Nonlinear Optical Properties of PMMA Composites Using Z-Scan Technique

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1 Hussan M. H. et al., Iraqi J. Laser A, 2, (23) Iraqi J. Laser, Part A, Vol.2, pp (23) Nonlinear Optical Properties of Composites Using Z-Scan Technique Rusal M. Hussan Zainab F. Mahdi and Rawaa A. Faris Institute of laser for postgraduate studies, University of Baghdad, Baghdad, Iraq (Received 23 December 22; accepted 7 April 23) Abstract:The nonlinear refractive index and the nonlinear absorption coefficient of uodified and poly(methyl methacrylate) films were studied before and after the addition of the filler by the z-scan technique, using a Q-switched Nd:YAG laser at two wavelengths: 532 and 64, and at three input energies (3, 33 and 53). Both linear and nonlinear refractive indices and absorption coefficients of polymer films were studied by using UV-VIS spectrophotometer. The results show that the creation of from uodified will increase the nonlinear optical properties in the /copper matrix more than in the uodified /copper matrix. Hence, the appears promising as a useful third-order nonlinear material. The nonlinear refractive index is directly proportional to the input intensity and directly proportional to the increase in the concentration of the filler, while the nonlinear absorption coefficient is inversely proportional to the input energy and inversely proportional to the increase in the concentration of the filler. The nonlinear effect is more enhanced at the 532 wavelength than at 64.. Introduction There is considerable interest in finding materials having large yet fast nonlinearities. This interest, which is driven primarily by the search for materials for all-optical switching and sensor protection applications, concerns both nonlinear absorption (NLA) and nonlinear refraction (NLR). []. Amongst the nonlinear materials, organic polymers are particularly attractive because of its properties such as low density, mechanical flexibility and a high nonlinear response [2]. During the recent years, nonlinear optical properties have been the subject of numerous investigations theoretically and experimentally due to their applications [3]. Furlani et al. used symmetric and non-symmetrical Pt (II) and Pd (II) bisacetylides complexes and those dispersed in. Their nonlinear optical properties were measured using the z-scan technique with mode locked Ti-sapphire delivering pulse width of 5 fs with a wavelength of 77 [4]. Lee et al. reported the fabrication of gold- stacks and their linear and nonlinear optical properties [5]. Shettigar et al. studied the nonlinear optical parameters of bis_cholcone derivatives doped in matrix in a z-scan technique, by using 7ns Nd:YAG laser pulses at 532 wavelength[6]. Mathews et al. studied the nonlinear optical and optical limiting properties of tetra tertbutyl phthalocyanine and zinc tetra tert-butyl phthalocyanine at 633 wavelength using a continuous wave laser[7]. Shettigar et al. have investigated third-order nonlinear optical properties 3-phenyl sydones doped into and determined both real and 72

