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13 papers
Nonlinear optical phenomena
Study of nonlinear optical properties of TiO2 – polystyrene nanocomposite films
M. Zeinalia,
B. Jaleha,
M. R. Rashidian Vazirib,
A. Omidvara a Department of Physics, Bu-Ali Sina University, Iran
b Photonics and Quantum Technologies Research School, Nuclear Science & Technology Research Institute, Iran
Abstract:
We consider an ex-situ prepared TiO
2 – polystyrene (TiO
2 – PS) nanocomposite, with different concentration of TiO
2 nanoparticles (NPs), deposited by the spin-coating method on quartz substrates. Nonlinear optical properties of the TiO
2 – PS nanocomposite films are studied using the Z-scan technique. Structural properties of the films are investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The optical band gap energy of the TiO
2 – PS films are determined from the optical absorption spectra. The relation between the optical nonlinearities and the bandgap energy, as a microscopic electronic property of the semiconductor nanocomposite, is established. It is shown that an increase in the content of TiO
2 NPs in the nanocomposite films results in bandgap narrowing and concomitant enhancement of optical nonlinearities. It is proposed that bandgap narrowing and enhancement of optical nonlinearities can be ascribed to the introduction of mid-gap states as a result of the formation of surface defects in TiO
2 NPs. The results of this work indicate that incorporation of TiO
2 NPs in the PS polymeric matrix can be a new way for bandgap narrowing of TiO
2 NPs toward the visible light region, which is of great interest for their application in this part of the spectrum. Furthermore, enhancement of the optical nonlinearities of the spin-coated TiO
2 – PS films by increasing the TiO
2 NP content can open up new avenues for their use as nonlinear optical films in photonics applications.
Keywords:
nanostructures, thin films, optical properties, photonics applications. Received: 03.12.2018
Revised: 21.04.2019