POLARIZATION PRESERVING REFLECTED BEAM SPLITTER

Transcription

1 The 6th Saudi Engineeing Confeence, KFUPM, Dhahan, Decembe Vol POLAIZATION PESEVING EFLECTED BEAM SPLITTE Mohamad A. Habli Infomation Engineeing Deatment, Sul Qaboo Univeity P.O. Box 33, Al-Khod, Mucat 3, Sulate of Oman Tel: , Fax: ABSTACT The deign of a olaization eeving eflected beam litte (PPBS i eented. The PPBS conit of a V-haed abobing ubtate coated with a ingle thin film laye. The PPBS oeate in the UV egion. The owe eflection coefficient ange fom 69%-9% fo angle of incident anging fom degee eectively. Keywod: Polaization eeving, eflected beam litte, Single-laye coating, abobing ubtate, UV ange. الملخص تصميم حها ز للمحافظ على الاستقطاب الضوءي بعد الانعكاس. الجهاز يتالف من مادة ممتص على شكل حرف V و مغطاه بمادة اخرى رقيقة. الجهاز يعمل في المنطقة المافوق البنفسجية. درجة الانعكاس تراوحت بين ٦٥% - ٩٠% لزوايا اسقاط بين ٨٥-٨٩ درجة.. INTODUCTION Polaization eeving device ae often needed in otical ytem to eeve the olaization tate of the incoming light afte it goe though eflection o miion. A numbe of olaization eeving device ae eoted in liteatue. Thee device conit of two aallel o othogonal eflected ubtate coated with aoiate thin film laye [Azzam et al, 99, 98, 985]. In thee device, the incoming beam ha to eflect off two ubtate befoe it can etun back to it oiginal olaization. In thi ae we ae intoducing the olaization eeving eflected beam litte PPBS. The PPBS lit the incoming beam into two beam with two diffeent diection. The tate of olaization of the two beam i the ame a the incoming beam. The advantage that the PPBS ha ove the eviou eoted device i that the PPBS eeve the olaization of the incoming beam without the need to go though a econd eflection.

2 Vol Mohamad A. Habli The PPBS conit of a V-haed abobing ubtate coated with a ingle thin film laye. The deigned PPBS oeate in the ulta-violate (UV egion. Two diffeent mateial ae conideed a ubtate fo the PPBS. The fit mateial i Gemanium Ge with a comlex eflection index N.56-j4.669 at a wavelength λ4.4 ev o 8.93 nm. The econd mateial i Gallium Antimonide GaSb with a comlex eflection index N.5-j4.3 at a wavelength λ4. ev o nm [Aen et al, 983]. The owe eflection coefficient of the PPBS ange fom 69-9% fo angle of incident anging fom degee.. THEOETICAL BACKGOUND Conide the tuctue hown in Fig.. The tuctue need to be oitioned ymmetically in the ath of the oiginal beam a hown in Fig.. The tuctue conit of a V-haed abobing ubtate of a comlex index of efaction N n -jk. The ubtate i laced in a medium of efactive index N. In thi ae we ued N fo ai. Both uface of the ubtate ae coated with a ingle thin film laye of index of efaction N. The film ha a unifom thickne d ove the total aea of both uface of the ubtate. The ubcit,, and denote the incidence, film, and ubtate media, eectively, fo both uface. Thee media, ae aumed to be linea, homogeneou, iotoic, and ae eaated by aallel-lane inteface. Suoe that a linealy olaized monochomatic lane wave i incident on both ide of the tuctue at an angle φ. The oientation that the incident wave make with the -axi i 45 o a hown in Fig.. The comlex amlitude eflection coefficient of the film-ubtate ytem fo any of the two ide of the ubtate can be witten in geneal a: [Bon, et al, 999]. ( + X (, υ υ υ / + υ υ X whee υ indicate the o olaization and X i given a: ( X j πζ e, ( In Eq. ζ i the nomalized film thickne and i equal to: whee d i the actual film thickne and ζ d / D φ, (3 D φ i the film thickne eiod and i given a: ( N N λ / D φ in φ. (4

