Full length article Z-scan measurements of single walled carbon nanotube doped acetylenedicarboxylic acid polymer under CW laser M.D. Zidan n , A.W. Allaf, A. Allahham, A. AL-Zier Department of Physics Atomic Energy Commission, P.O. Box 6091, Damascus, Syria article info Article history: Received 1 October 2015 Received in revised form 9 December 2015 Accepted 4 January 2016 Keywords: ADC polymer Z-scan Single walled carbon nanotubes. abstract Z-scan measurements of single walled carbon nanotube (SWCNT) doped with acetylenedicarboxylic acid (ADC) polymer are performed using a CW diode laser at 635 nm wavelength with 17 mW power. The nonlinear absorption coefficient (β), nonlinear refractive index (n 2 ), the real and imaginary parts of the third-order nonlinear optical susceptibility (Re χ 3 ), (Im χ 3 ) of the investigated samples are calculated. It was found that the β values decrease with increase in on-axis input intensity I 0 . Also, these values are found to be proportional with sample concentrations. The excited-state absorption cross sections were calculated to be at s ex ¼5.08 Â 10 À14 cm 2 for the (SWCNT) and at 15.1 Â 10 À14 cm 2 for the ADC polymer. It was found that the s ex is larger than ground-state absorption cross sections, indicating that the reverse saturable absorption mechanism (RSA) is the dominating mechanism for the observed absorption nonlinearities. & 2016 Elsevier Ltd. All rights reserved. 1. Introduction Since the discovery of the carbon nanotubes (CNTs) in 1991 [1], there have been considerable works on optical limiting effect in order to find out new materials to protect the human eye and optical sensor from high intense laser beams. Their nonlinear optical properties such as: large nonlinearity, broadband spectral response and fast response time are important for realizing the potential of using CNTs material in optical limiting and processing fields [2–5]. Sun et al. [6] and Vivien et al. [7] were reported the first studies of multi-wall carbon nanotubes (MWCNT) and single-wall carbon nanotubes (SWCNT) suspensions, respectively. They compared the optical limiting performance with those of carbon black particles suspensions and fullerenes. Then, z-scan measurements were carried out on CNTs in various solvents (ethylene glycol, water and ethanol), and investigating the solvent effects on the optical lim- iting performance [8,9]. Recently, the nonlinear optical properties of CNTs hybrids composite were investigated using a Z-Scan method. These CNTs composites show a remarkable optical lim- iting performance in comparison with other materials [10,11]. Many reported results show that the combination of the unique properties of CNTs with functional polymers will lead to novel materials with unusual mechanical, electrical, magnetic, optical and chemical properties [12]. Nonlinear optical properties of the CNTs/polymer composites were reported [13,14]. Also, the non- linear refractive index (n 2 ) and nonlinear absorption coefficient (β) of CNTs/polymer were measured at different concentrations. The variations of n 2 and β were noted as concentrations increase [15,16]. This article reports the investigation of nonlinear optical properties of carbon nanotubes (SWCNT) doped acet- ylenedicarboxylic acid (ADC) polymer using the z-scan technique by a CW diode laser at 635 nm wavelength and a power of 17 mW. To our knowledge, there is no report published before on in- vestigation of the nonlinear optical properties of (SWCNT) doped ADC Polymer. 2. Experimental techniques The carbon nanotubes were purchased from Sigma-Aldrich and used as received without any purification. The carbon nanotubes are dissolved in 1, 2-dichlorobenzene solvent. The concentrations of ADC polymer and (SWCNT) solutions were 1 Â 10 À3 M and 5 Â 10 À3 M, respectively. ADC polymer has been prepared recently and identified using different techniques such as: 1 H, 13 C NMR, FTIR, and measuring the number of average molecular weight including the thermal ana- lysis [17]. The Z-scan experimental set-up was analogous to that de- scribed in Ref. [18]. The measurements were carried out with a linearly polarized TEM 00 Gaussian beam of a CW diode laser at 17 mW (λ ¼ 635 nm). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/optlastec Optics & Laser Technology http://dx.doi.org/10.1016/j.optlastec.2016.01.011 0030-3992/& 2016 Elsevier Ltd. All rights reserved. n Corresponding author. E-mail address: pscientific8@aec.org.sy (M.D. Zidan). Optics & Laser Technology 80 (2016) 72–76