Electro-optic Probe Research Articles

Photonic-assisted diagnosis of electromagnetic coupling into a generic object

A photonic-assisted probing system to diagnose the electromagnetic influences of an electronic subsystem against intense electronic threat is presented. The shielding effectiveness of a generic missile and the coupled fields into the missile cavity were investigated by a fiber-coupled electro-optic field probe with its associated photonic system. To characterize the absolute field strength in the cavity, the probe was calibrated with a standard gain horn antenna at the R band by generating known fields toward the generic object. The fields coupled into the metallic cavity can be resonantly built up at multiple frequencies over a power range of 32 dB. The measured resonance characteristics of the hollow generic cavity showed good agreement with the computational data. This indicates that the electromagnetic susceptibility of an electronic sub-system with an enclosed metallic cavity can be readily exploited using the photonic-assisted system presented here. The strength and spectra of the resonant fields that passed through the aperture of the generic cavity at various internal locations are presented. This measurement system is quite effective at measuring actual fields without the need for a probe compensation procedure. Thus, it can be utilized for diagnosing the shielding of a generic system against intentional electromagnetic threats when the interiors of the generic objects become highly sophisticated.

Fiber-mounted Electro-optic Probe for Microwave Electric-field Measurement in Plasma Environment

Fiber-mounted Electro-optic Probe for Microwave Electric-field Measurement in Plasma Environment

Sensitivity enhancement of electro-optic polymer probing system using photo-isomerization and Fabry-Pérot effects

A sensitivity enhancement method for an external electro-optic (EO) probing system using a poled polymer as an EO sensor is proposed. A pumping laser, which induces the photo-isomerization effect in a prepoled EO polymer, and a tunable probing laser, which induces Fabry-Pérot effect, are combined to enhance the polymer EO sensor sensitivity. Results of an experiment with an EO sensor made of Disperse Red 1 poly(methy1 methacrylate) that demonstrates this combined effect are reported.

Electro-optical probe for studying local fields in organic heterostructures

Dielectric, optical, and electro-optical properties of thin Langmuir films (40–130 nm thick) of meso-substituted palladium tetraphenylporphyrin have been investigated. The key parameter of the characteristic electro-absorption band of this material—the difference in the polarizability for the excited and ground states of its molecules—has been determined. The example of determining the local field in the polymer ferroelectric in the composition of two-layer heterostructure is shown.

New method for in live-line detection of small defects in composite insulator based on electro-optic E-field sensor

Preliminary results based on experimental tests in laboratory and numerical investigation concerning the live-line detection of a conductive defect in HV composite insulator are depicted. The proposed method is based on E-field sensing using a non-invasive and compact pigtailed electro-optic (EO) single-ended probe. Measurements and numerical FEM modeling were done on a clean dead-end 28 kV composite insulator on which conductive defects of different size and position were simulated. Based on these simulations, the optimal location and orientation of the EO probe were determined regarding the conductive defect length and position. Laboratory tests were performed to validate these results and demonstrate the efficiency of the new detection method. The experimental results have demonstrated that using the optimal EO probe orientation, the E-field sensor was able to detect and locate conductive defect as short as 15 mm × 1 mm in contact with the HV electrode and of 26 mm × 2 mm between sheds. Moreover, the experimental tests have demonstrated the ability of the EO sensor to detect the presence of corona discharges induced by the conductive defects.

Electro-optic sensor for specific absorption rate measurements

We propose a sensor system to measure the specific absorption rate at radio frequencies, using a matrix of electro-optic (EO) sensors. The aim is to replace the conventional metallic antenna scanned by a robot inside an open phantom with a matrix of small probes positioned inside a closed phantom. Results are presented for a dual sensor, showing the feasibility of the proposed approach. The two EO probes interrogated by the same laser are shown to detect electric fields smaller than 1 V/m. Measurements are conducted both with the probes in air and inside the phantom liquid.

Electric field measurement in microwave discharge ion thruster with electro-optic probe

In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters.

