POTENTIAL SENSOR AND POTENTIAL MEASURING METHOD USING ELECTROOPTIC CRYSTAL

摘要

PURPOSE:To eliminate the deterioration of the electrooptic crystal and to detect a potential with high accuracy by forming a high-resistance compound semiconductor by epitaxial growth on a compound semiconductor which is made low in resistance by doping impurities by utilizing the birefringence of the compound semiconductor. CONSTITUTION:A semiconductor wafer which is doped with impurities of proper density is used as the low-resistance compound semiconductor. On this semiconductor, the high-resistance compound semiconductor is formed by epitaxial growth. Consequently, the crystal axis of the epitaxial grown layer which has extremely excellent surface accuracy is set automatically to the best value. As an example of potential measurement by this sensor, the linear polarized light from a laser diode 20 is passed through a condenser lens 21 and a half- mirror 22 to irradiate the sensor 10. The sensor 10 varies in optical anisotropy with the potential of a body 24 to be measured to generate elliptically polarized light, which is split into two by a splitter 26; and they are detected by photodetecting elements 29 and 30 and amplified 31 to detect signal components from which variation is removed.