2 Hussan M. H. et al., Iraqi J. Laser A, 2, (23) imaginary parts of the third order nonlinear succeptibility, χ3 [2]. The z-scan technique is a relatively simple and direct method to characterize both the nonlinear refraction index and nonlinear absorption coefficient [8]. It is based on the nonlinear transverse modification of the laser beam throughout its focal length resulting in the intensity variation experienced by a sample which is moved along the propagation axis of the laser beam (z-axis) near the focal position [9]. When a small aperture is placed in front of the detector, it provides a measurement for the refractive index nonlinearity, while open aperture z-scan experiments are sensitive to the intensity dependent absorption coefficient []. The set-up of the z-scan system is shown in Figure Fig (): The setup of the z-scan system The experiment The poly (methyl methacrylate) supplied by BDH Chemicals LTD,England, with 99.8% purity, is used. The kind of filler used in this work, which is a copper ion source, was created from powder (from BDH Chemicals LTD, England), with 99.8% purity. Acetone was used as a solvent for, supplied by (BDH chemicals LTD England), with 99.9% purity. The uodified was created by dissolving.7 g of in ml acetone to get the homogenous solution. The magnetic heater stirrer was used as a source of heating and to mix the solution. The degree of heat must be less than the degree of its gl ss tr nsition temper ture g 5 C). The were synthesized from uodified by the base hydrolysis of the methacrylate groups in uodified to forming carboxylate groups in. This process is shown in the equation: () Where m,n are a number of moles. A copper ion was created by dissolving different weights of (.2,.4,.6,. and.4 g) in ml of acetone and stirred in magnetic stirrer without heating for hour [5]. After preparing uodified, the solution of acetone was added, then mixed using magnetic stirrer with heating the solution for 3 hours in order to avoid molecular aggregation. To get -: the acetone was added to, which is prepared as mentioned before, by using the magnetic stirrer. The uodified, and composite polymer solutions are pouring in a glass plate (2x7x5cm). To remove possible residual solvent, film samples were further dried at room temperature overnight. The atomic absorption/flame emission spectrophotometer (Shimadzu A.A 6 A) was used to calculate the amount of metal absorbed by the polymer and expressed in terms of mill equivalent per gram of polymer (m.eq.g -.) Optical techniques are used for measuring (linear and nonlinear properties) linear optical testing and nonlinear measurement. The Michelsons interferometer was used to measure the thickness of the s mples film. It w s found to be equ l to 5.3) μm. he thickness of the film equ ls 5.3 μm. Z-Scan measurements were performed in two parts, closed and open aperture. The closedaperture was used to measure the nonlinear refractive index, while the open-aperture was used to measure the nonlinear absorption coefficient. Each part was carried out withnd:yag at 64 and 532 using KTP crystal. [4,3,4]. Results and Discussion In the atomic absorption/flame emission spectrophotometer, the amount of Cu+2 from uodified and was measured. It was found to be equal to.58 (m.eq.g-) in uodified and.262 (m.eq.g -) in. Results showed that the capacity of ized for Cu+2 is larger than in uodified. This indicates the ability to bind Cu+2 ions. The ability is enhanced by base-catalyzed hydrolyses of methacrylate groups in uodified to format 72

3 Absorption Intensity Absorption Hussan M. H. et al., Iraqi J. Laser A, 2, (23) carboxylate groups. This is likely to increase the likelihood of precipitating inorganic particles within the polymer matrix [5]. UV-VIS absorption spectrum was obtained for uodified PMM after the addition of filler as shown in Figure 2. Fig. (2): UV-VIS absorption spectra of uodified after adding the filler The peak at 476 seems to correspond to the copper association. It is corresponding to a shift in the d-d transition of the copper due to the binding with polymer [5.] UV-VIS absorption spectrum for after the addition of filler is shown in Figure Wavelength () Wavelength () C ucl2.2h2o +.4 Fig. (3): The UV-VIS absorption spectra of after adding the filler The intensity of spectra is higher than the intensity of the uodified polymer spectra. The intensity of the peak is larger than the peak in uodified polymer. The same behavior can be seen for the peak position in, which means copper association. When is added, the peak at 476 seems to correspond to the copper association. Figure 4 represents a comparison in the absorbance at 476 as a function of copper concentration in both uodified and. Figure 4 represents a comparison in the absorbance at 476 as a function of copper concentration in both uodified and Concentration (M) UNMODIFIED FUNCTIONAL Fig. (4): The absorbance at 476 as a function of copper concentration in both uodified and It can be seen from Figure 4 that the absorbance for both polymers initially increases linearly with increasing copper concentration. It reaches a plateau, corresponding to reaching the binding capacity of the polymer for Cu+2 ions. The capacity of the ized polymer for Cu+2 is greater than uodified. This indicates that the ability to bind Cu+2 ions is enhanced by base-catalyzed hydrolysis of the ester groups to carboxylate groups. This behavior of absorption curves is in good agreement with the result reported by Lubeck [6].The nonlinear refractive index for uodified and was measured. Figure 5 shows the closed-aperture z-scan of uodified at 64 and 532 for 3, 33 and 53 72

