Technologies – Electro-Optic & Magneto-Optic Detection
In certain types of crystals, the application of an electric field causes a change in the refractive-index tensor of the medium. This phenomenon is known as the electro-optic (EO) effect or Pockels effect, and those crystals are referred as electro-optic crystals. This effect makes it possible to detect the presence of an electric field in the crystal. Optical radiation (typically, a laser beam) travels through the crystal that has a modulated index of refraction (due to an applied electric field), and it exhibits a different state of polarization as compared to laser light 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 electric field.
The magneto-optic (MO) effect, arising from the Faraday Effect, is quite similar to the EO response above. However, unlike the EO effect, the output light beam in MO modulation has its linear polarization preserved, with only the angle of polarization being rotated. Like the EO effect, the strength of MO modulation is determined by factors such as the MO coefficient (most commonly referred to as the Verdet constant), the incident magnetic-field strength, the interaction length, and the beam wavelength. The fundamental physics behind both the EO and MO effects is distortion of electrons in the crystalline structures of the EO and MO media, an extremely fast phenomenon that makes extremely broadband field detection possible.
Advanced Fiber Sensors, Inc., founded by pioneers in practical implementations of EO and MO phenomena, has developed, and introduced the fiber-coupled EO and MO sensors for broad range of test & measurement applications where detailed knowledge of electric and magnetic fields is critical.