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Optical limiting behavior of Sudan III dye doped polymer
ARTICLE IN PRESS Optics & Laser Technology 42 (2010) 531–533
Contents lists available at ScienceDirect
Optics & Laser Technology journal homepage: www.elsevier.com/locate/optlastec
Optical limiting behavior of Sudan III dye doped polymer M.D. Zidan , A.W. Allaf, Z. Ajji, A. Allahham Department of Physics, Atomic Energy Commission, PO Box 6091, Damascus, Syria
a r t i c l e in fo
abstract
Article history: Received 25 February 2009 Received in revised form 16 April 2009 Accepted 29 September 2009 Available online 27 October 2009
The optical limiting performance of Sudan III dye doped into ethylene propylene diene polymethylene polymer (EPDM) is investigated using 532 nm, 10 ns pulses from a frequency-doubled Nd–YAG laser. The optical limiting behavior is investigated by transmission measurement through the sample at different concentrations. Our results show that the optical limiting efficiency is concentration dependent. & 2009 Elsevier Ltd. All rights reserved.
PACS: 42.65.Ky 42.70.Nq 42.70.jk 84.30.Qi Keywords: Nonlinear absorption Optical limiting Sudan III dye
1. Introduction With the development of laser technology, much interest in the development of optical limiting materials has been made among researches working on materials. Devices for human eye protection and solid-state sensors from intense laser beams are sought [1–3]. Previous researches on optical limiting materials were focused on nonlinear, organic [4,5] and semiconductor materials [6]. Since it was found that organic materials have large nonlinearity and ultra-fast response time [4], the research on optical limiting organic materials is of great importance [5]. Nonlinear absorptive organic dyes are among the most widely studied optical limiting materials [6]. Recently, Palanisamy et al. studied the third-order nonlinear optical response of a triphenylmethane dye (Acid blue 7) using the Z-scan technique with a continuous-wave He–Ne laser radiation at 633 nm [7]. The nonlinear responses and optical limiting performance of a dye-type acid, called fast green FCF, are investigated under irradiation of 35 mW continuous-wave He–Ne laser [8]. The nonlinear optical absorption, refraction and optical limiting behavior of an organic dye, neutral red, were investigated under excitation with nanosecond laser pulses at 532 nm [9]. The third-order nonlinear optical properties and the optical power limiting behavior of
Corresponding author. Tel.: + 963 11 2132580; fax: + 963 11 6112289.
E-mail address: scientifi[email protected] (M.D. Zidan). 0030-3992/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2009.09.012
3-phenyl sydnones doped PMMA were investigated by using nanosecond Nd–YAG laser pulses at 532 nm wavelength [10]. It is well known that concentration dependence plays a very important role in the optical limiting action. The optical limiting effect is enhanced and the transmittance decreased with increase in concentration. This is because a sample with high concentration has more molecules per unit volume participating in the interaction during nonlinear absorption. However, the concentration of the sample should be chosen carefully. When the concentration is too high, the result is very poor transmission, while at low concentration the optical limiting effect may disappear. Thus the concentration threshold is very important in optical limiting investigations. Several groups have studied the effect of concentration on the optical limiting behavior of organic dye molecules. The optical limiting performances of copper phthalocyanine and polychlorocopper phthalocyanine have been investigated using 1064 nm continuous wave laser. The output–input power characteristics and nonlinear transmission properties for different solutions of copper phthalocyanine and polychlorocopper phthalocyanine in acetone at increasing concentrations were obtained. The good optical limiting performance is attributed to a reverse saturable absorption (RSA) mechanism [11]. Also, the optical limiting behavior of zinc phthalocyanines in toluene solution and in polymeric matrix was investigated at different concentrations [12]. Their preliminary study was crucial for the realization of films with the maximum allowed concentration of Zn–Pc, since the efficiency of the nonlinear absorption process
ARTICLE IN PRESS M.D. Zidan et al. / Optics & Laser Technology 42 (2010) 531–533
is directly proportional to the concentration of nonlinear molecules. The effect of concentration on nonlinear properties of p-(N,N-dimethylamino) dibenzylideneaceton doped PMMA has been reported [13] by using Nd–YAG laser, 7 ns laser pulses at 532 nm. The nonlinear absorption in the dyes is due to the dependence of reverse saturable absorption (RSA), two-photon absorption (TPA) and saturable absorption (SA) on the change in absorption (increase or decrease) with increased intensity. Both TPA and RSA lead to increase in absorption in the sample with increase in intensity [9]. For a given organic sample at a fixed wavelength, either TPA or RSA is the dominant mechanism leading to increase in absorption with intensity. RSA is observed when the excited state absorption (ESA) is greater than the ground state absorption, which results in decrease in the transmission through the medium with increase in the input intensity. ESA and RSA are the most common mechanisms for the nonlinear optical limiting behavior of organic materials [14,15]. This paper presents the results of our investigations on the optical limiting behavior of Sudan III dye doped into EPDM polymer with four different concentrations, using 532 nm, 10 ns pulses from a frequency-doubled Nd–YAG laser.
