Near-IR nonlinear optical filter for optical communication window Viatcheslav V. Vanyukov,1,* Gennady M. Mikheev,2 Tatyana N. Mogileva,2 Alexey P. Puzyr,3 Vladimir S. Bondar,3 and Yuri P. Svirko1 1
Institute of Photonics, University of Eastern Finland, Joensuu, Finland
2
Institute of Mechanics, Russian Academy of Sciences, Izhevsk, Russia
3
Institute of Biophysics, Russian Academy of Sciences, Krasnoyarsk, Russia *Corresponding author: [email protected]
Received 20 November 2014; revised 3 March 2015; accepted 7 March 2015; posted 9 March 2015 (Doc. ID 228232); published 8 April 2015
We report on a high performance nonlinear optical filter for the telecommunication window that employs detonation nanodiamonds (NDs). The nanosecond Z-scan experiments revealed that the heavy water ND suspensions enable strong optical limiting in the wavelength range of 1400–1675 nm. We observed an enhancement of the optical limiting performance in the blue part of the communication window. In particular, at the wavelength of 1400 nm the transmittance of the 2 mm thick sample with 4.5 wt. % ND concentration is suppressed by 45% for the input fluence of 3.8 J∕cm2 . The proposed nonlinear optical filter employs the phenomena of the nonlinear absorption and the nonlinear light scattering in ND suspensions. © 2015 Optical Society of America OCIS codes: (160.4236) Nanomaterials; (190.4400) Nonlinear optics, materials. http://dx.doi.org/10.1364/AO.54.003290
1. Introduction
Nonlinear filters and optical limiters are devices capable to protect optical sensors by attenuating potentially damaging powerful laser radiation [1]. Since the response time, limiting power threshold, and working spectrum range are the key parameters of an optical limiter [2,3], nanocarbon materials are widely recognized as very promising for the optical limiting (OL) applications [4]. Fast optical nonlinearity and a low limiting threshold [5] allow one to employ carbon nanotubes, carbon black, graphene, carbon dots, and nanodiamonds (NDs) for the OL in the visual and the near-infrared (NIR) spectrum ranges. The latter makes these materials of high importance for suppression of the intensity fluctuations in optical telecommunications and data-processing systems working in the wavelength range of 1559-128X/15/113290-04$15.00/0 © 2015 Optical Society of America 3290
APPLIED OPTICS / Vol. 54, No. 11 / 10 April 2015
1400–1600 nm [6]. In nanocarbon materials, the OL may originate from the various processes, including nonlinear refraction, nonlinear absorption, and nonlinear scattering. It has been shown that in nanocarbon suspensions, a nonlinear scattering [7,8] caused by the formation of bubbles, sublimation of carbons and microplasma dominate OL in the visual spectrum range making possible in particular to control the temporal profile of the laser pulse [9]. However, in the NIR range (1100–2500 nm), the information on the nonlinear filtering with nanocarbon materials is rather limited [10,11]. This is partially because conventional solvents, including ethanol, toluene, dimethylformamide, distilled water, etc., strongly absorb radiation in the NIR range [12], i.e., they cannot be employed for preparing of nanocarbon suspensions. In order to evaluate the OL performance of the nanocarbon materials in the optical communication window we perform measurements in heavy water (D2 O) suspensions of detonation NDs. In this paper
we demonstrate that the strong optical nonlinearity [5] along with a high colloidal and ray stability [13,14] makes it possible to employ these suspensions for nonlinear filtering and stabilization of the high-intensity optical pulses in the wavelength range of 1400–1675 nm. 2. Methods and Materials
In experiments, we studied the ND clusters manufactured using commercially available RDDM (Real Dzerzhinsk Ltd., Russia) NDs [15]. In order to remove surface impurities and to improve the colloidal stability of the suspension, the ND clusters were treated in NaCl solution at atmospheric pressure and room temperature. This significantly advances the stability of the ND suspension with respect to sedimentation. The x-ray diffraction pattern and the high-resolution transmission electron microscopy measurements showed that the treatment did not affect the ND crystallinity (see [14,15] for details). The treated ND clusters with a modified surface were suspended in the D2 O by ultrasonication. The obtained ND suspensions possess