STUDY ON WAVEGUIDE-TYPE ELECTRIC-FIELD SENSOR USING NONLINEAR POLYMER FOR PRECISELY MEASURING ELECTROMAGNETIC NOISES.

近年来，随着个人计算机等电子设备的普及和高速运行，宽频带的电磁波噪声会影响到其他电子设备，有时还会导致误操作。然后，我们研究了一种宽带电场传感器来精确测量电磁噪声。该传感器由一个宽带平面小天线和一个采用非线性聚合物的宽带光调制器组成，分析和设计了一种有望成为宽带的小平面蝶形天线。结果表明，该天线比平面偶极子天线具有更宽的带宽，并且在90°的蝴蝶结角度下达到最宽。设计了一种光波导调制器，其光波导材料为波长色散小的侧链型非线性聚合物3RDCVXY，并采用简单共面波导。为了用光漂白的方法制作通道光波导，我们测量了紫外光照射下的折射率降低，证实了折射率随时间的下降是稳定的。我们可以设计出光波与调制微波之间既有阻抗匹配又有速度匹配的调制器。结果表明，在相互作用长度为2 cm时，设计的调制带宽为496 GHz，此时带宽仅由共面波导的传输损耗决定。制作了设计的共面波导，并对损耗进行了测量。此时测得的损耗超过10分贝/厘米，并且在相互作用长度为2厘米时的带宽为30 GHz。我们计划改进制作方法和传输损耗，使其接近设计的带宽。

Recently, accompanied with the popularization and the higher speed operation of electronic equipments as personal computers, electromagnetic wave noises with wide frequency range affect other electronic equipments and occasionally lead to mis-operation. We then study a wideband electric-field sensor to measure precisely the electromagnetic noises. The sensor is composed of a wideband planar small antenna and a wideband optical modulator using a nonlinear polymer.We analyze and design a small planar bow-tie antenna which is expected to be wideband. It is seen that the antenna has wider bandwidth than a planar dipole antenna, and it becomes the widest at a bow-tie angle of 90 deg. Furthermore, an antenna that each side opposite to the knot of the bow-tie change from, a straight line to an arc, has much wider bandwidth.We design an optical modulator in which the material of optical waveguide is the side-chain type nonlinear polymer,3RDCVXY with small wavelength dispersion, and the simple coplanar waveguide (CPW) is used. To make channel' waveguides with the photobleaching method, we measured the decrease in refractive index by uv exposure and confirmed that the decrement is stable with time. We could design the modulator with both the impedance matching and the velocity matching between the optical wave and the modulating microwave. As the result, we obtain the designed modulating bandwidth of 496 GHz at an interaction length of 2 cm.At this condition the bandwidth is decided only by the propagation loss of the CPW. We made the designed CPW and measured the loss. The measured loss is over 10 dB/cm at this time, and the large loss suggests a bandwidth of 30 GHz at an interaction length of 2 cm. We plan to improve the fabrication method and the propagation loss to go near the bandwidth to the designed one.