2. Experimental technique The Sudan III dye was purchased from Aldrich and used without any purification. Fig. 1. shows the molecular structure of Sudan III dye. Since, the dye cannot be directly used in practical devices in powder form, one can overcome this problem and make effective use of this material in devices by doping the dye molecules into a polymer matrix, as this can enhance the optochemical and opto-physical stability as well as mechanical and thermal properties, while retaining the NLO properties and linear optical transparency. Sampling preparation was carried out as follows A solvent mixture of 3:1 toluene:ether was prepared, and the EPDM polymer (EPDM Vistalon 7500 with an ethylene content is 55.5% in wt from Exxon Mobil Chemicals) was dissolved in this solvent mixture (1 g EPDM to 25 ml solvent). Then the Sudan III was also dissolved in solvent mixture and different amounts of this solution were added to a constant volume of the EPDM solutions mixture. The following dye/polymer samples concentrations were at 0.1, 0.2, 0.3, 0.4 and 0.6 mg/g. Certain volumes of the different sample solutions were cast onto a polyester sheet, which is fixed on a glass plate in order to achieve a desired thickness of
Iris
Sample
Beam splitter Nd-YAG laser
Lens
Attenuator
Power meter 2
Power meter 1 Fig. 2. Experimental set-up for optical limiting measurements of Sudan III dye doped into EPDM polymer.
1.5
1.2
Absorbance
532
0.9
0.6
0.3
0.0 300
400
500
600 700 800 Wavelength [nm]
900
1000
1100
Fig. 3. The UV–Vis absorption spectrum of Sudan III dye doped EPDM polymer at a concentration of 0.3 mg/g.
the polymer film. The samples were dried in an oven at 60 1C in order to evaporate the solvents. Optical limiting measurements were performed using the setup illustrated in Fig. 2. The measurements were done with a frequency-doubled Nd–YAG laser system. The laser output was varied in the range 5–300 mJ by adjusting the delay time of the Q-switch from its optimal setting. The laser pulses of 10 ns and 1 Hz repetition rate were guided onto the sample through a lens with 100 mm focal length. In order to avoid damaging of the sample, it is located out of the focus point; the radius of the laser beam at the sample was approximately 250 mmin ,1/e2 diameter. In order to avoid cumulative thermal effects, data were collected in the single shot mode. The experiments were performed at room temperature. The incident and the transmitted energies were measured simultaneously by two pyroelectric detectors with Lab-Master Ultima Coherent energy/power meter. 3. Results and discussions
Fig. 1. Molecular structure of SUDAN III dye (C22H16N4O).
The UV–visible absorption spectrum of Sudan III dye doped into EPDM polymer was recorded using a UV-3101 PC Shimadzo Spectrophotometer. The optical absorption of the Sudan III doped EPDM dissolved in toluene and DMF with concentration 0.3 mg/g shows an absorption peak at 510 nm as shown in Fig. 3. Fig. 4 shows the typical results of the optical limiting behavior in Sudan III dye doped into EPDM polymer for different concentrations (0.2, 0.3, 0.4 and 0.6 mg/g). Optical limiting
ARTICLE IN PRESS M.D. Zidan et al. / Optics & Laser Technology 42 (2010) 531–533
Output Fluence (J/cm2)
T = %45
0.2 mg/g 0.3 mg/g 0.4 mg/g 0.6 mg/g
20
15
T = %30
10
T = %20
5
have been proposed for the explanation of the optical limiting behavior in organic dyes including RSA, nonlinear scattering, and multiphoton absorption. But the RSA mechanism, by a 5-level energy diagram, yielded a reasonable explanation for optical limiting in the conjugated organic systems [6,11,16,17]. The calculated values of linear absorption coefficient (a), linear transmission (%T) and the optical limiting threshold (Eth) for all sample concentrations are shown in Table 1. Finally, absorption spectra of the sample were acquired before and after the laser irradiation and it was found that the pattern and its intensity have almost no change, indicating that the prepared sample processes photostability.
