Electro-optic sensor for static fields

A sensor has been developed for low frequency and DC electric fields E. The device is capable of measuring fields with \(\varDelta \mathrm{E}= 4\) (1) V/cm resolution. It is based on a Y-cut Z-propagation lithium niobate electro-optic crystal. For a particular commercially available bare crystal, we achieved an in air time constant \(\tau _\mathrm{c}(\mathrm air)= 6.4(1.8)\) h for the decay of the electro-optic signal. This enables field monitoring for several hours. As an application, we demonstrated that a constant electric field \(E^{\mathrm{ext}} = 640\) V/cm applied via external electrodes to a particular spherical glass container holding an Xe/He gas mixture decays inside this cell with a time constant \(\tau _{E}^{\mathrm{glass}} = 2.5(5)\) h. This is sufficient for the needs of experiments searching for a permanent electric dipole moment in \(^{129}\)Xe. An integrated electric field sensor has been constructed which is coupled to a light source and light detectors via optical fibers. The sensor head does not contain any electrically conducting material.