Electric field sensors

This chapter provides an overview of the basic principles and designs of such sensors. A chemical sensor to detect trace explosives and a broadband fiber optic electric-field sensor are presented as practical examples. The polymers used for the trace explosive sensor are unpoled and have chromophores randomly orientated in the polymer hosts. The electric field sensor uses a poled polymer with chromophores preferentially aligned through electrical poling, and the microring resonator is directly coupled to the core of optical fiber. 

For an RF electric field sensor, bandwidth (speed) is another important requirement. The speed of a resonator is determined by the cavity ring down time r = QX/c. As in any devices using resonating structures, a trade off between sensitivity (which increases with Q) and speed (which decreases when Q increases) has to be made. At the wavelength of 1.55 pm, Q factors of 104 and 106 translates to a sensor bandwidths of 20 GHz and 200 MHz, respectively. 

All-Dielectric Radio Frequency Electric Field Sensor... 

Fig. 2.16 (a) A schematic drawing of polymer microring resonator couple to a side polished optical fiber, (b) A microscope image of the fabricated EO polymer electric field sensor, (c) SEM image of resonators fabricated on the polished flat of a free standing fiber. The scale bar in the picture represents 100 pm. Reprinted from Ref. 15 with permission. 2008 Institute of Electrical and Electronics Engineers... 

Fig. 2.17 The output of the RF electric field sensor at 550 MHz and 10 dBm RF input. Reprinted from Ref. 15 with permission. 2008 Institute of Electrical and Electronics Engineers...

Different concentrations of BG bacterial spores (103 107 spores per mL) were introduced into the electric field sensor chip-based flow cell and an appropriate... 

The high EO activity and solvent resistance allowed these materials to be processed through multiple lithographic and etching steps to fabricate a race-track-shaped microring resonator. By coupling this resonator with a side-polished optical fiber, a broadband electric-field sensor with a high sensitivity of 100 mV/m at 55 MHz has been demonstrated [116]. 

Fig. 9.6.1 Cross sectional view of a fringing electric field sensor (see text for details). Different connection schemes can be used to vary the penetration depth of the sensor.

A. V. Mamishev, Design principles for multi-channel fringing electric field sensors, IEEE Sens. J., Apr. 2006, 6(2), 434-440. 

An electrode pair is a sensor measuring the potential difference between two electrodes. Knowing the distance between them the sensor is also an electric field sensor. 

An electric field sensor or a magnetic field sensor prepared for each circuit will detect all opens and shorts in branched circuits. Another big advantage of the non-contact test system is that it works for general circuits that have a common bus bar for electrical plating. The circuits must be isolated to conduct the electrical short test when traditional contact test methods are being used. 

Other devices that can be fabricated with NLO polymers are for example sensors for electric field. A number of sensors fabricated with EO polymers to detect electric field signals and map the electric field distribution have been implemented in the last years based on Mach-Zehnder intensity and polarization modulators. Other sensors are based on asymmetric Fabry-Perot microcavities to convert phase modulation into amplitude modulation and enhance the samphng signals. Very recently Sun et al. [172] presented a novel broadband electrooptic electric field sensor fabricated with an EO polymer microring resonator coupled to the core of a side-polished optical fiber. A sensitivity of 100 mV/m has been achieved at frequencies up to 550 MHz. 

M. D. Mennclstein. Optical-fiber oopolynKr-film electric field sensor. AppL Opt. 22 1006 (1983). 

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