4. Conclusions
0 0
5
10
15 20 25 30 35 Input Fluence (J/cm2)
40
45
50
Fig. 4. Variation in output fluence with input fluence through the Sudan III doped into EPDM polymer at different concentrations 0.2, 0.3, 0.4 and 0.6 mg/g.
Table 1 Summarizes the calculated values of linear absorption coefficient (a), linear transmission (%T), and the optical limiting threshold at four concentrations. Sample concentrations (mg/g) 0.2 0.3 0.4 0.6
533
Linear absorption coefficient a (mm
0.17 0.17 0.26 0.35
1
)
Linear transmission (%T)
Optical Limiting threshold Eth (J/cm2)
45 45 30 20
12 10 9 5
behavior was obtained by varying the input energy as shown in Fig. 4. As it is shown clearly at low incident energy, the output energy varies linearly with input energy and the transmittance obeyed Beer’s law: I= I0e al, where I, I0, a and l are the incident energy, the output energy, the absorption coefficient and the sample path length, respectively. In the same figure, the deviations from linearity began at 12, 10, 9 and 5 J/cm2 at 0.2, 0.3, 0.4 and 0.6 mg/g concentrations, respectively. At high concentration (0.6 mg/g) the output fluence starts to exhibit clamping with low input fluence. It should be mentioned here that similar results were observed at both concentrations (0.1 and 0.2 mg/g); also at concentrations higher than 0.6 mg/g, the output transmittance was very low and it was not possible to be recorded. Therefore, Fig. 4 shows only four different concentrations at 0.2, 0.3, 0.4 and 0.6 mg/g. It is well known that the optical limiting responses of the low-concentration solution are generally much weaker than those of more-concentrated solutions While highconcentrated solution exhibits strong optical limiting, it indicates that a sample with a high concentration has more molecules per unit volume to contribute to the nonlinear absorption processes. From the threshold intensity for optical limiting for each sample, it can be noticed that the threshold is inversely proportional to the concentration. Also, the data show that as the concentration increases, a reduction in linear transmittance as well as the clamping level is observed. The observed results confirm previous findings that the concentration effect is remarkable [13–15]. Our results show that the absorption coefficient of the sample increased with increase in incident laser intensity. Therefore, we can say that the optical limiting behavior of the Sudan III dye doped into EPDM polymer, corresponding to 10 ns pulses, originated from reverse saturable absorption (RAS). However, several mechanisms
We have presented the measurement results of the optical limiting performance in the Sudan III dye doped into EPDM polymer at 0.2, 0.3, 0.4 and 0.6 mg/g concentrations, using 532 nm, 10 ns pulses from a frequency-doubled Nd–YAG laser. These studies reveal that Sudan III dye can be a promising dopant material and hence can be used in optical limiting applications.
Acknowledgements The authors would like to thank Prof. I. Othman, the General Director, for his encouragement and support.
