Optical high-sensitive field sensor using a Pockels crystal

The sensitivity of an optical field sensor with a Pockels crystal of LiNbO3 for measuring a field distribution in a long-gap discharge has been much improved by using an intensity difference method with an intensity-modulated laser beam. The signal-to-noise ratio (S/N) is also improved by 37 dB from that without the above-mentioned method. The resultant sensitivity of the new field measuring system is 100 times higher than that of the previous one. Finally, it is possible to measure an electric field down to 7.5 V/cm in the long-gap discharge with high accuracy corresponding to the S/N ratio of 20 dB and 1.5 V/cm with the accuracy of 6.0 dB.