Effect of oxygen pressure on second harmonic generation in zinc oxide thin films deposited by PLD

Nanocrystalline ZnO thin films with c-axis preferred orientation were deposited on glass substrate at different oxygen pressures by a pulsed laser deposition (PLD) method. The microstructures and linear optical properties of the films are investigated by X-ray diffractometry and spectroscopic ellipsometry, respectively. Second harmonic generation in the films is studied using the rotational Maker fringe technique in the transmission scheme. All the ZnO films show second-order nonlinearity and the largest effective nonlinear coefficient d33, which increases with the grain size, is obtained in samples deposited at the oxygen pressure of 2×10−2 Pa. The effects of the oxygen pressure on the microstructure, macrostress and second-order optical nonlinearity are analyzed.