Effect of lanthanum doping on linear and nonlinear-optical properties of Bi 3TiNbO 9 thin films

Abstract

Lanthanum doped Bi 3TiNbO 9 thin films (LBTN- x, La 3+ contents x = 5%, 15%, 25% and 35 mol.%) with layered perovskite structure were fabricated on fused silica by pulsed laser deposition method. Their linear and nonlinear optical properties were studied by transmittance measurement and Z-Scan method. All films exhibit good transmittance (>55%) in visible region. For lanthanum doping content are x = 5%, 15% and 25 mol.%, the nonlinear absorption coefficient of LBTN- x thin films increases with the La 3+ content, then it drops down at x = 35 mol.% when the content of La 3+ in (Bi 2O 2) 2+ layers is high enough to aggravate the orthorhombic distortion of the octahedra. We found that, 25 mol.% is the optimal La 3+ content for LBTN- x thin films to have the largest nonlinear absorption coefficient making the LBTN- x film a promising candidate for absorbing-type optical device applications.