| 摘要 |
PURPOSE:To lower voltage and losses and to eliminate a DC drift without requiring a buffer layer by introducing a 2nd metal ion to decrease the refractive index of a substrate surface into the substrate surface thereby embedding light guides into the substrate. CONSTITUTION:The buffer layer is not formed between transparent electrodes (ITO) 103 and the LiNbO3 substrate 101 and an Mg-diffused layer 104 diffused with the Mg ion is formed on the surface of the LiNbO3 substrate 101. The light guides 102 are formed by diffusing Ti into the LiNbO3 substrate 101 and hereafter, the Mg which is the ion to lower the refractive index of the LiNbO3 substrate 101 conversely from the Ti ion is diffused into the substrate surface. The refractive index direction in the depth direction is then symmetrized and the position where the refractive index is max. can be made as the position of the depth of several mum in the substrate. The embedded guides 102 having the position of the max. light intensity in the depth of several mum in the substrate can be formed by selecting the diffusion depth of the Mg at this time. The voltage required for switching is thus lowered by the effect of removing the buffer layer and the phenomenon of the DC drift is prevented as well. |