a high colloidal stability maintaining their optical properties for more than 1 year. The main distinctive feature of these suspensions is that the ND clusters did not change their properties upon drying, i.e., they can be reused to make stable suspension again, if necessary [15]. By using the Malvern Zetasizer Nano ZS particle size analyzer, we revealed in particular that an average ND cluster size remains the same after drying. This ensures that changing the ND concentration does not lead to significant changes in the sizes of the ND clusters. For the OL measurements, we prepared 3 and 4.5 wt. % ND suspensions. We studied the OL in ND suspensions with an average cluster size of 110 nm. The thickness of all samples was 2 mm. D2 O was employed as a host liquid because of its low (in comparison with H2 O, see inset to Fig. 1) absorption in the wavelength region of 1100–1600 nm [16]. The data shown in Fig. 1 are consistent with previous reported [17], specifically one
Fig. 1. NIR optical density of 2 mm thick samples with ND concentrations of 3 (1) and 4.5 wt. % (2) as functions of the wavelength. Optical density is measured relative to heavy water. The inset shows the optical density spectra of 2 mm thick samples of water and heavy water relative to air.
Fig. 2. Sketch of the open-aperture Z-scan experimental setup.
can observe that in the studied wavelength range, the longer the wavelength, the higher the optical density of the ND suspensions. 3. Experimental Technique
In order to evaluate the OL performance of the fabricated suspensions in the NIR spectrum range, we employed a conventional open-aperture Z-scan setup that enables simultaneous measurement of the energy of the transmitted and scattered at 90 deg pulses as a function of sample position z [7]. z 0 corresponds to the position of the focal point at the center of the sample (see Fig. 2). In the nonlinear optical measurements we employed the optical parametrical amplifier (OPA, Laser Vision, USA) pumped by the first and the second harmonics of the YAG:Nd3 laser with 7 ns pulses at a repetition rate of 2 Hz. The output radiation in the wavelength range of 1350–5000 nm was spatially filtered in order to obtain a single-mode beam. The diameter of the beam waist at 1∕e2 intensity level at a wavelength of 1500 nm was 2w0 60 μm. The nonlinear optical response of the ND samples was measured at seven different wavelengths of 1400, 1450, 1500, 1550, 1600, 1650, and 1675 nm at the pulse energy of Ein 0.2 mJ. At wavelength of 1500 nm, the incident fluence z 0 was 3.8 J∕cm2. The incident fluence at other wavelengths was calculated with taking into account the dependence of the beam on the wavelength. 4. Results and Discussion
Figure 3 shows the normalized transmittance at wavelengths of 1400, 1450, 1500, 1600, and 1675 nm as a function of the sample position. For all the wavelengths, one can clearly observe the OL of the incident laser pulse, i.e., the reduction of the sample transmittance when the light fluence increases. It is worth noting that for the both studied samples, the maximum attenuation was achieved at the shortest wavelength. In particular, for the suspension with 4.5 wt. % ND concentration, the suppression of the transmittance was as high as 45% at a wavelength of 1400 nm. The extremum in the normalized transmission curve at the ND concentration of 4.5 wt. % [Fig. 3(b)] is broader than that at the ND concentration of 3 wt. % [Fig. 3(a)]. This is due to the higher OL efficiency [18] and the lower OL threshold [14] when the ND concentration increases. In the Z-scan experiment, this means that the higher the concentration, the bigger the displacement of the sample from the focus (i.e., the bigger z) when the OL is observed. 10 April 2015 / Vol. 54, No. 11 / APPLIED OPTICS
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C=4.5%
C=4.5%
1
0.8 1675 nm 1600 nm 1500 nm 1450 nm 1400 nm
0.6
0.4 -10
-5
0
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5
10
1675 nm 1600 nm 1500 nm 1450 nm 1400 nm
-5
0
5
Normalized transmittance
Normalized transmittance
C=3%
1
1
0.8
0.8
0.6
0.6
λ =1550 nm Ein=0.33 mJ
10
z, mm
Fig. 3. Normalized transmittance of the heavy water ND suspensions with (a) 3 and (b) 4.5 wt. % concentrations as a function of z. z 0 corresponds to the position of the focal point at the center of the sample. The measurements were performed at the incident pulse energy of 0.2 mJ and the pulse duration of 7 ns.
