light whereas t p r p trasmissi ad amplitude reflecti cefficiets fr p-plarized light. Nw we will ly csider s- plarizati because equatis fr bth s ad p plarizati are related till equati (7). Amplitude cefficiets are determied frm the fllwig equatis: t s m i m im m s m s s m s (3) m i m im m rs m i m im m s m s s m s s m s s m s (4) where 0 m the effective refractive idices f the substrate ad the evirmet respectively; m i j s elemets f the characteristic matrix s fr s-plarized light: m im... s s s s s 3s qs qs qs ims ms (5) q Number f layers. I the expressi (5) matrices ( ) k k q determie the prperties f each idividual layer f the ptical filter. Filter desig eeds layers with high ad lw refractive idices. Therefre the spectral characteristics are described by matrices multiplyig: i cs( ) si( ) isi( ) cs( ) i cs( ) si( ) isi( ) cs( ) q i iqsi( q ) cs( q ) cs( q ) si( q ) q p i cs( q) si( q) q iqsi( q ) cs( q ) (6) where φ k phase thickess fr s- plarized light which is calculated by the fllwig equatis: h cs( ) h cs( ) h cs( ) q q q q q q h q cs( q ) (7) where h k the physical thickess f the layers m ; α k the agles f refracti i the layers; k effective idexes refractive f the layers which depeds the wavelegth. I this case the agle f refracti i the layers is 45 degrees relative t the rmal. The mai differece i calculatis betwee s- ad p- plarized light is specified i (8) ad (9) equatis. cs( ) cs( ) s s / cs( ) / cs( ) p p (8) (9) The agle f refracti i the layers is calculated by the equatis (0). 3 rd Iteratial cferece Ifrmati Techlgy ad Natechlgy 07 6

3 arccs si ( ) Cmputer Optics ad Naphtics / V.V. Elyuti.A. Butt S.N. Khia arccs si ( ) (0) Trasmissi f a uplarized light is calculated as a average f T s ad T p : T (TsT p) () By usig these equatis the trasmissi spectrum f the multilayer TiO /gf filter was pltted with the help f Java prgramig alg with the trasmissi spectrum geerated by cmmercially available pe surce filter Ope filter. Their respse is fairly cmparable as shw i figure % deled by Java prgram deled by Ope filter sftware Wavelegth (m) Fig.. Trasmissi spectrum f cld mirrr mdeled by Java prgrammig ad pe surce sftware: Ope filter. 3. Filter desig I the desigig f ptical filters the behaviur f the ttal multilayer system is estimated the basis f the prperties f the idividual layers i the stack [8]. Therefre t achieve the ptimum perfrmace it is sigificat t ptically characterize ad accurately determie the thickess f the idividual layers. I this wrk cld mirrrs are desiged i the wavelegth rage f m by usig pe surce sftware Ope Filter t selectively pass the wavelegths f iterest ad rejectig the udesired wavelegths i the visible spectrum. TiO SiO ad gf materials are carefully selected based their high ad lw refractive idices respectively. TiO is a vital dielectric material with a wide bad-gap eergy ad high refractive idex that ca make it useful i the fabricati f multilayer thi films due t its high ptical prperties. Fr istace its high trasmittace ad high refractive idex i the visible regi ( m) make it valuable t be emplyed i the prducti f the ptical filter ad widw glazig [9 0]. Layers made f xides are harder tha thse made f flurides sulphides r semicductrs. Thus they are ideal t be used expsed surfaces. Semicductr materials shuld be avided i filters which have t be used ver a wide rage f temperatures because their ptical cstats ca chage csiderably. The pe filter uses trasfer matrix methd t aalyze the trasmissi ad reflecti f light frm layers based thickess ad type f materials. Desigs are ptimized t maximum the trasmissi required at wavelegths usig eedle sythesis methd (additi f thi layers called eedle ad aalyze trasmissi till the best results btaied) []. The thickesses f the layers fr cld mirrr based TiO /gf ad TiO /SiO are shw i table. Bth mirrrs have 0 layers with almst cmparable ttal thickess. Special atteti has bee give t keep the thickess f the filters withi ecmic limits. Assumig the icidet agle f u-plarized light equals 45 these mirrrs have reflective prperties i the spectral rage frm m ad m up t 95 % ad 5 % respectively as shw i figure 3. Fr all dielectric stack filters the trasmissi depeds the agle f icidece. The cetral wavelegth f the FP filter shifts tward the smaller wavelegths as the agle f icidece is icreased. Whe the icidet agle f light decreases frm 45 t 0 the trasmissi spectrum shifts frm 70 t 750 m. 3 rd Iteratial cferece Ifrmati Techlgy ad Natechlgy 07 7

