Development of wide-band and highly sensitive electric field sensor using LiNbO3 optical modulator

A Mach-Zehnder interferometer whose half-wave voltage is about 4 V and a YAG laser pumped by a laser diode whose output power is 25 mW are used to improve the sensitivity of a LiNbO₃ electromagnetic field sensor. The resulting frequency response is almost flat from 100 Hz to 300 MHz and the minimum detectable electric field strength is 1 mV/m at 50 MHz and 0.14 mV/m at 750 MHz. The frequency response of the sensor is analyzed using the moment method, and the calculated results agree with the measured results. The improved sensor can measure an electromagnetic impulse whose peak value is larger than 10 V/m and width is wider than 5 ns