The OL efficiency η can be quantitatively characterized by the ratio of the transmittance T 0 measured at jzj > 5 mm (low fluence, see Fig. 3) to the transmittance T nl measured at z 0 (when the fluence is maximum), i.e., η T 0 ∕T nl [19]. The dependence of η on the OPA wavelength in Fig. 4 clearly shows the decrease of the OL efficiency with the increase of the wavelength. This effect may originate from the lower absorption coefficient of the light as well as from the decreasing of the light-scattered cross section [18] at longer wavelengths. The important role of the nonlinear scattering in the observed effect was confirmed by the measurements of the energy of the light pulses scattered at 90 deg with respect to the incident beam (see Fig. 2) [20]. The simultaneously recorded normalized transmittance and the scattered at 90 deg pulse energy for the sample with 4.5 wt. % ND concentration are given in Fig. 5. As one can see from the figure, the minimum of the sample transmittance corresponds to the maximum scattered energy, confirming a direct link between the power limiting and an increase of the scattering cross-section. At the same time, coincidence slight asymmetry of the normalized
0.4 -10
Normalized energy of scattered pulse
1.2
0.4
-5
0
5
10
z, mm Fig. 5. Normalized transmittance (solid blue circle) and the normalized energy of the scattered pulse (open diamond) as a function of sample position z relative to the focal plane. The measurements are performed at the wavelength of 1550 nm at the pulse energy of 0.33 mJ.
transmission curves presented in Fig. 5 can be attributed to the nonlinear absorption contribution. It is worth noting that in our recent publication [14], we have demonstrated that in the closed-aperture Z-scan technique, the transmittance of ND suspension is an even function of z at the pulse energy of 30 μJ. This indicates that nonlinear refraction contribution to the OL in this suspension is negligible. The nonlinear scattering in the suspension with 4.5 wt. % concentration of ND clusters is stronger than that in the suspension with 3 wt. % concentration. Correspondingly, the dependence of the transmittance on the sample position in Fig. 3(b) is more pronounced than that in Fig. 3(a). This experimental finding is consistent with results obtained at the fundamental wavelength of a YAG:Nd3 laser and originates from the increasing of the number of the scattering centers in the focal volume when the ND concentration increases [20,21]. 5. Conclusion
In conclusion, we demonstrate that the heavy water suspensions of the detonation ND possess a high ray and colloidal stability and enable efficient optical limiting in the wavelength range of 1400–1675 nm. In this nanocarbon material, the efficiency of the nonlinear filtering, which originates from the pronounced nonlinear absorption and the nonlinear scattering rather than from the nonlinear refraction of the incident light beam, decreases with increasing the wavelength. The observed nonlinear filtering makes D2 O ND suspension a prospective material for photonic and optical data processing devices operating in the optical communication window. Fig. 4. Wavelength dependence of the OL efficiency η for ND clusters dispersed in D2 O with mass concentrations of 3 (1) and 4.5 wt. % (2). The sample thickness is 2 mm. Vertical lines show the standard deviation of the experimental data from the mean values. 3292
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This work was supported by the Academy of Finland (grants no. 278252 and no. 288547), the Emil Aaltosen Säätio foundation, Russian Foundation for Basic Research (project no. 13-02-96016 r_ural_a), the Erasmus staff exchange support