References [1] Bunning TJ, Natarajan IV, Schmitt MG, Epling BL, Crane RL. Nonlinear optical properties of poylaniline composite materials. Applied Optics 1991;30:4341–9. [2] Tutt LW, Kost A. Optical limiting performance of C60 and C70 solutions. Nature 1992;356:225–6. [3] Chari R, Mishra SR, Rawat HR, Oak SM. Reverse saturable absorption and optical limiting in indanthrone dyes. Applied Physics B 1996;62:293–7. [4] Wang H, Xu J, Yu C. SPIE2321 1994, p.10. [5] Bunning TJ, Natamian LV. Optics Letters 1990;15:700. [6] Sun Ya-Ping, Riggs JE. Organic and inorganic optical limiting materials from fullerenes and nanoparticles. International Reviews in Physical Chemistry 1999;18:43–90. [7] Geethakrishnan T, Palanisamy PK. Z-scan determination of the third-order optical nonlinearity of a triphenylmethane dye using 633 nm He–Ne laser. Optics Communications 2007;270:424–8. [8] Jamshidi-Ghaleh K, Salmani S, Majles Ara MH. Nonlinear responses and optical limiting behavior of fast green FCF dye under a low power CW He–Ne laser irradiation. Optics Communications 2007;271:551–4. [9] George M, Muneer CI, Singh CP, Bindra KS, Oak SM. Z-scan studies and optical limiting of nanosecond laser pulses in neutral red dye. Optics & Laser Technology 2008;40:373–8. [10] Shettigar Seetharam, Umesh G, Chandrasekharan K, Kalluraya Balakrishna. Third-order nonlinear optical properties and two photon absorption in newly synthesized phenyl sydnone doped polymer. Synthetic Metals 2007;157:142–6. [11] Fang Li, Zheng Qiguang, Yang Guang, Dai Nengli, Lu Peixiang. Optical limiting properties of two phthalocyanines using 1064 nm laser in solution. Materials Letters 2008;62:3059–62. [12] Ostuni R, Larciprete MC, Leahu G, Belardini A, Sibilia C, Bertolotti M. Optical limiting behavior of zinc phthalocyanines in polymeric matrix. Journal of Applied Physics 2007;101:033111–6. [13] John Kiran, Nooji Satheesh Rai, Udayakumar D, Chandrasekharan K, Kalluraya B, Philip Reji, et al. Nonlinear optical properties of p-(N,N-dimethylamino) dibenzylideneacetone doped polymer. Materials Research Bulletin 2008;43: 707–13. [14] Riggs JE, Sun Ya-Ping. Optical limiting properties of [60]fullerene and methano[60]fullerene derivative in solution versus in polymer matrix: the role of bimolecular processes and a consistent nonlinear absorption mechanism. Journal of Physical Chemistry A 1999;103:485–95. [15] Harilal SS, Bindhu CV, Nampoori VPN, Vallabhan PG. Optical limiting and thermal lensing studies in C60. Journal of Applied Phyiscs 1999;86(3):1388–92. [16] Hongyao Xu, Jiang Minhua, Song Yinglin, Chunfei Li. Optical limiting of a new substituted polydiacetlene. Materials Letters 1996;27:91–4. [17] Tong R, Wuc H, Lia B, Zhua R, Youa G, Qian Sh, et al. Reverse saturable absorption and optical limiting performance of fullerene-functionalized polycarbonates in femtosecond time scale. Physica B 2005;366:192–9.
Contents lists available at ScienceDirect
Optics & Laser Technology journal homepage: www.elsevier.com/locate/optlastec
Optical limiting behavior of Sudan III dye doped polymer M.D. Zidan , A.W. Allaf, Z. Ajji, A. Allahham Department of Physics, Atomic Energy Commission, PO Box 6091, Damascus, Syria
a r t i c l e in fo
abstract
Article history: Received 25 February 2009 Received in revised form 16 April 2009 Accepted 29 September 2009 Available online 27 October 2009
The optical limiting performance of Sudan III dye doped into ethylene propylene diene polymethylene polymer (EPDM) is investigated using 532 nm, 10 ns pulses from a frequency-doubled Nd–YAG laser. The optical limiting behavior is investigated by transmission measurement through the sample at different concentrations. Our results show that the optical limiting efficiency is concentration dependent. & 2009 Elsevier Ltd. All rights reserved.
PACS: 42.65.Ky 42.70.Nq 42.70.jk 84.30.Qi Keywords: Nonlinear absorption Optical limiting Sudan III dye
1. Introduction With the development of laser technology, much interest in the development of optical limiting materials has been made among researches working on materials. Devices for human eye protection and solid-state sensors from intense laser beams are sought [1–3]. Previous researches on optical limiting materials were focused on nonlinear, organic [4,5] and semiconductor materials [6]. Since it was found that organic materials have large nonlinearity and ultra-fast response time [4], the research on optical limiting organic materials is of great importance [5]. Nonlinear absorptive organic dyes are among the most widely studied optical limiting materials [6]. Recently, Palanisamy et al. studied the third-order nonlinear optical response of a triphenylmethane dye (Acid blue 7) using the Z-scan technique with a continuous-wave He–Ne laser radiation at 633 nm [7]. The nonlinear responses and optical limiting performance of a dye-type acid, called fast green FCF, are investigated under irradiation of 35 mW continuous-wave He–Ne laser [8]. The nonlinear optical absorption, refraction and optical limiting behavior of an organic dye, neutral red, were investigated under excitation with nanosecond laser pulses at 532 nm [9]. The third-order nonlinear optical properties and the optical power limiting behavior of
Corresponding author. Tel.: + 963 11 2132580; fax: + 963 11 6112289.
