Non-linear absorption and second harmonic imaging of Zn–BaTiO 3 thin films prepared by laser ablation

Abstract

Zinc-doped barium titanate samples have been prepared on Corning glass as well as on silicon wafer by laser ablation. Samples on glass having different deposition time and varying zinc oxide content have been studied by Z-scan technique at a wavelength of 540 nm and laser intensity of 20 GW while samples on silicon have been characterized by second harmonic (SH) imaging as a function of zinc content. The result on Z-scan measurements shows that films doped with 1 wt.% ZnO and deposited for a period of 80, 100 and 180 min respectively exhibit non-linear absorption with the maximum non-linear absorption coefficient ( β max) of 800 cm/GW. The undoped as well as samples of BaTiO 3 doped with 3, 4 and 5 wt.% ZnO with deposition time of 60 min each exhibit non-linear saturation with the sample containing 5 wt.% ZnO having the lowest value of − 5.9 × 10 2 cm/GW, which signifies that an increase in zinc oxide content leads to a reduction in the observed bleaching effect. In addition, it is also suggested that switching from non-linear absorption to non-linear saturation is probably due to thickness effect. The SH imaging has shown the location dependence of the films, which we assume may be due to the geometry of the deposition module and crystal growth through the formation of small crystallites as the building block of the films.