Confinement of THz surface waves on the subwavelength size metal waveguide

We investigate surface plasmon waves propagating on planar Goubau lines, so-called Goubau modes, using a guided-wave terahertz spectroscopy system based on a freely positionable electrooptic probe. We show the radial nature of the Goubau mode and its confinement around the Goubau line over a few tenths of microns (λ/10).

In situ characterization of pin diode waveforms using electro‐optic sampling

AbstractIn situ measurements of nonlinear waveforms produced by a PIN diode under large‐signal excitation have been performed using ultrafast electro‐optic (EO) sampling.The waveforms were sampled using an EO probe positioned immediately after the diode. These data validate a nonlinear model and improve representation of the waveform across the circuit. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2653–2656, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27119

Electrooptic Probe Adapted for Bioelectromagnetic Experimental Investigations

In this paper, we present radio-frequency electro-magnetic field characterization of an electrooptic (EO) probe. This probe is able to simultaneously measure temperature and one component of the electric field (e-field) in a continuous wave (CW) or in a pulsed regime. For this purpose, linearity, selectivity, and sensitivity measurements are performed in air and in a cuvette filled with a water solution. The media are exposed to 1800-MHz CW electromagnetic wave through a transverse electromagnetic cell. Numerical characterization is also performed using finite-difference time-domain simulations. The EO probe presents a dynamic range exceeding 70 dB. Selectivity up to 25 dB is measured, demonstrating the ability of the EO probe to measure one unique component of the e-field. The EO probe sensitivity is equal to 0.77 and to 0.18 V · m-1Hz-½, in the air and in the water solution, respectively. This millimeter-sized EO probe is particularly suited for the measurement of ultrawide bandwidth and high-voltage e-fields up to a few megavolts per meter.

Simultaneous High Intensity Ultrashort Pulsed Electric Field and Temperature Measurements Using a Unique Electro-Optic Probe

High intensity nanosecond pulsed electric fields and temperature were simultaneously measured using a unique electro-optic (EO) probe. The measurements were performed in an electroporation cuvette with 4 mm electrode gap and filled with a buffered salt solution. High voltage generators delivering 2.6 and 10 ns duration pulses with different pulses shape and intensity were investigated. The EO probe linearity was characterized up to 2 MV/m. The temperature measurement uncertainty was found to be less than 22 mK. Excellent measurement abilities were achieved with this EO probe showing its suitability for bioelectromagnetic experiments and particularly for wideband high intensity field applications.

IMPROVEMENT OF ELECTRICAL NEAR-FIELD MEASUREMENTS WITH AN ELECTRO-OPTIC TEST BENCH

In this paper, two difierent kinds of near-fleld measure- ment techniques are presented. The flrst one uses coaxial probes that do not give precise measurements on microelectronic devices. We saw in (1) that the spatial resolution of these probes reaches 500m for monopole and is millimetric for dipole probe. The second one is based on the Pockels efiect that converts an electromagnetic (EM) fleld into optical modulation. Our objective is to improve the Ex=Ey near-fleld measurement with this second technique. The performance of the electro-optic (EO) probe is compared with dipole probes of 2.5 and 5mm with the use of simulations and measurements, on a wire above a ground plane and on coupled microstrip lines. At the end, a discus- sion about the technical limitations of the EO probe is made.

Specific Absorption Rate Assessment Using Simultaneous Electric Field and Temperature Measurements

In this letter, the temperature measurement ability of an electrooptic probe as well as specific absorption rate (SAR) assessments via simultaneous in situ temperature and electric field characterization are reported. The measurements are carried out at 1800 MHz in a Petri dish filled with a water solution and placed in a transverse electromagnetic (TEM) cell. From the temperature sensitivity measurements, a standard deviation of 27 mK is obtained. The SAR values obtained both via temperature and electric field are also compared to finite-difference time-domain (FDTD) simulated numerical results. A difference of 5% is obtained between the two experimental SAR values. These measured SAR values are consistent with those obtained by the numerical simulations.