E-mail address: scientifi[email protected] (M.D. Zidan). 0030-3992/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2009.09.012
3-phenyl sydnones doped PMMA were investigated by using nanosecond Nd–YAG laser pulses at 532 nm wavelength [10]. It is well known that concentration dependence plays a very important role in the optical limiting action. The optical limiting effect is enhanced and the transmittance decreased with increase in concentration. This is because a sample with high concentration has more molecules per unit volume participating in the interaction during nonlinear absorption. However, the concentration of the sample should be chosen carefully. When the concentration is too high, the result is very poor transmission, while at low concentration the optical limiting effect may disappear. Thus the concentration threshold is very important in optical limiting investigations. Several groups have studied the effect of concentration on the optical limiting behavior of organic dye molecules. The optical limiting performances of copper phthalocyanine and polychlorocopper phthalocyanine have been investigated using 1064 nm continuous wave laser. The output–input power characteristics and nonlinear transmission properties for different solutions of copper phthalocyanine and polychlorocopper phthalocyanine in acetone at increasing concentrations were obtained. The good optical limiting performance is attributed to a reverse saturable absorption (RSA) mechanism [11]. Also, the optical limiting behavior of zinc phthalocyanines in toluene solution and in polymeric matrix was investigated at different concentrations [12]. Their preliminary study was crucial for the realization of films with the maximum allowed concentration of Zn–Pc, since the efficiency of the nonlinear absorption process
ARTICLE IN PRESS M.D. Zidan et al. / Optics & Laser Technology 42 (2010) 531–533
is directly proportional to the concentration of nonlinear molecules. The effect of concentration on nonlinear properties of p-(N,N-dimethylamino) dibenzylideneaceton doped PMMA has been reported [13] by using Nd–YAG laser, 7 ns laser pulses at 532 nm. The nonlinear absorption in the dyes is due to the dependence of reverse saturable absorption (RSA), two-photon absorption (TPA) and saturable absorption (SA) on the change in absorption (increase or decrease) with increased intensity. Both TPA and RSA lead to increase in absorption in the sample with increase in intensity [9]. For a given organic sample at a fixed wavelength, either TPA or RSA is the dominant mechanism leading to increase in absorption with intensity. RSA is observed when the excited state absorption (ESA) is greater than the ground state absorption, which results in decrease in the transmission through the medium with increase in the input intensity. ESA and RSA are the most common mechanisms for the nonlinear optical limiting behavior of organic materials [14,15]. This paper presents the results of our investigations on the optical limiting behavior of Sudan III dye doped into EPDM polymer with four different concentrations, using 532 nm, 10 ns pulses from a frequency-doubled Nd–YAG laser.
2. Experimental technique The Sudan III dye was purchased from Aldrich and used without any purification. Fig. 1. shows the molecular structure of Sudan III dye. Since, the dye cannot be directly used in practical devices in powder form, one can overcome this problem and make effective use of this material in devices by doping the dye molecules into a polymer matrix, as this can enhance the optochemical and opto-physical stability as well as mechanical and thermal properties, while retaining the NLO properties and linear optical transparency. Sampling preparation was carried out as follows A solvent mixture of 3:1 toluene:ether was prepared, and the EPDM polymer (EPDM Vistalon 7500 with an ethylene content is 55.5% in wt from Exxon Mobil Chemicals) was dissolved in this solvent mixture (1 g EPDM to 25 ml solvent). Then the Sudan III was also dissolved in solvent mixture and different amounts of this solution were added to a constant volume of the EPDM solutions mixture. The following dye/polymer samples concentrations were at 0.1, 0.2, 0.3, 0.4 and 0.6 mg/g. Certain volumes of the different sample solutions were cast onto a polyester sheet, which is fixed on a glass plate in order to achieve a desired thickness of
Iris
Sample
Beam splitter Nd-YAG laser
Lens
Attenuator
Power meter 2
Power meter 1 Fig. 2. Experimental set-up for optical limiting measurements of Sudan III dye doped into EPDM polymer.