(Dno 275/04.04.02.01), and FP7 Marie Curie project FANCEE. References 1. G. Ritt, S. Dengler, and B. Eberle, “Protection of optical systems against laser radiation,” Proc. SPIE 7481, 74810U (2009). 2. C. Zhang, Y. Song, F. Kuhn, Y. Wang, X. Xin, and W. Herrman, “Ultrafast response and superior optical limiting effects of planar ‘open’ heterothiometallic clusters,” Adv. Mater. 14, 818–822 (2002). 3. R. Gvishi, P. Zhao, H. Hu, G. Strum, A. Tal, S. Grinvald, G. Bar, L. Bekere, V. Lokshin, V. Khodorkovsky, M. Sigalov, D. Hagan, and E. V. Stryland, “Nonlinear solid-state filter based on photochromism induced by 2-photon absorption in a dye-doped sol-gel,” Proc. SPIE 9181, 91810J (2014). 4. J. Wang, Y. Chen, R. Li, H. Dong, L. Zhang, M. Lotya, J. Coleman, and W. Blau, “Nonlinear optical properties of graphene and carbon nanotube composites,” in Carbon Nanotubes—Synthesis, Characterization, Application, S. Yellampalli, ed. (InTech, 2011), pp. 397–424. 5. I. Papagiannouli, A. B. Bourlinos, A. Bakandritsos, and S. Couris, “Nonlinear optical properties of colloidal carbon nanoparticles: nanodiamonds and carbon dots,” RSC Adv. 4, 40152–40160 (2014). 6. P.-A. Bouit, G. Wetzel, G. Berginc, B. Loiseaux, L. Toupet, P. Feneyrou, Y. Bretonniere, K. Kamada, O. Maury, and C. Andraud, “Near IR nonlinear absorbing chromophores with optical limiting properties at telecommunication wavelengths,” Chem. Mater. 19, 5325–5335 (2007). 7. G. M. Mikheev, A. P. Puzyr, V. V. Vanyukov, K. V. Purtov, T. N. Mogileva, and V. S. Bondar, “Nonlinear scattering of light in nanodiamond hydrosol,” Tech. Phys. Lett. 36, 358–361 (2010). 8. L. Vivien, D. Riehl, F. Hache, and E. Anglaret, “Nonlinear scattering origin in carbon nanotube suspensions,” J. Nonlinear Opt. Phys. Mater. 9, 297–307 (2000). 9. V. V. Vanyukov, T. N. Mogileva, G. M. Mikheev, A. V. Okotrub, and D. L. Bulatov, “Application of nonlinear light scattering in nanocarbon suspensions for adjustment of laser pulse duration,” J. Nanoelectron. Optoelectron. 7, 102–106 (2012).
10. N. V. Kamanina, M. O. Iskandarov, and A. A. Nikitichev, “Middle infrared optical investigations of fullerene–2-(nprolinol)-5-nitropyridine,” Opt. Commun. 225, 337–340 (2003). 11. N. Liaros, E. Koudoumas, and S. Couris, “Broadband near infrared optical power limiting of few layered graphene oxides,” Appl. Phys. Lett. 104, 191112 (2014). 12. L. A. Kazicina and N. B. Kupletskaya, Application of UV-, IRand NMR Spectroscopy in Organic Chemistry (Chemistry Publ., 1971). 13. N. Gibson, O. Shenderova, T. Luo, S. Moseenkov, V. Bondar, A. Puzir, K. Purtov, Z. Fitzgerald, and D. Brenner, “Colloidal stability of modified nanodiamond particles,” Diamond Relat. Mater. 18, 620–626 (2009). 14. V. V. Vanyukov, T. N. Mogileva, G. M. Mikheev, A. P. Puzyr, V. S. Bondar, and Y. P. Svirko, “Size effect on the optical limiting in suspensions of detonation nanodiamond clusters,” Appl. Opt. 52, 4123–4130 (2013). 15. V. S. Bondar and A. P. Puzyr, “Nanodiamonds for biological investigations,” Phys. Solid State 46, 716–719 (2004). 16. C. L. Braun and S. N. Smirnov, “Why is water blue?” J. Chem. Educ. 70, 612–614 (1993). 17. A. E. Aleksenskii, A. U. Vul, S. V. Konyakhin, K. V. Reich, L. V. Sharonova, and E. D. Eidelman, “Optical properties of detonation nanodiamond hydrosol,” Phys. Solid State 54, 578–585 (2012). 18. C. F. Bohren and D. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, 1983). 