4 4. Cclusi Cmputer Optics ad Naphtics / V.V. Elyuti.A. Butt S.N. Khia I this wrk we preseted the mdelig results f cld mirrrs based TiO /gf ad TiO /SiO fr 45 f u-plarized icidet light by usig java prgrammig ad cmmercially available Ope surce sftware Ope filter. Bth mirrrs shw the reflecti f 95% i the spectral rage f m ad 95% f trasmissi i the spectral rage f m. The desigs are ptimized t maximum the trasmissi required at wavelegths usig eedle sythesis methd. We bserved a right shift i a spectrum whe the agle f icidece f light was reduced frm 45 t 0. Table. Layer thickesses f TiO /gf ad TiO /SiO based Cld mirrrs. Layer. aterial Thickess (m) Layer. aterial Thickess (m) TiO 4 TiO 5 gf 4 SiO 3 TiO 45 3 TiO 55 4 gf 84 4 SiO 8 5 TiO 6 5 TiO 55 6 gf 7 6 SiO 65 7 TiO 43 7 TiO 44 8 gf 87 8 SiO 99 9 TiO 44 9 TiO 5 0 gf 07 0 SiO 0 TiO 66 TiO 7 gf 90 SiO 9 3 TiO 68 3 TiO 7 4 gf 30 4 SiO 3 5 TiO 48 5 TiO 54 6 gf 8 6 SiO 06 7 TiO 87 7 TiO 93 8 gf 54 8 SiO 53 9 TiO 79 9 TiO 80 0 gf 8 0 SiO 8 Ttal thickess 639 Ttal thickess Passbad (%) Reflected bad Trasmissi spectrum f TiO /gf mirrr Trasmissi spectrum f TiO /SiO mirrr Reflecti spectrum f TiO /gf mirrr Reflecti spectrum f TiO /SiO mirrr Wavelegth (m) Fig. 3. Trasmissi ad reflecti spectrum f the cld mirrr i the wavelegth rage f m. Ackwledgemets This wrk was supprted by the iistry f Educati ad Sciece f the Russia Federati ad the Russia Fudati fr Basic Research (grat N fi_m fi_m). Refereces [] acled HA. Thi film ptical filters. cgraw-hill 989. [] Kazaskiy NL Serafimvich PG Ppv SB Khia SN. Usig guided-mde resace t desig a-ptical spectral trasmissi filters. Cmputer Optics 00; 34(): [3] Kazaskiy NL Kharitv SI Khia SN Vltvskiy SG Strelkv YuS. Simulati f hyperspectrmeter spectral liear variable filters. Cmputer Optics 04; 38(): rd Iteratial cferece Ifrmati Techlgy ad Natechlgy 07 8

5 Cmputer Optics ad Naphtics / V.V. Elyuti.A. Butt S.N. Khia [4] Kazaskiy NL Kharitv SI Khia SN Vltvskiy SG. Simulati f spectral filters used i hyperspectrmeter by decmpsiti vectr Bessel mdes Prc. f SPIE 05; 9533: 95330L-7pp. [5] Butt A Fmchekv SA Ullah A Habib Ali RZ. dellig f multilayer dielectric filters based TiO /SiO ad TiO /gf fr flurescece micrscpy imagig. Cmputer Optics 06; 40(5): DOI: 0.09/ICECUBE [6] Baumeister PW. Optical catig techlgy. SPIE Press bk 004. [7] Guether BD. der Optics. Oxfrd Uiversity Press 05. [8] Hiczeweski DS Hiczeweski Tepehe FZ Tepehe GG. Optical filters frm SiO ad TiO multi-layers usig sl-gel spi catig methd. Slar Eergy aterials ad Slar Cells 005; 87(-4): [9] Hasa alek AB Haseeb ASA asjuki HH. Ivestigatis TiO ad Ag based sigle ad multilayer films fr widw glazigs. ARPN Jurals f Egieerig ad Applied Scieces 00; 5: 8. [0] Butt A Fmchekv SA. Thermal effect the ptical ad mrphlgical prperties f TiO thi films btaied by aealig a Ti metal layer. J. Krea Phys. Sc. 07; 70(): [] Laruche S artiu L. Optical filters: Ope-surce sftware fr the desig ptimizati ad sythesis f ptical filter. Appl. Opt. 008; 47(3): C9 C30. 3 rd Iteratial cferece Ifrmati Techlgy ad Natechlgy 07 9