3 Polaization Peeving eflected Beam Slitte Vol In Eq. 4 λ i the wavelength of the incident beam. Looking back at Eq., the and Fenel eflection coefficient fo the inteface on both uface of the tuctue ae given a: ( φ φ ( φ + φ (5 ( φ φ ( φ + φ in (6 in and fo the inteface they ae equal to: ( φ φ ( φ + φ (7 ( φ φ ( φ + φ in (8 in In ode to eeve the olaization of the incoming light the following equation ha to be atified: 45 o N N 45 o Φ δ δ d N Φ N d N 45 o Fig. The PPBS layout.

4 Vol Mohamad A. Habli ρ. (9 ewiting Eq. (9: ( Thi condition can be witten a a function of fou aamete: ( ζ, N, N F φ (, In thi ae we tudied the condition of the aid fou aamete that atify Eq.. 3. ESULTS AND ANALYSIS The ummay of eult fo the deigned PPBS uing Ge and GaSb ubtate ae hown in Table and eectively. The two Table how a lit of angle of incidence φ and thei coeonding nomalized ζ and actual film thicknee d, the owe eflecce and the magnitude and hae of ρ, ρ and ρ, eectively. The owe eflection coefficient i equal to: υ υ ( The owe eflection lited i fo each ide of the ubtate. Each ide of the ubtate eceive one-half of the intenity of the incoming light. It hould be mentioned that due to the abobing natue of the ubtate, the beam will lo ome of it owe. The eult in Table ae fo Ge whoe index of efaction N.56-j4.669 at a wavelength λ4.4ev o 8.93nm. The index of efaction of the thin film on both ide of the Ge ubtate N Table how the eult fo GaSb. The index of efaction of GaSb N.5-j4.3 at a wavelength λ4.ev o 93.36nm. The index of efaction of the thin film on both ide of the GaSb ubtate i N Suitable mateial fo ue a thin film fo N ae metallic thin film uch a (Gold, Silve, o Aluminum.

5 Polaization Peeving eflected Beam Slitte Vol Table. PPBS Deign table fo Ge N.56-j4.669, N 4.363, and λ 4.4 ev o 8.93 nm φ (degee ζ (m (% ρ d ρ (degee E E E E E E E E E E- Table. PPBS Deign table fo GaSb N.5-j4.3, N , and λ 4. ev o nm φ (degee ζ (m (% ρ d ρ (degee E E E E E E E E E E- 4. CONCLUSION A olaization eeving eflected beam litte (PPBS i intoduced that oeate in the UV egion. The two mateial that ae conideed a ubtate fo the PPBS ae Gemanium Ge with a comlex eflection index N.56-j4.669 at a wavelength λ4.4 ev o 8.93 nm and Gallium Antimonide GaSb with a comlex eflection index N.5-j4.3 at a wavelength λ4. ev o nm. The PPBS lit the incoming beam into two beam with equal intenity. The tate of olaization of both beam i the ame a that of the incoming beam. The owe eflection coefficient of the PPBS ange fom 69%-9% fo angle of incident anging fom degee eectively.

6 Vol Mohamad A. Habli 5. EFEENCES..M.A. Azzam and M.A. Habli, Bilaye coating fo light efaction without change of olaization Jounal of Moden otic, Vol. 39, No., 55-63, 99...M. Azzam and M.E. Khan, Polaization-eeving ingle-laye-coated beam dilace and axicon Alied Otic, Vol., , M. Azzam, imuleou eflection and efaction of light without change of olaization by a ingle-laye-coated dielectic uface Otic Lette, Vol., 7-9, D.E. Ane and A.A. Studna, Dielectic function and otical aamete of Si, Ge, GaP, GaA, GaSb, InP, InA, and InSb fom.5 to 6. ev Phyical ev. B, 7, , M. Bon and E. Wolf, Pincile of Otic: Electomagnetic Theoy of Poagation, Intefeence and Diffaction of Light, 7 th edition, Cambidge Univeity Pe, USA, 999.