Effect of self assembly on the nonlinear optical characteristics of ZnO thin films

Abstract

In the present work, we report the third order nonlinear optical properties of ZnO thin films deposited using self assembly, sol gel process as well as pulsed laser ablation by z scan technique. ZnO thin films clearly exhibit a negative nonlinear index of refraction at 532 nm and the observed nonlinear refraction is attributed to two photon absorption followed by free carrier absorption. Although the absolute nonlinear values for these films are comparable, there is a change in the sign of the absorptive nonlinearity of the films. The films developed by dip coating and pulsed laser ablation exhibit reverse saturable absorption whereas the self assembled film exhibits saturable absorption. These different nonlinear characteristics in the self assembled films can be mainly attributed to the saturation of linear absorption of the ZnO defect states.

The wide band gap of highly oriented nanocrystalline Al doped ZnO thin films from sol–gel dip coating

“…It had been noticed that the optical band gap of thin films is enhanced from 3.70 eV (undoped ZnO thin film) to 3.75 and 3.87 eV in the case of 5 mol% and 8 mol% Al doped ZnO thin films, respectively. These values were wider than the band gap in [23]. The increase in the band gap (or blue shift) can be explained by the Burstein-Moss band gap widening and band gap narrowing due to the electron-electron and electron-impurity scattering [24].…”

Nonlinear optical characteristics of nanocomposites of ZnO–TiO2–SiO2

“…The samples having xZnO-TiO 2 -SiO 2 composition of (x=) 1%, 2%, 3% 5% are named as 1ZnO-TiO 2 -SiO 2 , 2ZnO-TiO 2 -SiO 2 , 3ZnO-TiO 2 -SiO 2 and 5ZnO-TiO 2 -SiO 2 respectively.The ZnOTiO 2 -SiO 2 nanocomposites are characterized by optical absorption measurements recorded using a spectrophotometer (JascoV-570 UV/VIS/IR) In the present investigation, we have employed the single beam z scan technique with nanosecond laser pulses to measure nonlinear optical absorptive and refractive properties of ZnO-TiO 2 -SiO 2 nanocomposites. z Scan technique developed by Sheik Bahae and his co-workers is a single beam method for measuring the sign and magnitude of nonlinear refractive index, n 2 , and has a sensitivity comparable to interferometric methods [9,10]. A Q-switched Nd:YAG laser (Spectra Physics LAB-1760, 532 nm, 7 ns, 10 Hz) is used as the light source.…”

Magnetic and nonlinear optical properties of BaTiO3 nanoparticles

“…49 Since the higher value for N e is obtained from Z-scan measurements for all particles, in addition to some of the particles displaying narrowed band, with negative refractive index (n 2 ) and bleached optical absorption, the presence of higher concentrations of charge carriers in these particles can be concluded. [50][51][52][53] The higher band gap for these particles is expected due to the mixing up of O 2p states in the valence band and Ti 3d states in the conduction band. This mixing increases the effective mass of electrons in the conduction band and hence there is now effective band narrowing like the other two particle sizes.…”