Nonlinear optical properties of Bi0.5Na0.5TiO3 thin films grown by PLD.

The present work investigates the role of oxygen partial pressure (PO 2) during the thin film growth in obtaining phase and controlling the crystallinity and optical responses in the thin films. Rietveld refinement of X-ray diffraction confirmed a rhombohedral structure of BNT as a major phase with secondary phase of Bi 2 Ti 2 O 7 and Bi 4 Ti 3 O 12. The diminutions of the secondary phase are observed with an increase in PO 2 , which signifies the crystal structure closely related to the partial oxygen pressure. The refractive index of films was found to be improved and optical bandgap energy was reduced with PO 2 due to the increase in crystallinity as well as decrease in oxygen vacancies. Nonlinear optical properties show a strong PO 2 dependency, self-focusing behaviour with a positive, large optical nonlinearity (n 2 = 4.62 × 10−6 cm2/W) and strong absorbance (β = 0.755 cm/W) for the film deposited at 10 Pa, which makes a potential candidate for the nonlinear photonic device applications. [ABSTRACT FROM AUTHOR]