1.5
1.2
Absorbance
532
0.9
0.6
0.3
0.0 300
400
500
600 700 800 Wavelength [nm]
900
1000
1100
Fig. 3. The UV–Vis absorption spectrum of Sudan III dye doped EPDM polymer at a concentration of 0.3 mg/g.
the polymer film. The samples were dried in an oven at 60 1C in order to evaporate the solvents. Optical limiting measurements were performed using the setup illustrated in Fig. 2. The measurements were done with a frequency-doubled Nd–YAG laser system. The laser output was varied in the range 5–300 mJ by adjusting the delay time of the Q-switch from its optimal setting. The laser pulses of 10 ns and 1 Hz repetition rate were guided onto the sample through a lens with 100 mm focal length. In order to avoid damaging of the sample, it is located out of the focus point; the radius of the laser beam at the sample was approximately 250 mmin ,1/e2 diameter. In order to avoid cumulative thermal effects, data were collected in the single shot mode. The experiments were performed at room temperature. The incident and the transmitted energies were measured simultaneously by two pyroelectric detectors with Lab-Master Ultima Coherent energy/power meter. 3. Results and discussions
Fig. 1. Molecular structure of SUDAN III dye (C22H16N4O).
The UV–visible absorption spectrum of Sudan III dye doped into EPDM polymer was recorded using a UV-3101 PC Shimadzo Spectrophotometer. The optical absorption of the Sudan III doped EPDM dissolved in toluene and DMF with concentration 0.3 mg/g shows an absorption peak at 510 nm as shown in Fig. 3. Fig. 4 shows the typical results of the optical limiting behavior in Sudan III dye doped into EPDM polymer for different concentrations (0.2, 0.3, 0.4 and 0.6 mg/g). Optical limiting
ARTICLE IN PRESS M.D. Zidan et al. / Optics & Laser Technology 42 (2010) 531–533
Output Fluence (J/cm2)
T = %45
0.2 mg/g 0.3 mg/g 0.4 mg/g 0.6 mg/g
20
15
T = %30
10
T = %20
5
have been proposed for the explanation of the optical limiting behavior in organic dyes including RSA, nonlinear scattering, and multiphoton absorption. But the RSA mechanism, by a 5-level energy diagram, yielded a reasonable explanation for optical limiting in the conjugated organic systems [6,11,16,17]. The calculated values of linear absorption coefficient (a), linear transmission (%T) and the optical limiting threshold (Eth) for all sample concentrations are shown in Table 1. Finally, absorption spectra of the sample were acquired before and after the laser irradiation and it was found that the pattern and its intensity have almost no change, indicating that the prepared sample processes photostability.
4. Conclusions
0 0
5
10
15 20 25 30 35 Input Fluence (J/cm2)
40
45
50
Fig. 4. Variation in output fluence with input fluence through the Sudan III doped into EPDM polymer at different concentrations 0.2, 0.3, 0.4 and 0.6 mg/g.
Table 1 Summarizes the calculated values of linear absorption coefficient (a), linear transmission (%T), and the optical limiting threshold at four concentrations. Sample concentrations (mg/g) 0.2 0.3 0.4 0.6
533
Linear absorption coefficient a (mm
0.17 0.17 0.26 0.35
1
)
Linear transmission (%T)
Optical Limiting threshold Eth (J/cm2)
45 45 30 20
12 10 9 5
behavior was obtained by varying the input energy as shown in Fig. 4. As it is shown clearly at low incident energy, the output energy varies linearly with input energy and the transmittance obeyed Beer’s law: I= I0e al, where I, I0, a and l are the incident energy, the output energy, the absorption coefficient and the sample path length, respectively. In the same figure, the deviations from linearity began at 12, 10, 9 and 5 J/cm2 at 0.2, 0.3, 0.4 and 0.6 mg/g concentrations, respectively. At high concentration (0.6 mg/g) the output fluence starts to exhibit clamping with low input fluence. It should be mentioned here that similar results were observed at both concentrations (0.1 and 0.2 mg/g); also at concentrations higher than 0.6 mg/g, the output transmittance was very low and it was not possible to be recorded. Therefore, Fig. 4 shows only four different concentrations at 0.2, 0.3, 0.4 and 0.6 mg/g. It is well known that the optical limiting responses of the low-concentration solution are generally much weaker than those of more-concentrated solutions While highconcentrated solution exhibits strong optical limiting, it indicates that a sample with a high concentration has more molecules per unit volume to contribute to the nonlinear absorption processes. From the threshold intensity for optical limiting for each sample, it can be noticed that the threshold is inversely proportional to the concentration. Also, the data show that as the concentration increases, a reduction in linear transmittance as well as the clamping level is observed. The observed results confirm previous findings that the concentration effect is remarkable [13–15]. Our results show that the absorption coefficient of the sample increased with increase in incident laser intensity. Therefore, we can say that the optical limiting behavior of the Sudan III dye doped into EPDM polymer, corresponding to 10 ns pulses, originated from reverse saturable absorption (RAS). However, several mechanisms
We have presented the measurement results of the optical limiting performance in the Sudan III dye doped into EPDM polymer at 0.2, 0.3, 0.4 and 0.6 mg/g concentrations, using 532 nm, 10 ns pulses from a frequency-doubled Nd–YAG laser. These studies reveal that Sudan III dye can be a promising dopant material and hence can be used in optical limiting applications.
