Single shot measurements of the E-field vector with pigtailed optical probes
Summary form only given. Over the variety of available sensors dedicated to electric (E)-field characterization, the use of antennas constitutes the most widespread technique. While such probes are convenient and provide a good sensitivity, they remain invasive and bandwidth limited. At the opposite, fibered electro-optic transducers1 are fully dielectric, millimeter sized and allow to perform measurements of the E-field vector from DC to several gigahertz and even up to terahertz frequencies using equivalent-time sampling. Furthermore, recent developments lead to a simultaneous characterization of 2 transverse E-field vector components with a single EO probe2. Based on polarization state modulation, the EO transducer is linked to a remote (up to 30 meters) optoelectronic set-up including a ultra low noise laser feeding the probe and a real time optical set-up to manage the modulation treatment. The automated and servo controlled measurement bench is temperature dependent free. The available measurement dynamics exceeds 100 dB, ranging from less than 1 V. m-1. Hz-1/2 up to the breakdown electric field in air.An exhaustive comparison between BO sensors and other technologies will be firstly given during the conference. This analysis will be based on intrinsic sensor properties, such as sensitivity, frequency bandwidth, vectorial selectivity, spatial resolution and induced perturbation on the field to be measured. After recalling the principles of the BO effect, the optical arrangement of the optical probes will be described. The characterization of the BO system will be presented together with experimental results illustrating the potentialities of BO sensors. Among these examples, measurements of pulsed B-field in air (pulsed power), water (specific absorption rate evaluation in pulsed regime) or in plasma (real time evolution of the electrical discharge associated B-field) will be shown.
Electro-optic sensors for electric field measurements. II. Choice of the crystals and complete optimization of their orientation
We present a simple method to determine both direction of the electric field component to which an electro-optic sensor is sensitive and sensitivity to this component. For this purpose we introduce the concept of an electro-optic sensitivity vector. This work is done for electro-optic sensors working as amplitude modulators, as phase modulators, or as polarization state modulators. The method applies to any anisotropic crystal, regardless of crystallographic group. After defining three kinds of electro-optic sensor geometry that allow longitudinal, transversal or fully vectorial electric field probing, we make a comparative study of several commonly used electro-optic crystals. We derive the optimal orientations of the crystals with respect to the optical probe beam that lead to high-performance electro-optic sensors. We also treat isotropic crystals in the case of polarization state modulators. In contrast to anisotropic crystals that are sensitive to a unique electric field component, we show that isotropic crystals are sensitive to two orthogonal electric field components simultaneously.
Electro-optic sensors for electric field measurements. I. Theoretical comparison among different modulation techniques
We present a complete analysis of electro-optic sensors for electric field measurement based on three different modulation techniques: amplitude, phase, and polarization state modulation. We treat the most general case, considering both isotropic and anisotropic crystals and taking into account the absorption of the crystal. We derive the optimal configuration of experimental setups for the three studied modulation techniques, and we give the values of the variable physical parameters required to yield the best performance. Finally we compare the three modulation techniques and show that phase or polarization state modulations result in exactly the same performance while amplitude modulation gives slightly enhanced performance.