Gwenaël Gaborit

Vectorial electric field measurement using isotropic electro-optic crystals

The authors present a two-component electric field measurement using a single electro-optic crystal and a single laser probe beam. This vectorial electric field measurement based on polarization state modulation is possible using isotropic electro-optic crystals for which directions of the eigendielectric axes are directly linked to the direction of the applied electric field. The proposed method can be used either for continuous wave or single shot measurements as the two electric field components are measured simultaneously.

Electric field and temperature measurement using ultra wide bandwidth pigtailed electro-optic probes

We present pigtailed electro-optic probes that allow a simultaneous measurement of high frequency electric fields and temperature using a unique laser probe beam. This has been achieved by the development of a novel probe design associated with a fully automated servo-controlled optical bench, initially developed to stabilize the electric field sensor response. The developed electro-optic probes present a stable response in outdoors conditions over a time duration exceeding 1 h, a frequency bandwidth from kHz to tens of GHz with a sensitivity of 0.7 Vm(-1)Hz(-(1/2)), and a temperature accuracy of 40 mK.

Single Shot and Vectorial Characterization of Intense Electric Field in Various Environments With Pigtailed Electrooptic Probe

In this paper we illustrate the ability of electrooptic sensors to perform electric (E)-field vectorial measurements. Thanks to their frequency response spreading over nine decades and to their measurement dynamics reaching 120 dB, these sensors are of high interest for some applications (near field mapping, energy line monitoring, electromagnetic compatibility, and so on). Furthermore, due to their fully dielectric structure and millimetric size, almost no perturbation is induced on the E-field to be measured, even in the near field region. This paper is focused on high-intensity pulsed E-field characterization in different environments such as air, water (bioelectromagnetism applications), or plasmas (in situ assessment of the E-field associated to an electric discharge and to the induced plasma). The use of such a technology for electrical equipment and energy line monitoring is also investigated.

High-finesse Fabry-Perot electro-optic sensors with enhanced sensitivity and high spatial resolution

We present a high-finesse optical cavity containing a LiTaO(3) electro-optic crystal, devoted to free-space electric field characterization. Theoretical considerations will show that the modulation depth is directly related to the transversal components of the field to be measured, thus opening the way to vectorial mapping of the electric field using a single electro-optic crystal. Also, a discussion about noise and sensitivity will be given. As the latter increases with the effective cavity length, and bandwidth decreases, a trade-off is realized, allowing us to measure an electric field of 60 mV/m/ sqrt[Hz] in a 110 MHz bandwidth. Cavity dimensions are less than 8 mm(3), giving an inner-crystal transverse spatial resolution of 70 microm and allowing pigtailed systems to integrate.

Contactless, Real Time, and Vectorial Inspection of a Multiwire Power Cable Voltage Using an Electro-Optic Technique

Here, we demonstrate the suitability of the electro-optic technique for contactless monitoring of a power cable composed of several conductors. We have developed an electrometer performing real-time characterization of the field surrounding the cable. The electrometer gives the transient evolution of the field strength as well as the field orientation. The actual transverse field vector associated with a three-phase cable follows ellipses. These ellipses have been assessed with an analytical approach, finite difference time domain simulations, and also experimentally with the electro-optic electrometer.

Packaged optical sensors for the electric field characterization in harsh environments

This paper describes the performances of electro-optic sensor dedicated to electric field vectorial measurements. It demonstrates the crucial importance of the sensor packaging constitution and geometry to provide a reliable assessment of the E-field vector. The influence of the environment on the sensor response is also analysed.

Sensing Microwave Guided or Radiated Electric Field by Means of Vectorial Electro-Optic Sensors

This paper describes firstly the design and the characterization of pigtailed electro-optic (EO) sensors based on Pockels effect, particularly appropriate for non invasive electric (E) field measurements. Afterwards we present transient and frequency characterization of a microwave guided field. Last experiments concern the ability of EO probes to measure a non recurring single shot microwave field compared to antennas. We also provide an assessment of the disturbance induced by the sensors to the field to be measured, using an infrared thermography technique. Sensors based on polarisation state and on amplitude modulation will be presented and compared to alternative techniques during the conference

Longitudinal Electro-Optic Probe for the Transient Analysis of the Radial Field Surrounding a Three-Phase Cable

In this paper, we present the potentialities of the electro-optic technique for the radial electric field transient analysis of a three-phase power cable. A longitudinal electro-optic probe performing real time characterization of the field surrounding the cable has been developed. The measurement gives the transient evolution of the radial component of the field. The analysis provides information on amplitude, position, and phase of the conductors in the multicore cable. Theoretical analysis, simulations, and experimental measurements are in agreement and demonstrate the contactless voltage diagnostic of multicore cables.

Spatio-temporal and vectorial analysis of the electric field vector with an optical sensor

The ability of an electro-optic system is here demonstrated for the mapping of the electric field vector over a wide bandwidth. Thanks to their dielectric structure, such sensors are intrinsically very low invasive and allow to perform near field analysis. Even in the reactive area of radiative devices, the probe allows to characterize the field vector distribution with a dynamics exceeding 120 dB. The associated spatial resolution is weaker than 500 μm and the measurement bandwidth reaches more than 10 GHz.

Electro-optics as a versatile technique for non-invasive vectorial sensing of electric fields

We here present the most recent advances in electro-optics (EO) dedicated to non-invasive characterization of electric (E) fields. We develop E-field sensors exploiting the Pockels effect (E-field induced linear variations of refractive indices for EO crystals). These pigtailed transducers are fully dielectric. While the sensitivity reaches 1 V.m−1. Hz−1/2, the bandwidth covers more than 8 decades of frequency. The spatial resolution is greater than 100 μm. A complete analysis of these sensors will be presented as well as some examples in different research areas: 2D mapping of guided waves, transient evolution of disruptive E-Field, SAR measurements in biologic media, …