Litty, Irimpan; Deepthy, A; Bindu, Krishnan; Nampoori, V P N; Radhakrishnan, P(Springer, 2008)
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Abstract:
In the present work, we have investigated the nonlinear
optical properties of self-assembled films formed from
ZnO colloidal spheres by z-scan technique. The sign of the nonlinear
component of refractive index of the material remains
the same; however, a switching from reverse saturable absorption
to saturable absorption has been observed as the material
changes from colloid to self-assembled film. These different
nonlinear characteristics can be mainly attributed to ZnO defect
states and electronic effects when the colloidal solution is
transformed into self-assembled monolayers. We investigated
the intensity, wavelength and size dependence of saturable and
reverse saturable absorption of ZnO self-assembled films and
colloids. Values of the imaginary part of third-order susceptibility
are calculated for particles of size in the range 20–300 nm
at different intensity levels ranging from 40 to 325MW/cm2
within the wavelength range of 450–650 nm.