19. S. H. Chi, J. M. Hales, M. Cozzuol, C. Ochoa, M. Fitzpatrick, and J. W. Perry, “Conjugated polymer-fullerene blend with strong optical limiting in the near-infrared,” Opt. Express 17, 22062–22072 (2009). 20. V. V. Vanyukov, G. M. Mikheev, T. N. Mogileva, A. P. Puzyr, V. S. Bondar, and Y. P. Svirko, “Concentration dependence of the optical limiting and nonlinear light scattering in aqueous suspensions of detonation nanodiamond clusters,” Opt. Mater. 37, 218–222 (2014). 21. S. Josset, O. Muller, L. Schmidlin, V. Pichot, and D. Splitzer, “Nonlinear optical properties of detonation nanodiamond in the near infrared: effects of concentration and size distribution,” Diamond Relat. Mater. 32, 66–71 (2013).
10 April 2015 / Vol. 54, No. 11 / APPLIED OPTICS
3293
Institute of Photonics, University of Eastern Finland, Joensuu, Finland
2
Institute of Mechanics, Russian Academy of Sciences, Izhevsk, Russia
3
Institute of Biophysics, Russian Academy of Sciences, Krasnoyarsk, Russia *Corresponding author: [email protected]
Received 20 November 2014; revised 3 March 2015; accepted 7 March 2015; posted 9 March 2015 (Doc. ID 228232); published 8 April 2015
We report on a high performance nonlinear optical filter for the telecommunication window that employs detonation nanodiamonds (NDs). The nanosecond Z-scan experiments revealed that the heavy water ND suspensions enable strong optical limiting in the wavelength range of 1400–1675 nm. We observed an enhancement of the optical limiting performance in the blue part of the communication window. In particular, at the wavelength of 1400 nm the transmittance of the 2 mm thick sample with 4.5 wt. % ND concentration is suppressed by 45% for the input fluence of 3.8 J∕cm2 . The proposed nonlinear optical filter employs the phenomena of the nonlinear absorption and the nonlinear light scattering in ND suspensions. © 2015 Optical Society of America OCIS codes: (160.4236) Nanomaterials; (190.4400) Nonlinear optics, materials. http://dx.doi.org/10.1364/AO.54.003290
1. Introduction
Nonlinear filters and optical limiters are devices capable to protect optical sensors by attenuating potentially damaging powerful laser radiation [1]. Since the response time, limiting power threshold, and working spectrum range are the key parameters of an optical limiter [2,3], nanocarbon materials are widely recognized as very promising for the optical limiting (OL) applications [4]. Fast optical nonlinearity and a low limiting threshold [5] allow one to employ carbon nanotubes, carbon black, graphene, carbon dots, and nanodiamonds (NDs) for the OL in the visual and the near-infrared (NIR) spectrum ranges. The latter makes these materials of high importance for suppression of the intensity fluctuations in optical telecommunications and data-processing systems working in the wavelength range of 1559-128X/15/113290-04$15.00/0 © 2015 Optical Society of America 3290
APPLIED OPTICS / Vol. 54, No. 11 / 10 April 2015
1400–1600 nm [6]. In nanocarbon materials, the OL may originate from the various processes, including nonlinear refraction, nonlinear absorption, and nonlinear scattering. It has been shown that in nanocarbon suspensions, a nonlinear scattering [7,8] caused by the formation of bubbles, sublimation of carbons and microplasma dominate OL in the visual spectrum range making possible in particular to control the temporal profile of the laser pulse [9]. However, in the NIR range (1100–2500 nm), the information on the nonlinear filtering with nanocarbon materials is rather limited [10,11]. This is partially because conventional solvents, including ethanol, toluene, dimethylformamide, distilled water, etc., strongly absorb radiation in the NIR range [12], i.e., they cannot be employed for preparing of nanocarbon suspensions. In order to evaluate the OL performance of the nanocarbon materials in the optical communication window we perform measurements in heavy water (D2 O) suspensions of detonation NDs. In this paper
