Development of optical isotropic E-field sensor operating more than 10 GHz using Mach-Zehnder interferometers

An electric field sensor using Mach-Zehnder interferometers has been designed to operate at more than 10 GHz. The velocity of the optical wave on the waveguide is investigated to determine the electrode length, and the characteristics of frequency response are analyzed using the moment method to determine the sensor element length. The electrode length of 1 mm and the element length of 8 mm are settled by these investigations. An isotropic electric field sensor is constructed using three sensors. The minimum detectable electric field strength is 22 mV/m at frequency bandwidth of 100 Hz. This is about 100 times for the conventional electric field sensor using a similar element. The sensitivity deviation is within 3 dB when temperature changes from 0 degree to 40 degree. The deviation of directivity can be tuned within ±1 dB to calibrate the sensitivity of each element. The sensitivity degradation is within 6 dB up to 5 GHz and within 10 dB up to 10 GHz. This is almost in agreement with the calculated results. The sensor can measure almost the same waveform as the applied electric field pulse whose width is 6 ns and rise time is less than 2.5 n