| 摘要 |
PURPOSE:To widen the modulation band of the modulator by a simple process by forming a space part near the outside of an electrode for signals along the longitudinal direction thereof. CONSTITUTION:An earth electrode 3b and the electrode 3a for signals are formed via a buffer layer 4 on a lithium niobate substrate 11 on which light guides 2 are formed. The space part 11a is provided near the outside of the electrode 3a for signals along the longitudinal direction thereof. An air layer of a small dielectric constant is, therefore, provided by this space and the effective refractive index of the microwaves propagating in the electrode 3a is lowered by as much as the space part 11a and is approximated to the refractive index of the light waves propagating in the light guides 2. As a result, the speed difference between the light waves and the microwaves is decreased and the modulation speed is increased. The modulation band is thus widened by using the simple production process. |
