| 摘要 |
PURPOSE:To lower a driving voltage, to increase a modulation speed, and to reduce the size of an element by realizing the thin-film structure of the element, and utilizing periodic static elastic strain. CONSTITUTION:On an Y-plate X-propagation lithium niobate substrate 1, a metal diffusion type optical waveguide 2 is formed, and on it, a reed screen type silicon dioxide film 3 is formed. Consequently, residual stress generated when a reed screen type pattern 3 is formed and a difference in coefficient of thermal expansion between the material of the optical waveguide 2 and that of the pattern 3 are utilized to generate periodic static elastic strain on the optical waveguide 2. Therefore, when the Bragg's phase condition ¦betaE-betaM¦=2pi/lambda where betaE and betaM are the propagation constants of mode TE and TM is satisfied, conversion between the modes TE and TM is performed. Further, an aluminum electrode 4 is provided and applied with a voltage to vary a mode conversion rate. |