4 n2 (cm2/gw) n2(cm2/gw) Hussan M. H. et al., Iraqi J. Laser A, 2, (23) at at at at at at uodified at uodified at 64.2 at at 64 Fluence(J/cm2) Fig. (5): The closed-aperture Z-scan of uodified The same behavior appears in,.2 M uodified and.2 M. (The same phenomenon appeared with in all the closed-aperture curves). In this mechanism, the maximum and minimum transmittance occurred at z equal to (5) mm and (-5) mm respectively. A peak followed by a valley at 64 and at 532 is the hallmark of a negative n2.the peak to valley profile, displayed in the figures, demonstrates that the sample exhibited a selfdefocusing effect. The nonlinear refractive index of uodified,,.2m uodified and.2m CuCl2.2H 2O in have been calculated from the variable transmittance values at two wavelengths, 532 and 64. The nonlinear refractive index depends on the energy and the wavelength of the laser. The behavior of n2 to the input fluence for uodified and at different energies at 532 and 64 can be shown in Figure 6, while the behavior of n2 to the input fluence for.2m uodified and at different energies at 532 and 64 can be shown in Figure Fluence (J/cm2) uodified at 532 uodified at 64 at 532 at 64 Fig. (6):The behavior of n 2 to the input fluence for uodified and Fig. (7): The behavior of n 2 to the input fluence for CuCl 2.2H 2 O in uodified and at.2 M concentration of CuCl 2.2H 2 O The nonlinear refractive index of the polymer thin films was affected by the addition of NaOH and different concentrations of filler. Figure 8 shows closed aperture measurement of uodified and with different concentration of at 532 at 3, while Figure 9 shows closed aperture measurement of uodified and with different concentrations of at 64 at Fig. (8): uodified and with different concentrations of CuCl 2.2H 2 O at 3 at uodified.2m in uodified.2m in.4m in uodified.4m in.6m in uodified.6m in uodified.2m in uodified.2m in.4m in uodified.4m in.6m in uodified.6m in Fig. (9): uodified and with different concentrations of at 3 at 64 3

5 n2(cm2/gw) n2(cm2/gw) Hussan M. H. et al., Iraqi J. Laser A, 2, (23) Figure represents the relation between nonlinear refractive index and the concentration of the filler at 532, and Figure shows the relation between nonlinear refractive index and the concentration of the filler at 64 as shown below CONCENTRATION (M) Uodified at 3 AT 3 MJ Uodified at 33 mj at 33 UNMODIFIED at 53 L AT 53 Fig. (): represents the relation between n 2 and different concentrations in both uodified and at Uodified at 3 AT 3 MJ Uodified at 33 mj at 33 refractive indices will cause will cause scattering of the light and increasing absorbance of the light by the new group. The refractive index will be less than in uodified [7]. The same behavior can be seen in the wavelengths 532 and 64. Adding to both uodified and, the magnitude of n2 is larger than when adding the filler to the polymer thin films. The result is due to the. This material absorbs visible light [8]. All these reasons will cause the refractive index to decrease with the addition of to the uodified and [8]. The magnitude n2 started with a small increase at low concentration. At a higher concentration, the value of n2 increased very strongly in both and uodified when adding at (532) and (64). In -, the magnitude of n2 is larger than in uodified - at the same concentration of, with the same wavelength and at the same energy, because the capacity of the ized polymer for Cu+2 is greater than uodified. The magnitude of n2 is increased with the increasing of the concentration of for the two polymers ( and uodified.) The effect of nonlinear absorption in uodified is shown in Figure 2 at different energies. In, the behavior of transmittance as a function of sample position a long z-scan can be investigated from Figure 3 at different energies UNMODIFIED at 53 L AT at at CONCENTRATION (M).6 33 at 532 Fig. (): shows the relation between n 2 and different concentrations in both uodified and at 64 The refractive index in is smaller than in uodified in both wavelengths of 532 and 64. The addition of NaOH to uodified caused a change in the refractive index. So the presence of overlapping between regions of different at at at 64 Fig. (2): The open-aperture Z-scan of uodified 3

6 β(cm/gw) β (cm/gw) Hussan M. H. et al., Iraqi J. Laser A, 2, (23) at at at at at at 64 Fig. (3): The open-aperture z-scan of Figure 4 and Figure 5 represents the open aperture for uodified and with.2m concentration of the change in intensity is caused by two-photon absorption. In uodified and with at 3 and 33, the change in intensity is caused by saturable absorption. Increasing energy to 53, the sample starts showing two-photon absorption.the beh vior of β to the input fluence for uodified and at different energies, at 532 and 64 can be shown in Figure 6, but Figure 7 shows the beh vior of β to the input fluence for. 2M uodified and at different energies, at 532 and uodified at 532 uodified at at at at at at at Fig. (6): the relation between fluence and and uodified 6 5 Fluence (J/cm2) at 532 at 64 β in.2m in uodified at 532 Fig. (4): The open-aperture Z-scan of.2m CuCl 2.2H 2 O in uodified 4 3.2M in uodified at at at at at at at 64 Fig. (5): The open-aperture Z-scan of.2m CuCl 2.2H 2 O in The transmittance is sensitive to the nonlinear absorption as a function of input energy pulses. In uodified and, fluence(j/cm2).2m in at 532.2M in at 64 Fig. (7): the relation between fluence and β in and uodified with.2m CuCl 2.2H 2 O At 64, the m gnitude of β is independent of the intensity. This property is more enhanced t 532, so the m gnitude of β t 532 is larger than at 64, which means that the nonlinear effect is increased at the focal point at wavelength 532 more than in 64. The m gnitude of β is decre sed with the incre se in fluence, which means the nonlinear absorption 7

