2009) 3( 22مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة المجلد رمایكرو مت )5 -3(ة لمنطقة األشعة تحت الحمراء تحضیر نوافذ بصری باستخدام مادة أوكسید األلمنیوم ، لیث ناظم عباس، سوزان علي حسن*عبد الرسول مجید بهاءإلطیف، خضیرعبد الحسین والتكنولوجیاوزارة العلوم الجامعة المستنصریة ،كلیة التربیة ، قسم الفیزیاء * الخالصة تم في هذا البحث تحضیر نوافذ بصریة تعمل ضمن الطول الموجي لمدى األشعة تحت الحمراء باستعمال طالء مایكرو ) 5- 3(بحیث یغطي النافذة الجویة (ZnSe)على قواعد من (Al2O3)غیر عاكس من مادة أوكسید األلمنیوم عند الطول % 97فباستعمال ثمان طبقات من أوكسید األلمنیوم وعلى جانبي القاعدة كانت أعظم نفاذیة بحدود . متر .مایكرومتر 4.4الموجي IBN AL- HAITHAM J. FOR PU RE & APPL. SCI VOL.2 2 (3) 20 09 Preparation of Optical Window in the Infrared Region (3- 5) µm Using Al2O3 Material A.K. Iltaif, B.A.Al-Hilli*, L.N.Abbas, S.A.Hasan Ministry of Science and Technology * Departme nt of Phsics , College of Education, Al- Mustansiriyah Unive rsity Abstract In this work opt ical window for infrared region was p repared by using Aluminu m O xide (Al2O3)material as antireflection coating on ZnSe substrate which covers the atmosp heric window 3-5µm. the maximum transition was 97% at a wavelen gth 0f 4.4µm. Introduction Ant ireflection p henomenon was first recognized by Raleigh and Fraunhofer in the 19 th century as a sp ontaneous p rocess on atmosp herically tarnished lenses (1). In 1934 Bauer (2) deduced that the reduction in reflectance is p rimarily due to interference p henomena. This p henomenon has been p ut in to good use in 1930 when the p rocess of vacuu m evaporation borrowed from the electronic industry , enabled the controlled industrial deposition to be introduced as what is subsequently called "antireflection coating (ARC)(3)".Nagendra and M ohan studied the antireflection coating p henomenon by the dep osition of more than one of thin film layers in series(4). Grebenshchikov et al. (5) have p ublished in 1946 the first book in antireflection coating of op tical surfaces including the multilay er coating. ARC's enter new st age when characteristic matrix theory is submitted and discussed by Abeles (6) in 1950. Hrep in (7) and Epst ein (8) p ut mathematical equations for designing op tical filters. Also, Wellford (9) d escribed a design of sin gle layer ARC's with t he aid of "Vector method". In all the optoelectronic devices and sy st ems the op tical windows can be considered as an op tical filters for a sp ecified sp ectral region. In ord er to minimize the losing p ower through reflection, it is useful to use the ARC technique for these windows (10). Novel design p rocedure of broad band multilay er ARC for op tical and optoelectronic devices were deduced by (11). The aim of this work is to manufacture infrared op tical windows by using multilayer ARC's (Al2O3) deposited on ZnSe substrates. The ory: When light incident from media (no) with angle ( Φo) on antireflection coating film (n1) deposited on subst rate of refractive index (ns). We obtain Rm ax (maximum reflectivity and Rm in (minimum ref lectivity ) if (12): ns≥n1≥no ���� = � (�����) (�����) � � �ℎ�� ���� = � � , �, … … [1] IBN AL- HAITHAM J. FOR PU RE & APPL. SCI VOL.2 2 (3) 20 09 ���� = � ��� ������� ��� ������� � � �ℎ�� ���� = � � , �� � ,… … [2] Where: n1d1 is the optical thickness of the film λ is wavelen gth of the incident light � = �2� �� ����� cos � Phase difference, d1 is a film thickness Thin film calculations (TF-CALC) program p ackage was used to calculate the p ercentage of transmission and reflection of co ating lay ers. Accordin g to our calculations, the followin g design was used to get a high transmission on ZnSe subst rate: (L8HL8) L: is a lay er with a low refractive index such as Al2O3 H: is a layer with a high r efractive index such as ZnSe From this design the maximum transmission was about 82.3% at the wavelength of 4.55µm for one face co ating as shown in Fig. (1) And about 99.8% for both faces coatin g as shown in Fig. (2). It is clear from these figures that, t he imp ortance of using antireflection coating on both sides of