Electric field probe based on electro-optic technology

Based on Pockels effect and after 15 years of research and development, Kapteos is proud to propose this high-end electro-optic technology to our worldwide market. This technology offers the highest possible performances to measure electric fields in almost any harsh environments. Kapteos, as an expert in terahertz and electro-optic technologies, is constantly improving the proposed systems, accessories, services, …

Do not hesitate to contact us to evaluate your specific needs in terms of electric field measurements even you do not see the right system in our portfolio.

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Main features of Kapteos electro-optic technology for electric fields

Main features

  • Vector E-field: 3 axis + phases
  • Frequency bandwidth: 10 Hz to 100+ GHz with sub-nanosecond temporal resolution
  • Dynamic range: 50 mV/m to several MV/m
  • Max E-field: > 10MV/m without damage
  • Spatial resolution: < 1 mm
  • Multi media: air, liquids, gas, vacuum
  • Compactness: 5 * 35 mm sensing probe
  • Non-invasive: no metal => no impact on E-field
  • Selectivity: > 50 dB
  • Sensitivity: 50 mV/m/√Hz (air, longitudinal probe)
  • Near field: down to 0 mm distance
  • Max B-field: withstand more than 4.7T
  • Operation temperature: 0 to 50°C (probe)
  • AF correction: automatic and real-time
  • Remote distance: up to 100 meters
  • Easy installation: set-up ready in < 5 min

Principle of electro-optic technology based on Pockels effect

Electromagnetic measurement systems composed of eoSense opto-electronic converters on the one hand and on eoProbe optical probes on the other hand are based on Pockels effect. This latter effect occurs in some optical crystals, called electro-optic (EO) crystals, and manifests itself as an E-field induced modification of the principal dielectric axes of the EO crystal. An EO crystal behaves like a waveplate for a laser beam passing through it. Under applied E field, the dephasing induced by the waveplate is modified in proportion to the field strength. This occurs through the E-field induced variation of the refractive indices of the EO crystal. For a comprehensive description of the use of Pockels effect in E field sensors, the reader may refer to J. Opt. Soc. Am. B Vol. 19, pp 2704-2715 (2002).

Electro-optic technology based on Pockels effect

Comprehensive measurement of the E-field vector

The electro-optic technology allows to measure the 3 components and the phase of a vector electric field. This is also the case for Kapteos probes. The 3 axis of the vector are clearly measured independently thanks to the eoSense opto-electronic converter and the longitudinal and transverse probe types. On top of that, Kapteos accessories facilitate the physical installation setup of probes to operate an easy and repetitive measurement.

Comprehensive electric field in plasma application

Non invasive measurement

The design of the probe does not integrate metal parts. The active part of the sensor is based on cristal. The measured signal is transmitted by a laser inside a fiber optic link. The major advantages of this design are :

  • The measured electric field is not disturb unlike the classical antenna based probes
  • The probe and the opto-electronic converter may be separated up to 100 meters :
    • With extreme low losses particularly in the GHz frequencies
    • To ensure correct measured without being impacted by radiated fields

The pictures below  (collaboration with Creatis) show measurements of electric fields inside animal tissuesfruits or vegetables inside an MRI system.
Leaving the mouse over the pictures will stop the slider.

More than 130 dB of dynamic measuring range

Electro-optic probe linearity curve with 130 dB

With a theoretical limit of 140 dB dynamic range, Kapteos has demonstrated with several tests the capability for the eoProbe to have a dynamic range just above 130 dB which is much more than you would need in any kind of application. The dynamic range is the ration in dB between the maximum allowed E-field divided by the minimum allowed E-field.

The technology has also proven that, over a dynamic range of 120 dB, repetitive measurements even at different moments, the absolute values stay within a tolerance better than ± 0.25 dB. Electro-optic technology is a technology you can trust.

8 decades frequency bandwidth and ultra fast response

It has been demonstrated via several tests and international publications that the electro-optic technology can measure electric fields up to several terahertz (THz) in either frequency domain or time domain. This is of importance when the applications requires to measure typically a very narrow single pulse like for example nano pulse generators for food sterilization or Electromagnetic Pulses (EMP) used by defense organisations. Kapteos probes can, without any difficulties, measure continuous waves or any other wave forms. Measurements performed at IMEP-LAHC lab, Université Savoie-Mont-Blanc.

Insulated probe to ensure safe measurements

Fully insulated electric field probe

Thanks to the design based on electro-optic technology, the probe is metal-free. The measured signal is transmitted to the opto-electronic converter via a fiber optic link. These are perfect conditions to ensure a good insulation between the DUT (Device Under Test) and our probe. That’s why it is possible, in some cases, to measure the electric field at a very short distance (few millimeters) or even directly in contact with the DUT. When security matters!

Sub-millimeter spatial measurement resolution

Some applications requires very precise localisation of the measured field like patch antennas, specific absorption rate assessment, EMC, … The spatial resolution is the smallest distance between two steps of measurements placed next to each other. This resolution is linked to the physical dimension of the laser beam: 0.6 mm. So if the probe moves of 0.6 mm (x or y axis), a new electric field measurement can be made. Kapteos indicates a resolution of 1 mm to be valid in all cases. This spatial resolution should be more than enough for most of the applications.

Electric field mapping

More than 50 dB of selectivity

Measurement showing selectivity of emf probe

An essential feature related to vector E-field measurements concerns the ability of measuring a given E-field component while rejecting the orthogonal ones. Kapteos probe allows a rejection ratio of more than 50 dB (more than 99.7%) which is more than enough for most of applications. The curve shows that the position of the concerned axis must placed quite accurately to ensure this high selectivity.

This feature is of importance for transverse probe type (ET… and not EL…). To ease the probe setup, the transverse probes have an arrow. This arrow must be placed in accordance with the electric field orientation. See FAQs on probe for more details (How can I make sure the probe is correctly oriented in accordance with the axis of the component of the E-field to measure?).


Real-time antenna factor correction for stable measurements from 0 to +50°C

This high-end advanced feature allows to measure the absolute value of the electric field with an exceptional stability whatsoever the temperature variations, the hook-up losses, the duration of the measure which could be days. This compensation is performed in real-time by the eoSense opto-electronic converter. This is a compulsory feature when repetitive electric field measurements must be performed at different steps or over a long period of time.

The Antenna Factor variation on the right picture lies within 1% without any correction.

Automatic Antenna Factor correction