Application of superconducting striplines to traveling-wave type LiNbO/sub 3/ optical modulator

The performance of a traveling-wave-type LiNbO/sub 3/ optical modulator with superconducting electrodes has been studied theoretically and experimentally. In the case of velocity matching between signal and optical waves using a shielding plane on top of the coplanar stripline, numerical calculations of the attenuation constants of both superconducting and normal-conducting striplines indicate that the performance of the optical modulator is expected to be much superior to that using normal metals with respect to the figure of merit of bandwidth/driving power. Low-temperature operation of the optical modulator with superconductor electrodes has been demonstrated in the temperature range between 4.2 K and 300 K for DC signals as well as microwave signals at frequencies from 8 GHz to 12 GHz. It was shown that the modulation voltage was not very sensitive to temperature variation.<>