| 摘要 |
PURPOSE:To improve the loss characteristic and crosstalk characteristic of an optical circuit by partially controlling the shape of the refractive index distribution of light guides thereby controlling the shape of the refractive index of only the desired part without deteriorating the characteristics of the other parts simultaneously integrated on the same substrate. CONSTITUTION:The light guides 303, 304 are formed by diffusing Ti having the action to increase the refractive index into the LiNbo3 substrate 301 and thereafter Mg to decrease the refractive index is diffused into the substrate to form the input and output light guide parts 305, 307. The refractive indices are thereby distributed to such a shape where the refractive index is largest in the position deep at 3-4mum from the substrate surface and is approximately symmetrical before and after said position. The light intensity distribution of exit light is thus made symmetrical in the direction perpendicular to the substrate by further diffusing MgO into the substrate after the diffusion of MgO. Since the MgO is diffused after the diffusion of the Ti, the change of the concn. distribution of the Ti in the diffusion stage of the MgO is worried but the diffusion rate of the Mg is much higher than the diffusion rate of the Ti and therefore,the refractive index distribution is made to the desired shape by the diffusion of the Mg with substantially no influence on the concn. distribution of the Ti. |