Optically enhanced sensitivity of external electro-optic polymer probing system

We propose an optical-sensitivity-enhanced external electro-optic (EO) measurement system using a poled polymer as an EO sensor. A pumping laser is used to induce the photoisomerization effect in a prepoled EO polymer to both enhance and maintain the noncentrosymmetric molecular orientation. This approach increases the EO coefficient and, hence, enhances the EO measurement sensitivity. Experimental results of an EO sensor made of DR1/PMMA show that this method can improve the sensitivity by at least a factor of 2.

Two electric-field components measurement using a 2-port pigtailed electro-optic sensor

Based on an isotropic electro-optic crystal, a two-port pigtailed electro-optic sensor has been built. The probe allows to measure two orthogonal components of the ambient electric field. The sensor intrinsically presents a temperature-dependent free response. The two measured electric field components are orthogonal to the sensor revolution axis, leading to a transverse electro-optic probe. Magnitude and orientation of the electric field are measured simultaneously with an accuracy of 0.5 dB and 2°, respectively. The rejection of orthogonal components to the electric field vector reaches 30 dB.

Note: Simultaneous electrical and optical detection of expanding dense partially ionized vapour clouds

The scheme and construction of an electro-optical probe able to collect charge and detect optical emission from expanding dense partially ionized vapour clouds are reported. The instrument can be applied to phenomena such as dust impact ionization and solid target laser ablation. First, results of measurements of expanding plasma cloud formed upon ablating W target are presented. Use of the instrument in different experimental facilities, including tokamak, is discussed.

Calibrated 100-dB-dynamic-range electro-optic probe for high-power microwave applications

Highly stable electro-optic field probe with wide dynamic range is presented. The highly efficient electro-optic modulation mechanism--based on interference and field-induced phase retardations using a new embodiment with a relatively thick sensor crystal mounted on a fiber--is explained. The probe is calibrated up to 3.5 GHz through the use of a micro-TEM cell and a standard gain horn antenna, both devices in which the electric field may be calculated at the specific sensing location of an electro-optic probe. The field-calibrated sensor shows over 100 dB (≤ 1 V/m to > 100 kV/m) of linear dynamic range. Also, an issue with the instability of the sensors that often occurs in intense electric-field measurements associated with electro-optic crystals is overcome by a real-time, bias-control loop. The stabilized sensor performance and its potential use for (pulsed) high-power-microwave applications are discussed.

Ultrahigh sensitivity electric field detection with a liquid electro-optical film

In this Letter, an electro-optical probe configuration with polar molecule liquids as the sensing film is proposed to improve the voltage sensitivity. This method exhibited increases in intrinsic sensitivities better than 0.1 mV/√Hz, 2 orders of magnitude larger than the normal method using a GaAs probe in the same measurement system. Based on the mechanism of orientation polarization, the electro-optic coefficient was measured to be 250 pm/V by the Teng-Man method at a modulation field of 100 Hz. This technology will be promising in applications of low-frequency field detection.

Recent Advances in the Design of Electro-Optic Sensors for Minimally Destructive Microwave Field Probing

In this paper we review recent design methodologies for fully dielectric electro-optic sensors that have applications in non-destructive evaluation (NDE) of devices and materials that radiate, guide, or otherwise may be impacted by microwave fields. In many practical NDE situations, fiber-coupled-sensor configurations are preferred due to their advantages over free-space bulk sensors in terms of optical alignment, spatial resolution, and especially, a low degree of field invasiveness. We propose and review five distinct types of fiber-coupled electro-optic sensor probes. The design guidelines for each probe type and their performances in absolute electric-field measurements are compared and summarized.

A multi-layer electro-optic field probe

We present a novel design method and sensing scheme for an electro-optic field probe using multi-stratified layers of electro-optic wafers. A serial stack of cascaded layers is found to be capable of enhancing the performance of interferometric electro-optic light modulation that utilizes the slopes of interference fringe patterns and field-induced electro-optic phase retardations within wafers. The absolute sensitivity of the probe is also characterized with a micro-TEM cell that generates electric fields distributions with accurate, calculable strength for use in probe calibration. The sensitivity of a multi-layered probe-per unit electro-optic wafer volume--was enhanced by 6 dB compared to that of a single-layer one.