This paper describes non-invasive electro-optic sensors devoted to simultaneous electric field and temperature
measurements. Based on Poeckel's effect, these sensors consist in non-centrosymmetric crystals for which an electricfield
induces a modification of their refractive indices [1]. Such modification can also be induced by a drift of the crystal
temperature [2]. After explanation of the principle, we will illustrate some applications (high power microwave
characterization, bioelectromagnetism, electric field mapping of high voltage devices) for which electro-optic sensors
give excellent performances. These sensors perform vectorial E-field measurement (modulus and phase of each E-field
components) with both high spatial and temporal resolutions. As they are pigtailed, long distance remote sensing is then
allowed. They are also non-invasive due to their fully dielectric design. However, their sensitivity remains quite low for
electromagnetic compatibility and their size remains too important for bioelectromagnetism studies in Petry dishes for
example. So, two ways of improvement are pursued. The first one consists in using Fabry-Perot microcavities based on
LiNbO3 optical waveguide to dramatically reduce sensors size. The second one consists in an optical processing (optical
carrier rejection) of the laser probe beam to increase the sensor sensitivity for high frequency measurements. We will
present first results concerning these improvements and also results that have been performed in free space with a fully
automated setup in both frequency and time domains.
KEYWORDS: Crystals, Modulation, Temperature metrology, Dielectric polarization, High power microwaves, Laser beam diagnostics, Birefringence, Sensors, Transducers, Refractive index
The EO probe developed, offers an accurate evaluation of only one component of either continuous or single
shot electric signal as long as the electric field to be measured is strong enough. Since those probes are also non
intrusive, very small (tens of microns width) and have a flat response over a very large bandwidth (more than
seven decades), they are competitive candidates for accurate vectorial measurement of either radiated or guided
high power microwave electric field in the far- and near-field region. Unfortunately what makes them so versatile
is also their Achilles' heel: the strong temporal instability of their response. Therefore, we present, in this paper,
a fully-automated electro-optic probe developed to stabilise the transducer.
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