we demonstrate that the strong optical nonlinearity [5] along with a high colloidal and ray stability [13,14] makes it possible to employ these suspensions for nonlinear filtering and stabilization of the high-intensity optical pulses in the wavelength range of 1400–1675 nm. 2. Methods and Materials
In experiments, we studied the ND clusters manufactured using commercially available RDDM (Real Dzerzhinsk Ltd., Russia) NDs [15]. In order to remove surface impurities and to improve the colloidal stability of the suspension, the ND clusters were treated in NaCl solution at atmospheric pressure and room temperature. This significantly advances the stability of the ND suspension with respect to sedimentation. The x-ray diffraction pattern and the high-resolution transmission electron microscopy measurements showed that the treatment did not affect the ND crystallinity (see [14,15] for details). The treated ND clusters with a modified surface were suspended in the D2 O by ultrasonication. The obtained ND suspensions possess a high colloidal stability maintaining their optical properties for more than 1 year. The main distinctive feature of these suspensions is that the ND clusters did not change their properties upon drying, i.e., they can be reused to make stable suspension again, if necessary [15]. By using the Malvern Zetasizer Nano ZS particle size analyzer, we revealed in particular that an average ND cluster size remains the same after drying. This ensures that changing the ND concentration does not lead to significant changes in the sizes of the ND clusters. For the OL measurements, we prepared 3 and 4.5 wt. % ND suspensions. We studied the OL in ND suspensions with an average cluster size of 110 nm. The thickness of all samples was 2 mm. D2 O was employed as a host liquid because of its low (in comparison with H2 O, see inset to Fig. 1) absorption in the wavelength region of 1100–1600 nm [16]. The data shown in Fig. 1 are consistent with previous reported [17], specifically one
Fig. 1. NIR optical density of 2 mm thick samples with ND concentrations of 3 (1) and 4.5 wt. % (2) as functions of the wavelength. Optical density is measured relative to heavy water. The inset shows the optical density spectra of 2 mm thick samples of water and heavy water relative to air.
Fig. 2. Sketch of the open-aperture Z-scan experimental setup.
can observe that in the studied wavelength range, the longer the wavelength, the higher the optical density of the ND suspensions. 3. Experimental Technique
In order to evaluate the OL performance of the fabricated suspensions in the NIR spectrum range, we employed a conventional open-aperture Z-scan setup that enables simultaneous measurement of the energy of the transmitted and scattered at 90 deg pulses as a function of sample position z [7]. z 0 corresponds to the position of the focal point at the center of the sample (see Fig. 2). In the nonlinear optical measurements we employed the optical parametrical amplifier (OPA, Laser Vision, USA) pumped by the first and the second harmonics of the YAG:Nd3 laser with 7 ns pulses at a repetition rate of 2 Hz. The output radiation in the wavelength range of 1350–5000 nm was spatially filtered in order to obtain a single-mode beam. The diameter of the beam waist at 1∕e2 intensity level at a wavelength of 1500 nm was 2w0 60 μm. The nonlinear optical response of the ND samples was measured at seven different wavelengths of 1400, 1450, 1500, 1550, 1600, 1650, and 1675 nm at the pulse energy of Ein 0.2 mJ. At wavelength of 1500 nm, the incident fluence z 0 was 3.8 J∕cm2. The incident fluence at other wavelengths was calculated with taking into account the dependence of the beam on the wavelength. 4. Results and Discussion
