| 摘要 |
PURPOSE:To decrease frequency dispersion and to enable modulation up to extra-high frequencies by using a superphotoconductor as an electrode material in order to change the coupling constant between two light guides by an electro- optic effect. CONSTITUTION:The conventional normal conductor is changed to a superconductor and is then used as a microwave strip line 23 which constitutes a part of an optical modulator. The oxide superconductor of a recently discovered La-Ba-Cu-O system or Y-Ba-Cu-O system which is a ceramic system of the critical temp. Tc=90K class grows as a single crystal on a perovskite type dielectric substrate (for example, SrTiO3 or LiNbO3), etc.). The microwave strip line 23 formed of the superconductor is the extremely small frequency distribution to frequencies below the gap energy intrinsic to the superconductor and has the excellent capability as the transmission line for extra-high frequencies. For example, the oxide superconductor of the Y-Ba-Cu-O system has 30meV gap energy and is capable of transmitting the extra-high frequencies up to about 10<12>Hz; therefore, the light modulation by the extra-high frequencies in 10<12>Hz order is possible. |
