Optical mode size control by MgO indiffusion in Ti:LiNbO3 waveguides

In this paper, the use of magnesium oxide (MgO) indiffusion in combination with Ti:LiNbO<sub>3</sub> through appropriate control of pre- and post-diffusion parameters is investigated as a way of controlling optical mode size. The co-diffusion of pre-patterned Ti with various patterned MgO films on LiNbO<sub>3</sub> has been compared experimentally. This method has been applied to study straight waveguides and couplers. The waveguides were optically characterized by near-field mode size and loss measurements methods at a wavelength of 1.55 μm. Reduction of inter-mode coupling between adjacent waveguides with the introduction of MgO has been observed