In noncentrosymmetric crystals, the application of an RF electric field directed along certain crystal axes causes a change in the indices of refraction encountered by an incident optical beam. This phenomenon is known as the electro-optic (EO) effect or Pockels effect, and those crystals are referred to as electro-optic crystals. The electro-optic effect affords a widely used means of controlling the phase or intensity of the optical radiation. In another sense, this effect also makes it possible to detect the presence of an RF electric field impinging on the crystal. Optical radiation (typically, a laser beam) travels through the crystal that possesses the RF-modulated index of refraction, and the laser beam exhibits an altered state of polarization with respect to the beam that travels through the crystal without an applied electric field. This comparison of polarization states allows determination of the amplitude and phase of the existing RF electric field. Since the electro-optic sensing phenomenon relies on small displacements of the atomic crystal structure, the response time of the process is extremely short. This short response time makes it possible to measure high-frequency electric fields up to the Terahertz regime. Because the electro-optic field-sensing technique is based on the optical modulation of the incident laser beam, its spatial resolution is determined by the size of the focused laser beam within a probe. This can be easily reduced to less than 10 µm. Due to its broad measurement bandwidth and high spatial resolution, the EO near-field measurement technique is a promising means of characterization for RF systems such as micro/millimeter-wave integrated circuits or radiating structures, including large-scale active arrays. In particular, the EO near-field imaging method features non-contact and non-destructive evaluation of RF electronics. In addition, conventional electrical measurement techniques require some type of metal structure for the resonant detection of an RF signal. However, the electro-optic field-imaging method requires neither a metal pattern near the signal sensor area, nor metallic interconnects between the probe and a read-out instrument. As a result, the undesirable effects caused by introducing metal within the vicinity of a device under test (DUT), such as distortion of the signal and disturbance in the operation of the DUT, are significantly reduced.

OPTEOS, Inc proudly introduces the most advanced electric-field-imaging system available to the microwave market, using micromachined GaAs electro-optic probe tips that are optically interrogated using a fiber-optic tether. This fiber-based system exhibits a lower permittivity than other scanning field probes, provides excellent measurement flexibility so that the scanning can be performed at any arbitrary orientation, and allows insertion of the field sensor into microwave enclosures. In the extreme limit, the fiber-based EO field-mapping system makes it possible to extract electric-field distributions of complicated micro- and millimeter wave circuits that are shielded by metal packages. The fiber-based EO system can be applied to, among other activities, internal-node circuit diagnostics (e.g., for power amplifiers), ultra-high-resolution, near-field antenna/array characterization, phased-array calibration and monitoring, localization of electromagnetic emissions, design of prototypes, and analysis of faults and failures.