Enhanced second-order nonlinear optical response of LiNbO3 films upon Er doping

Erbium-doped LiNbO3 films have been produced in a single-step process by alternate pulsed laser deposition. The dopant is incorporated in submonolayers whose nominal indepth separation is varied in the range 1.7-4.0 nm to lead respectively to Er concentrations in the range 3.4-0.6x10(20) atoms/cm(-3). All the films exhibit the characteristic Er3+ photoluminescence at 1.54 mum with lifetime values as high as 3 ms. The d(33) nonlinear coefficients determined from second-harmonic generation experiments are in the range 22-28 pm/V, the films having nominal Er submonolayer indepth separation of 3-4 nm exhibiting d(33) values slightly above that of the bulk material. The comparison of the d(33) values obtained in the Er-doped films to those reported earlier for similar undoped films shows clearly that both the structural quality and the second-harmonic performance of the films can be enhanced by Er doping. (C) 2002 American Institute of Physics.