7 Hussan M. H. et al., Iraqi J. Laser A, 2, (23) coefficient β is inversely proportion l to the input energy. The nonlinear absorption coefficient of the polymer thin films was affected by the addition of NaOH and different concentration of filler. Figure 8 shows the behavior of open aperture of uodified and with different concentrations of at 532 and uodified.2m uodified uodified.2m uodified.2m.4m uodified.4m.6m uodified.6m Fig. (8): open aperture of uodified and at 532 and 3 The same behavior was obtained for open aperture at 33 and at 532. Open aperture at 532 and at 53 of uodified and with different concentration of can be investigated in Figure M.4M uodified.4m uodified.6m UNMODIFIED.6M CuCl2.2H2 in uodified.2m in uodified.2m in.4m in uodified.4m in.6m in uodified.6m in Fig. (9): open aperture of uodified and at 532 and 53 At 64, the behavior of open aperture of uodified and with different concentrations of at 3 is represented in Figure 2. Fig. (2): open aperture of uodified and at 64 and 3 The same behavior of open aperture appeared at 33 and at 532. Figure2 summarizes the behavior of open aperture of uodified and with different concentrations of at 64 and uodified.2 in uodified.2m in.4m in uodified.4m in.6m in.6m in Fig. (2): open aperture of uodified and at 64 and 53 Figure 22 summ rizes the rel tion between β and different concentrations in both uodified and when adding different concentrations of at 532, while the rel tion between β nd different concentrations in both uodified and when adding different concentrations of at 64 is shown in Figure 23.

8 β (cm/gw) β(cm/gw) Hussan M. H. et al., Iraqi J. Laser A, 2, (23) Fig. (22): The relation between the concentration of CuCl 2.2H 2 O and β at Concentration (M) Concentration (M) uodified at 3 at 3 uodified at 33 at 33 uodified at 52.5 at 52.5 uodified at 3 at 3 uodified at 33 at 33 uodified at 52.5 at 52.5 Mj Fig. (23): The relation between the concentration of CuCl 2.2H 2 O and β at 64 The absorption coefficient in is higher than in uodified for both wavelengths, at 532 and 64. The m gnitude β is inversely proportion l to the concentration of the filler in both and uodified. In -, the m gnitude of β is l rger th n in uodified - at the same concentration of, at the same wavelength and at the same energy, because the capacity of the ized polymer for Cu+2 is greater than uodified. Before adding to both uodified and function l, the m gnitude of β is sm ller than after adding the filler to the polymer thin films. Conclusions The capacity of ized for Cu+2 is greater than uodified, and the creation of from uodified will increase the nonlinear optical properties in /copper matrix more than in uodified /copper matrix. Hence, the appears promising as a useful third-order nonlinear material. The nonlinear refractive index is directly proportional to the input intensity and directly proportional to the increase in the concentration of the filler. While the nonlinear absorption coefficient is inversely proportional to the input energy and inversely proportional to the increase in the concentration of the filler. The nonlinear absorption coefficient in uodified and is caused by the effect of two photon absorption. When the copper (II) chloride dehydrate is added to the polymer matrix, the nonlinear absorption coefficient at the low intensity is caused by the saturable absorption, while at high intensity it is caused by two photon absorption. The nonlinear effect is more enhanced at the wavelength 532 than at 64. References []E. W. VanStryland andm. Sheik-Bahae:Z- Scan Measurements of Optical Nonlinearities,Characterization Techniques and Tabulations for Organic Nonlinear Materials, p , Marcel Dekker, Inc., 998 [2] S. Shettigar, G.Umesh, K. Chandarasekharun, B. Kallurya: Synthetic Metals, 57, (27). [3]C.S.Winter, R.J.Manning, S.N.Oliver and C.A.S.Hill: Optics Communications, 9, (992). [4]A.Furlani, M.Colopietro, G.Portalone, R.D. Amato,M.Casalboni, M.Falconieri and M.V. Russo, J. Organometallic Chemistry, 627, 3-22 (2). [5]T.K.Lee, D.Bristow, J.Hubner and H.M.Vandriel, Optical Society of America (26). [6]S.Shettigar, G.Umesh, K.Chandrasckharan, and B.Kalluraya: Synthetic Metals, 47, (26). [7]S.J.Mathews, J.C.Kumar, L.Giribabu and S.V.Pao: Material letters (27). 3

