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 $$\varDelta \mathrm{E}= 4$$ΔE=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 $$\tau _\mathrm{c}(\mathrm air)= 6.4(1.8)$$τc(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 $$E^{\mathrm{ext}} = 640$$Eext=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 $$\tau _{E}^{\mathrm{glass}} = 2.5(5)$$τEglass=2.5(5) h. This is sufficient for the needs of experiments searching for a permanent electric dipole moment in $$^{129}$$129Xe. 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.