Figure 3 shows the normalized transmittance at wavelengths of 1400, 1450, 1500, 1600, and 1675 nm as a function of the sample position. For all the wavelengths, one can clearly observe the OL of the incident laser pulse, i.e., the reduction of the sample transmittance when the light fluence increases. It is worth noting that for the both studied samples, the maximum attenuation was achieved at the shortest wavelength. In particular, for the suspension with 4.5 wt. % ND concentration, the suppression of the transmittance was as high as 45% at a wavelength of 1400 nm. The extremum in the normalized transmission curve at the ND concentration of 4.5 wt. % [Fig. 3(b)] is broader than that at the ND concentration of 3 wt. % [Fig. 3(a)]. This is due to the higher OL efficiency [18] and the lower OL threshold [14] when the ND concentration increases. In the Z-scan experiment, this means that the higher the concentration, the bigger the displacement of the sample from the focus (i.e., the bigger z) when the OL is observed. 10 April 2015 / Vol. 54, No. 11 / APPLIED OPTICS
3291
C=4.5%
C=4.5%
1
0.8 1675 nm 1600 nm 1500 nm 1450 nm 1400 nm
0.6
0.4 -10
-5
0
z, mm
5
10
1675 nm 1600 nm 1500 nm 1450 nm 1400 nm
-5
0
5
Normalized transmittance
Normalized transmittance
C=3%
1
1
0.8
0.8
0.6
0.6
λ =1550 nm Ein=0.33 mJ
10
z, mm
Fig. 3. Normalized transmittance of the heavy water ND suspensions with (a) 3 and (b) 4.5 wt. % concentrations as a function of z. z 0 corresponds to the position of the focal point at the center of the sample. The measurements were performed at the incident pulse energy of 0.2 mJ and the pulse duration of 7 ns.
The OL efficiency η can be quantitatively characterized by the ratio of the transmittance T 0 measured at jzj > 5 mm (low fluence, see Fig. 3) to the transmittance T nl measured at z 0 (when the fluence is maximum), i.e., η T 0 ∕T nl [19]. The dependence of η on the OPA wavelength in Fig. 4 clearly shows the decrease of the OL efficiency with the increase of the wavelength. This effect may originate from the lower absorption coefficient of the light as well as from the decreasing of the light-scattered cross section [18] at longer wavelengths. The important role of the nonlinear scattering in the observed effect was confirmed by the measurements of the energy of the light pulses scattered at 90 deg with respect to the incident beam (see Fig. 2) [20]. The simultaneously recorded normalized transmittance and the scattered at 90 deg pulse energy for the sample with 4.5 wt. % ND concentration are given in Fig. 5. As one can see from the figure, the minimum of the sample transmittance corresponds to the maximum scattered energy, confirming a direct link between the power limiting and an increase of the scattering cross-section. At the same time, coincidence slight asymmetry of the normalized
0.4 -10
Normalized energy of scattered pulse
1.2
0.4
-5
0
5
10
z, mm Fig. 5. Normalized transmittance (solid blue circle) and the normalized energy of the scattered pulse (open diamond) as a function of sample position z relative to the focal plane. The measurements are performed at the wavelength of 1550 nm at the pulse energy of 0.33 mJ.
