Optical operation by electrooptical features of ZnO nanocrystalline films doped by Tm3+ ions

Highlights: ► High quality ZnO:Tm3+nanocrystalline films were grown. ► Photoinduced electrooptical changes were observed under influence of bicolor laser treatment. ► Relaxation processes are completely reversible after about 600 s. - Abstract: The photoinduced linear electrooptical effect was measured using the bicolor laser light between the fundamental 10 ns Nd:YAG laser beam and its green doubled frequency. The optimal ratio of intensities between these two beams was equal to 5:1. As a probing beam, it was used cw 12 mW He–Ne laser beam and Senarmont method was used for detection of the birefringence with accuracy of 10−6. The studies were done on zinc oxide nanocrystalline films doped by Tm3+ ions. Maximal linear EO changes were obtained at minimal Tm3+ content equal to about 0.1% in weight units. With the further increase of the photoinducing beam the observed EO effect enhancement is not so evident and for the 0.5% of Tm3+ the effect disappears at all times during the illumination. The obtained results show that a principal role of localization of the rare earths in the observed effects may be a consequence of formation of the charge density non-centrosymmetry which is crucially dependent on the Tm3+ content in ZnO films.