Maxime Bernier

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.

Fully Automated E-Field Measurement System Using Pigtailed Electro-Optic Sensors for Temperature-Dependent-Free Measurements of Microwave Signals in Outdoors Conditions

We present, in this paper, pigtailed electro-optic sensors dedicated to the measurement of high-power microwave signals in outdoors conditions. We give results on high-power microwave single-shot pulses obtained with long fiber links (> 20 m) in hard environmental conditions (temperature variations up to 30degC). In these awkward outdoors conditions, we obtain very stable measurements with rms signal fluctuations lower than 0.2 dB. We focus here especially on the design of the temperature-dependent-free system.

Terahertz encoding approach for secured chipless radio frequency identification

In this article, we present a new family of chipless tags, which permit encoding of digital data in the terahertz domain. These devices consist of stacked dielectric media whose thicknesses are of the same order as terahertz wavelengths. Since the information is encoded in the volume of these multilayer terahertz tags, they can easily be associated with classical identification techniques (e.g., barcode, radio frequency identification), where information is encoded at the surface of the tag, to provide higher data security. The principle of this encoding approach is studied and experimentally demonstrated in this paper. A 2 bit tag prototype has been realized and measured for validation purposes.

Electro-Optic Sensors Dedicated to Non-Invasive Electric Field Characterization

This paper describes non-invasive electro-optic sensors devoted to simultaneous electric field and temperature measurements. Based on Poeckels 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.

Determining the Complex Refractive Index of Materials in the Far-Infrared from Terahertz Time-Domain Data

Terahertz time‐domain spectroscopy is a well‐established technique to study the far‐infra‐ red electromagnetic response of materials. Measurements are broadband, fast, and per‐ formed at room temperature. Moreover, compact systems are nowadays commercially available, which can be operated by nonspecialist staff. Thanks to the determination of the amplitude and phase of the recorded signals, both refractive index and absorption coefficient of the sample material can be obtained. However, determining these electro‐ magnetic parameters should be performed cautiously when samples are more or less transparent. In this chapter, we explain how to extract the material parameters from terahertz time‐domain data. We list the main sources of error, and their contribution to uncertainties. We give rules to select the most adapted technique for an optimized characterization, depending on the transparency of the samples, and address the case of samples with strong absorption peaks or exhibiting scattering.

Emitting and Receiving Terahertz Vectorial Antennas Based on Cubic Electro-Optic Crystals

Based on optical rectification in a ZnTe crystal, a vectorial terahertz (THz) emitter is here theoretically and experimentally demonstrated. The use of the particular orientation 〈111〉 leads to a polarization state angle tunable THz source. This configuration requires only an optical wave plate to manage the impinging optical polarization state, thus adjusting the transverse THz electric field orientation. Moreover, the optical rectification efficiency as well as the THz signal bandwidth remain constant from horizontal to vertical Terahertz polarization. The same crystal, acting then like a THz receiver, allows to perform the vectorial analysis of a THz pulse.