9 Hussan M. H. et al., Iraqi J. Laser A, 2, (23) [8] M.Sheik-Bahae, A.A.Said, M.J.Soileau and S.E.W.Van Styralnd, Optical Engineers,3,No. 8 (99). [9] T. Wang, M. SheirkBahae, A.A. Said, D.J. Hagan and E.W. Van Stryland, IEEE Journal of Quantum Electronics, 26, No.4, , (99).] [] C.S.Winter, R.J.Manning, S.N.Oliver and C.A.S.Hill: Optics Communications, 9, (992). [] S.Ma, S.Wang, J. Zheng, M.Xu and Y.Li: Optics Communications,49,8-2, (998). [2] J. Keprt and L. Bartonìk:Physica, 39, 39-59, (2). [3] M.S.Bahae, D.J.Hagan, IEEE J. Quantum Electronics 26, 4 (996). [4] D.O.Altaify and Z.F.Mahdi, Iraqi Journal of Laser, nonlinear optical properties of cds thin film nanoparticles using z-scantechnique,27. [5] J.A.Brydson, "Plastic Materials,"7 th ed., Butterworth Heinemenann, New Delhi (999). [6] C.R. Lubeck, M.C.Chin, and F.M. Doyle, Materials Science and Engineering,85, (23). [7] G.Odiam, "Principles of Polymerization," 4 th ed, John Wile andsons,inc., New Jersey (24). [8] L.G. Carotenuto, "Metal Polymer Nanocomposite," Wiley Interscience publication, New Jersey (24) دراسة الصفات البصر ة الالخط ة لمحراكبات البىل مث ل م ثا اكر لث بأسحخذام جقن ة المسح على المحىر الثالث رسل محمذ حسن ز نب فاضل مهذي رواء احمذ فارس عهذ اىييشر ىيذراساث اىعييا, جا عت بغذاد, اىعزاق الخالصة : ح دراست عا و اال نسار اىالخطي و عا و اال خصاص اىالخطي ألغشيت اىبىىي زيو يزا امزييج اى حىر وقبو اىخحىيز بأضافت اىيء بأسخخذا حق يت اى سح عيى اى حىر اىزاىذ بأسخخذا ىيشر اى ذي يى ياك اى بضي ع ذ طىىي ىجيي 333 و 37 ا ى خز. وىزالد طاقاث ىيشريت, 3, و 3 يي جىه. ومذىل ح ايجاد عا و اال نسار و عا و اال خصاص اىخطي بأسخخذا جهاس اى طياف. اى خائج اظهزث ا اىبىىي ز اى حىر واى نى بأضافت اىيء حشداد فيه ااىصفاث اىبصزيت اىالخطيت ظهىرا ع سيادة سبت اى اىيء وهى اى حاص. وبذىل فأ اى خزامب اىفعاه اظهز ا نا يت اسخخذا ه م ادة الخطيت. ووجذ ايضا أ عا و اال نسار اىالخطي يخ اسب طزديا ع اىشذة اىييشريت و ع اىشيادة في حزميش اى اىيء,بي ا باى سبت ى عا و اال خصاص اىالخطي فأ ه يخ اسب عنسيا ع اىشيادة في حزميش اى اىيء. اىخأريز اىالخطي يشداد ع ذ اىطىه اى ىجي 37 ا ى خز امزز ه ع ذ اىطىه اى ىجي 333 ا ى خز. 3