Electro-optic and Magneto-optic Nonintrusive Field Sensing Technologies

Correct visualization of electromagnetic waves requires a sensor capable of detecting the actual EM field non-intrusively. This chapter introduces electric and magnetic field sensing technologies that utilize nonintrusive E-field and B-field probes based on the Pockels electro-optic (EO) effect and the magneto-optic (MO) Faraday effect. In contrast to conventional field sensors, such as antennas and diode sensors, which contain metallic components, these field probes are made of entirely dielectric materials. Hence, they negligibly perturb the electric and magnetic fields that they measure. The detected electric and magnetic fields are “true” and nearly distortion-free, and the waveform of the field is exact even in a complex electromagnetic environment, where conventional field sensors fail to produce reliable and reproducible results. The EO and MO field sensors have an extreme frequency bandwidth. This extensive bandwidth enables the EO and MO probes to detect all Fourier frequency components for a complex waveform. Hence, in principle, the sensors can measure the exact waveform for the EO probe, from ELF up to terahertz frequency. They are compact and also have an exceptional dynamic range. In addition, the sensors cause negligible reflection and perturbation of the electromagnetic field, enabling them to detect the near-field and far-field without disturbing the signal source – the capability a conventional probe cannot provide. Also, they are vector sensors capable of detecting the direction of the E- and B-fields. So, the field probes are suitable for various applications, which are otherwise impossible or very difficult to perform with conventional field probes.