High Electric Field Measurements Research Articles

Packaging method and temperature characteristics of miniature e-field probe with fiber-lInBo 3 evanescent coupler

The fiber-waveguide evanescent coupler (FWEC) is one of the most promising directions in optical fiber sensors for electric field measurement. FWEC has extraordinary measurement performance, including millimeter-level size, high spatial resolution, broad upper limit, and free of discrete optical elements. Therefore, it has a wide range of applications, especially for very fast transient overvoltage and high electric field measurement. However, like all kinds of optical electric field sensors, the output of FWEC also shifts with temperature. Besides, the mechanical stability of FWEC is weakened as most of the cladding of D-type single-mode fiber (D-SMF) has been removed. In this paper, the FWEC sensor with stable transmission spectra is fabricated by monitoring the real-time coupling state of D-SMF and Z-cut LiNbO3. A uniform package coating of about 150 μm is formed by precisely controlling the injected QLE 1101 silicon gel. The stability test shows that the spectral distortion of packaged FWEC is only about 1.7%, indicating that the impact of packaging on the measurement performance is negligible. Through theoretical analysis and experimental verification, the peak wavelength of FWEC shifts linearly with temperature with a sensitivity of 0.08 nm/˚C. Therefore, the peak wavelength shift can be selected as the characteristic index to correct the measurement result in practical application.

Preparation of quaternary boro-phosphate multifunctional glasses and their structural, optical, switching and antibacterial properties

In this paper, the glass composition of (50-x)P2O5-xB2O3-30CuO-20Li2O (x = 0, 5, 10, 15, and 20 mol%) was prepared and the effect of P2O5 substitution by B2O3 on their structural, optical, switching, and antibacterial characteristics was studied. FT-IR spectra showed that an increase in the B2O3 content leads to gradual erosion of the phosphate characteristic bonds, and the emergence of borate-related ones by creating new linkages between phosphate chains through P–O–B bonds and formation of highly cross-linked P3-O-B4 linkages. The incorporation of boron up to 20 mol%, also leads to an overall increase in glass transition temperature together with a decrease in the molar volume which both, implied improvement of glass stability. Optical studies revealed that all glasses are almost transparent in the UV–Vis region with high band gap energy about 3.83 eV, which experiences a red-shift with increase in the B2O3 concentration to 15 mol%. By calculating the wavelength-dependent optical parameters, however, it was found that the present glass composition with highest concentration of B2O3 shows refractive index near one and very negligible extinction coefficient (and imaginary optical dielectric function) at the visible region. These results support the great potential of the mentioned glass composition as a window layer. The analysis of the high electric field measurements demonstrated a wide range reduction in switching threshold voltage as the B2O3 content increases. This hints at their potential application as electrical-induced sensors. The antibacterial activity of x = 0 and x = 5 glass compositions has been examined by zone of inhibition measurements and it was found that they have potential applications as antibacterial agent.

High electric field measurement using slab-coupled optical sensors.

A fiber-optic electric field sensor was developed to measure electric field up to 18MV/m. The sensor uses resonant coupling between an optical fiber and a nonlinear electro-optical crystal. The sensing system uses high dielectric strength materials to eliminate dielectric breakdown. A postprocessing nonlinear calibration method is developed that maps voltage change to wavelength shift and then converts the wavelength shift to electric field using the transmission spectrum. The nonlinear calibration method is compared against the linear method with electric field pulses having magnitudes from 1.5 to 18MV/m.

Design and application of an integrated electro-optic sensor for intensive electric field measurement

Impulse electric field measurement should satisfy some special requirements such as intensive signal amplitude, appropriate insulation, broadband response, and small size. Three types of integrated electro-optic sensors, designed and fabricated for measuring intensive impulse electric field, was implemented in this paper. The theoretical concerns and specific characteristics of these integrated electro-optic sensors were illustrated in terms of their structures and key parameters. The time domain input/output characteristic and frequency response of the sensors were examined too. Comparison of the time domain characteristics of these sensors revealed that the mono-shield sensor was more efficient than those with antennas in measurable amplitudes, which is critical for high electric field measurement in gas breakdown research. In addition, the application of the sensor in the lightning impulse experiment upon air gap not only verify the existence of streamer charge but also ensured that this sensor is expected to be widely used in transient measurement investigations such as the measurement of lightning electric field, air breakdown procedure, and maybe surface discharge.

