Broadband and Low Driving-Voltage LiNb0_3 Optical Modulator with High Tc Superconducting Transmission Line

研究了采用高增益超导升压电路的副载波光传输用LiNbO_3光调制器的设计和性能。基于一种新的高增益升压电路设计理论，利用电磁波模拟器设计了中心频率为10 GHz、带宽为5 MHz、电压增益为33dB的电压放大器。在LiNbO_3光波导衬底上进行了YBCO电极的初步实验。(1)采用共面传输线(CPW)传输线模型(传输线模型)研究了升压电路的增益，利用电磁波(EM)模拟器设计了电压增益为33[dB]的实际器件。(2)为了验证所提出的设计理论，我们进行了实验。给出了用尺寸为10[mm]×10[mm]的YBCO薄膜在氧化镁衬底上制作的曲线型三极切比雪夫滤光片调制电极的图形。将氧化镁衬底上的YBCO电极倒装键合在LiNbO_3衬底的光波导上，并用制冷机进行冷却。给出了器件S11的群延时观测结果。观测数据发现了与理论预期相符的痕迹。

Design and performance of a LiNbO_3 optical modulator for subcarrier optical transmission employing a high gain superconducting booster circuit have been studied. Based on a new design theory for the high gain booster circuit, we designed a voltage amplifier with center frequency of lOGHz, bandwidthof 5MHz, and the voltage gain of 33dB using anelectromagnetic wave simulator. A preliminary experiment with YBCO electrode on MgO substrate flip chip bonded on LiNbO_3 optical waveguide has also been made.(1) We study the gain of the booster circuit using the circuit model with coplanar waveguide (CPW) transmission lines (transmission line model), design the practical device with the voltage gain of 33 [dB] by the electromagnetic wave (EM) simulator.(2) In order to confirm the proposed design theory, we carried out the experiment. We show the pattern of the modulation electrode with the meanderline 3-pole Chebyshev filter fabricated by a YBCO thin film on a MgO substrate with the dimension of 10 [mm] x 10 [mm]. The YBCO electrode on MgO substrate was flip-chip bonded onto an optical waveguide in a LiNbO_3 substrate, and was cooled down by a refrigerator. We show the observed group delay of S11 of the device. The observed data find traces of those expected from theory.