Investigation of optical nonlinearity and diffraction ring patterns of carbon nanotubes

The third order nonlinear optical properties of multi-wall carbon nanotubes (MWNT), single-wall carbon nanotubes (SWNT) dissolved in 1,2-dichlorobenzene and SWNT doped poly(ethylacetylenecarboxylate) polymer have been studied using Z-scan technique. Experiments are performed using a CW diode laser at 635 nm wavelength with 26 mW power. It has been found that the values of nonlinear absorption coefficient beta, nonlinear refractive index n(2), Re chi(3), and Im chi(3) in SWNT are larger than in MWNT. It was noticed that the closed-aperture Z-scan is most effective when the linear transmittance of the aperture S is small. Laser-induced diffraction ring patterns were observed only for SWNT. Based on the number of diffraction rings, variation of refractive index An and the relative phase shift Delta phi((r)) have been estimated at different input laser power: 5, 10, 15 and 25 mW. (C) 2013 Elsevier Ltd. All rights reserved.