transmission curves presented in Fig. 5 can be attributed to the nonlinear absorption contribution. It is worth noting that in our recent publication [14], we have demonstrated that in the closed-aperture Z-scan technique, the transmittance of ND suspension is an even function of z at the pulse energy of 30 μJ. This indicates that nonlinear refraction contribution to the OL in this suspension is negligible. The nonlinear scattering in the suspension with 4.5 wt. % concentration of ND clusters is stronger than that in the suspension with 3 wt. % concentration. Correspondingly, the dependence of the transmittance on the sample position in Fig. 3(b) is more pronounced than that in Fig. 3(a). This experimental finding is consistent with results obtained at the fundamental wavelength of a YAG:Nd3 laser and originates from the increasing of the number of the scattering centers in the focal volume when the ND concentration increases [20,21]. 5. Conclusion
In conclusion, we demonstrate that the heavy water suspensions of the detonation ND possess a high ray and colloidal stability and enable efficient optical limiting in the wavelength range of 1400–1675 nm. In this nanocarbon material, the efficiency of the nonlinear filtering, which originates from the pronounced nonlinear absorption and the nonlinear scattering rather than from the nonlinear refraction of the incident light beam, decreases with increasing the wavelength. The observed nonlinear filtering makes D2 O ND suspension a prospective material for photonic and optical data processing devices operating in the optical communication window. Fig. 4. Wavelength dependence of the OL efficiency η for ND clusters dispersed in D2 O with mass concentrations of 3 (1) and 4.5 wt. % (2). The sample thickness is 2 mm. Vertical lines show the standard deviation of the experimental data from the mean values. 3292
APPLIED OPTICS / Vol. 54, No. 11 / 10 April 2015
This work was supported by the Academy of Finland (grants no. 278252 and no. 288547), the Emil Aaltosen Säätio foundation, Russian Foundation for Basic Research (project no. 13-02-96016 r_ural_a), the Erasmus staff exchange support
(Dno 275/04.04.02.01), and FP7 Marie Curie project FANCEE. References 1. G. Ritt, S. Dengler, and B. Eberle, “Protection of optical systems against laser radiation,” Proc. SPIE 7481, 74810U (2009). 2. C. Zhang, Y. Song, F. Kuhn, Y. Wang, X. Xin, and W. Herrman, “Ultrafast response and superior optical limiting effects of planar ‘open’ heterothiometallic clusters,” Adv. Mater. 14, 818–822 (2002). 3. R. Gvishi, P. Zhao, H. Hu, G. Strum, A. Tal, S. Grinvald, G. Bar, L. Bekere, V. Lokshin, V. Khodorkovsky, M. Sigalov, D. Hagan, and E. V. Stryland, “Nonlinear solid-state filter based on photochromism induced by 2-photon absorption in a dye-doped sol-gel,” Proc. SPIE 9181, 91810J (2014). 4. J. Wang, Y. Chen, R. Li, H. Dong, L. Zhang, M. Lotya, J. Coleman, and W. Blau, “Nonlinear optical properties of graphene and carbon nanotube composites,” in Carbon Nanotubes—Synthesis, Characterization, Application, S. Yellampalli, ed. (InTech, 2011), pp. 397–424. 5. I. Papagiannouli, A. B. Bourlinos, A. Bakandritsos, and S. Couris, “Nonlinear optical properties of colloidal carbon nanoparticles: nanodiamonds and carbon dots,” RSC Adv. 4, 40152–40160 (2014). 6. P.-A. Bouit, G. Wetzel, G. Berginc, B. Loiseaux, L. Toupet, P. Feneyrou, Y. Bretonniere, K. Kamada, O. Maury, and C. Andraud, “Near IR nonlinear absorbing chromophores with optical limiting properties at telecommunication wavelengths,” Chem. Mater. 19, 5325–5335 (2007). 7. G. M. Mikheev, A. P. Puzyr, V. V. Vanyukov, K. V. Purtov, T. N. Mogileva, and V. S. Bondar, “Nonlinear scattering of light in nanodiamond hydrosol,” Tech. Phys. Lett. 36, 358–361 (2010). 8. L. Vivien, D. Riehl, F. Hache, and E. Anglaret, “Nonlinear scattering origin in carbon nanotube suspensions,” J. Nonlinear Opt. Phys. Mater. 9, 297–307 (2000). 9. V. V. Vanyukov, T. N. Mogileva, G. M. Mikheev, A. V. Okotrub, and D. L. Bulatov, “Application of nonlinear light scattering in nanocarbon suspensions for adjustment of laser pulse duration,” J. Nanoelectron. Optoelectron. 7, 102–106 (2012).
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