Nonlinear response of nano-particles birnessite-type Manganese oxide (γ-MnO2)

Nano-particle materials with large optical nonlinearities are in great need for the development of nonlinear optical technology and are being studied intensively in recent years. In this work, birnessite-type Manganese oxide (γ-MnO2) nano-particles have been synthesized by Gelation routes method. These nano-particles were characterized by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) and Z-scan technique. The size of these nano-particles obtained by XRD pattern was 21.7nm, furthermore XRD pattern revealed the tetragonal structure of (γ-MnO2) nano-particles. The average particle size obtained from SEM analysis was about 50nm. At first the linear absorption for these nano-particles was calculated by optical limiting (OL) setup to be about α=3.9cm−1w. We measured the nonlinear optical properties of (γ-MnO2) nano-particles using close and open-aperture Z-scan by continuous-wave (CW) He–Ne laser with a wavelength of 632.8nm at different incident powers. The nonlinear refractive indices of (γ-MnO2) nano-particles, n2, were measured in order of 10−7cm2/w with negative sign and the nonlinear absorption coefficient of(γ-MnO2) nano-particles, β, was obtained in order of 10−2cm/w. These results showed that birnessite-type Manganese oxide (γ-MnO2) nano-particles have potential applications in nonlinear optics.