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

研究了一种采用高增益超导升压电路的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一种中心频率为lOGHz、带宽为5MHz、电压增益为33dB的电压放大器。并在LiNbO_3光波导上进行了YBCO电极在MgO衬底倒装芯片上的初步实验。(1)采用带共面波导（CPW）传输线的电路模型（传输线模型）研究升压电路的增益，利用电磁波（EM）模拟器设计出电压增益为33 [dB]的实用器件。(2)为了验证提出的设计理论，我们进行了实验。我们展示了由YBCO薄膜在尺寸为10 [mm] × 10 [mm]的MgO衬底上制作的曲线形3极切比雪夫滤波器调制电极的图案。将MgO衬底上的YBCO电极倒装键合到LiNbO_3衬底的光波导上，并用冰箱冷却。我们给出了观察到的器件S11的群延迟。观测到的数据发现了理论所期望的痕迹。

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.