Acknowledgements The authors would like to thank Prof. I. Othman, the General Director, for his encouragement and support.
References [1] Bunning TJ, Natarajan IV, Schmitt MG, Epling BL, Crane RL. Nonlinear optical properties of poylaniline composite materials. Applied Optics 1991;30:4341–9. [2] Tutt LW, Kost A. Optical limiting performance of C60 and C70 solutions. Nature 1992;356:225–6. [3] Chari R, Mishra SR, Rawat HR, Oak SM. Reverse saturable absorption and optical limiting in indanthrone dyes. Applied Physics B 1996;62:293–7. [4] Wang H, Xu J, Yu C. SPIE2321 1994, p.10. [5] Bunning TJ, Natamian LV. Optics Letters 1990;15:700. [6] Sun Ya-Ping, Riggs JE. Organic and inorganic optical limiting materials from fullerenes and nanoparticles. International Reviews in Physical Chemistry 1999;18:43–90. [7] Geethakrishnan T, Palanisamy PK. Z-scan determination of the third-order optical nonlinearity of a triphenylmethane dye using 633 nm He–Ne laser. Optics Communications 2007;270:424–8. [8] Jamshidi-Ghaleh K, Salmani S, Majles Ara MH. Nonlinear responses and optical limiting behavior of fast green FCF dye under a low power CW He–Ne laser irradiation. Optics Communications 2007;271:551–4. [9] George M, Muneer CI, Singh CP, Bindra KS, Oak SM. Z-scan studies and optical limiting of nanosecond laser pulses in neutral red dye. Optics & Laser Technology 2008;40:373–8. [10] Shettigar Seetharam, Umesh G, Chandrasekharan K, Kalluraya Balakrishna. Third-order nonlinear optical properties and two photon absorption in newly synthesized phenyl sydnone doped polymer. Synthetic Metals 2007;157:142–6. [11] Fang Li, Zheng Qiguang, Yang Guang, Dai Nengli, Lu Peixiang. Optical limiting properties of two phthalocyanines using 1064 nm laser in solution. Materials Letters 2008;62:3059–62. [12] Ostuni R, Larciprete MC, Leahu G, Belardini A, Sibilia C, Bertolotti M. Optical limiting behavior of zinc phthalocyanines in polymeric matrix. Journal of Applied Physics 2007;101:033111–6. [13] John Kiran, Nooji Satheesh Rai, Udayakumar D, Chandrasekharan K, Kalluraya B, Philip Reji, et al. Nonlinear optical properties of p-(N,N-dimethylamino) dibenzylideneacetone doped polymer. Materials Research Bulletin 2008;43: 707–13. [14] Riggs JE, Sun Ya-Ping. Optical limiting properties of [60]fullerene and methano[60]fullerene derivative in solution versus in polymer matrix: the role of bimolecular processes and a consistent nonlinear absorption mechanism. Journal of Physical Chemistry A 1999;103:485–95. [15] Harilal SS, Bindhu CV, Nampoori VPN, Vallabhan PG. Optical limiting and thermal lensing studies in C60. Journal of Applied Phyiscs 1999;86(3):1388–92. [16] Hongyao Xu, Jiang Minhua, Song Yinglin, Chunfei Li. Optical limiting of a new substituted polydiacetlene. Materials Letters 1996;27:91–4. [17] Tong R, Wuc H, Lia B, Zhua R, Youa G, Qian Sh, et al. Reverse saturable absorption and optical limiting performance of fullerene-functionalized polycarbonates in femtosecond time scale. Physica B 2005;366:192–9.