A comparative study of electrical and optical properties of InN and In0.48Ga0.52N

We present results of our studies concerning electrical and optical properties of In0.48Ga0.52N and InN. Hall measurement were carried out at temperatures between T=77 and 300K. Photoluminescence (PL) spectrum in InN and In0.48Ga0.52N. InN has a single peak at 0.77eV at 300K. However, the PL in In0.48Ga0.52N has two peaks; a prominent peak at 1.16eV and a smaller peak at 1.55eV. These two peaks are attributed to Indium segregation corresponding to a high Indium concentration of 48% and a low concentration of 36%. High electric field measurements indicate that drift velocity that tends to saturate at around Vd=1.0×107cm/s at 77K in InN at an electric field of F=12kV/cm. However, in In0.48Ga0.52N the I–V curve is almost linear up to an electric field of F=45kV/cm, where the drift velocity is Vd=1.39×106cm/s. At applied electric fields above this value a S-type negative differential resistance (NDR) is observed leading to an instability in the current and to the irreversible destruction of the sample.

High electric field measurement and ice detection using a safe probe near power installations

The present study concerns an optical device measuring electric field by using a lithium niobate (LiNbO 3) crystal as the sensing medium, without any electrodes. Such a device has the advantage of providing a good galvanic insulation of materials and persons. A likely application is the high electric field measurement near electric power installations (frequency 50–60 Hz). The principle of measurement implements the electro-optic effect in the crystal. The sensing medium has been designed—thanks to finite element simulations—and a probe prototype constructed, with which measurements can be made far away through optical fibers. Experimental setups are developed in order to validate the physical principle, and also to calibrate the probe. As simulation results are in good agreement with experimental results, the behavior of the probe in a real environment is presented. Finally, the use of the probe to detect ice accretion on high power electric cables is proposed and validated.

High electric field measurement of dielectric constant andlosses of ferroelectric ceramics

Nonlinear behaviour of power piezoceramic materials has to be studiedunder strong electric fields. A bridge designed for measuring it at lowfrequency is described. It consists basically of a capacitancecomparison bridge that can be used in two different modes: balanced andunbalanced. The nonlinear electric displacement is split intodissipative and nondissipative terms. Dielectric constant is computedfrom the last term and related to the instantaneous field. The behaviourof soft and hard PZT ceramic materials has been tested according to thismodel. In both materials, the dielectric constant not only depends onthe instantaneous value of the field but also on its amplitude. Whilethe dependence of the real and imaginary parts of the dielectricconstant in soft ceramics is large and practically linear to the fieldamplitude, in hard PZT it is low and nearly quadratic. The rate betweenboth parts depends on the type of ceramic. Dielectric constant can bedivided into two terms. One term is allied to the irreversible motion ofdomain walls, while the other is related to reversible motion. Balancedand unbalanced modes have been tested for both materials, and resultsare coherent. Accuracy and limitations of the method are discussed.

Sliding motion of charge density wave in quasi-two-dimensional η-Mo 4O 11 crystal

High electric field measurements of electrical conductivity of the CDW material of quasi-two-dimensional η-Mo 4O 11 (transition temperatures T c1 = 105 and T c2 = 35 K) have been made. Here we show the existence of a sliding motion of depinned CDW condensate above a threshold field E t (= 20−30mV cm −1) in the first CDW state ( T c2 < T < T c1 ) and a delayed response of the conductivity in the second CDW state ( T < T c2 ).

High electric field effects in amorphous semiconducting (As 2S 3) 1− x(PbS) x

High electric field measurements on (As 2S 3) 1− x (PbS) x amorphous semiconductors have been made in sandwich geometry at 50 and 80°C. They reveal the non-linear effects associated with conduction in amorphous semiconductors. The x = 0.1 composition exhibits an anomalous increase in current at an applied field of about 22.5 KV/cm which is found to be independent of the temperature.