Investigation of optical nonlinearity and diffraction ring patterns of carbon nanotubes

Abstract

Abstract 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 β, nonlinear refractive index n2, Re χ3, and Im χ3 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 Δn and the relative phase shift ∆ϕ(r) have been estimated at different input laser power: 5, 10, 15 and 25 mW.