substrate is t o get a high transmission and a minimum reflection. Experime nt The type and surface features of the substrate have a great influence on the p rop erties of the dep osition films into the substrate. In this work ZnSe substrate were used, the p olishin g machine and gr indin g for these substrates were performed by using a p olishing machine typ e TF-250 from (TEANWARTZ CO., Germany), and using diamond p astes with different smooth degrees (0.25, 1, 3, 9)µm for each smooth degree has a sp ecial p olishin g cloth. Then, these substrates were chemically clean ed as follows: 1- Using chemical solutions such as methanol then insert it in the ultrasonic dev ice for 15 min. 2- ZnSe were immersed in 2.5% HF then rinsed with demonized water and immersed in methanol, substrates where then dried with special smoothing p apers. The Al2O3 with p urity 99.999% was dep osited on both sides of Z nSe subst rates by using thermal evap oration machine ty p e (Varian). The film thickness was measured by cry stal monitoring which work with mech anical shut ter to stop the dep osition process when we reach the desired thickness. The thickness for each Al2O3 lay er was 195nm. IBN AL- HAITHAM J. FOR P URE & APPL. SCI VOL. 22 (3) 2009 The transmission for these ZnSe substrates without coating were measured b y using Fourier Transform Infrared (FT-IR) spectrophotometer as shown in Fig. (3). the maximum transmission was 72%. After that, these ZnSe substrates and high p urity Al2O3 material were placed in a vacuum coating machine having electron gun and operating voltage 6K V under vacuum of 10-5 mb ar. Results 1- The maximu m transmission was about 82% for ZnSe window after coating with eight lay ers of Al2O3 ARC's for one face of subst rate (thickness of each lay er = 195 nm) as shown in Fig.(4). 2- The transmission became 97% for these ZnSe subst rates after coating with eight layers of Al2O3 ARC's on both faces of the substrate as shown in Fig.(5). Conclusion From the p revious results it is p ossible to fabricate op tical window with maximum transmission of 97% by using eight lay ers of Al2O3 ARC's on both faces of ZnSe substrate. These results are in agreement with t he theoretical results deduced from (T F-CALC) program p ackage. Re ferences 1- M acleod, H.A., (1968),"Thin Film Op tical Filters", 2 nd ed. M cGraw- Hill Co., N.Y. 2- Bauer, G. (1934), "T hin Film Phenomena", Ann.Phys.Lbz. 5 th series 19: 434. 3- Knittl, Z. (1989), SPIE Proceeding, 401, 1. 4- Nagendra, C.L. and M ohan, S. (1989), Infra.Phy s. 2:29-195. 5- Grebenshchikov, I.V.; Vlasov, L.G. and Suikovskaya,N.V. (1946), Prosvtleny e Optiki, "Ant ireflection Coating of Opt ical Surfaces", State p ublishers of Technical and Theoretical Literature, M oscow, Leningr ad. 6- Abeles, F. (1990), Ann.D.Phy sique, 5: 596. 7- Herp in, J.D., (1987), "Op tical Thin Film: User Handbook", M cM illan, N.Y. 8- Epstein, L.I., (1992), J.Opt .Soc.Am. 42: 806. 9- Wellford , W.T., (1984), Vacuum, 4, 3. 10- Cox ,J.T . and Hass,G. (1988), J.Opt.Soc.Am., 48: 677. 11- Schuler, A.; Boudaden, J. and Scartz zini,J.L. (2005), Sol. Ener gy M ater. Sol. Cells, 89, 219. 12- Jacobs, S., (2000), SPIE p roceeding, 27, 196. 13- Chorp a, K.L., (1989), "Thin Film Phenomena", 3 ed ed., M cGraw – Hill Book Co., N.Y. IBN AL- HAITHAM J. FOR PU RE & APPL. SCI VOL.2 2 (3) 20 09 ٨٢ ٨٤ ٨٦ ٨٨ ٩٠ ٩٢ ٩٤ ٩٦ ٩٨ ١٠٠ ٤٠٠٠ ٤٥٠٠ ٥٠٠٠ ٥٥٠٠ ٦٠٠٠ Tr a n sm is si o n ( % ) Wavelength (nm) Fig. (2) the relation between transmittitance and wavelength for ZnSe with coating on both sides IBN AL- HAITHAM J. FOR PU RE & APPL. SCI VOL.2 2 (3) 20 09 ٠ ١٠ ٢٠ ٣٠ ٤٠ ٥٠ ٦٠ ٧٠ ٨٠ ٠ ١ ٢ ٣ ٤ ٥ ٦ ٧ Tr a n sm is si o n (% ) Wavelength (um) Fig.(3) Transmission spectrum for ZnSe substrate ٠ ١٠ ٢٠ ٣٠ ٤٠ ٥٠ ٦٠ ٧٠ ٨٠ ٩٠ ٠ ٢ ٤ ٦ ٨ Tr a n sm is si o n (% ) Wavelength (um) Fig. (4) Transmission spectrum for ZnSe substrate with antireflection coating (Al2O3)on one side ٠ ٢٠ ٤٠ ٦٠ ٨٠ ١٠٠ ١٢٠ ٠ ٢ ٤ ٦ ٨ Tr a n sm is si o n (% ) wavelength(um) Fig. (5) Transmission spe ctrum for ZnSe substrate with anti reflection coating (Al2O3) on both side