| 摘要 |
PURPOSE:To increase the threshold value, to improve the work efficiency, and to reduce the optical transmission loss by heating an x- or z-cut lithium niobate or lithium tantalate crystal substrate in carboxylic acid to form a surface layer having a higher refractive index. CONSTITUTION:One side of an x-cut LiNbO3 crystal substrate 1 is polished. The substrate is subjected to successive ultrasonic washing with acetone and pure water and it is dried by blowing gaseous nitrogen. The substrate is put in a beaker contg. carboxylic acid with the polished side upward. The beaker is placed in a heating furnace, where ion exchange is carried out by heating to form a layer 2 having a higher refractive index. Thus, a thin film type optical waveguide is obtd. The coloring and roughening of the surface of the crystal substrate are not caused, and no deposite sticks to the surface. |
