Optical bias angle control method for electric field sensor using Mach-Zehnder interferometer

Abstract

An electric field sensor using a Mach‐Zehnder interferometer can be made compact, used for wide‐band applications, and does not disturb the surrounding electromagnetic field. Because of these merits, its application to EMC measurement is promising. However, because it is not clear how to adjust the operating point (optical bias angle) of the optical modulator used for the electric field sensor, its dynamic range is limited. This paper proposes a method to adjust the operating point by applying force to a point on the optical crystal substrate used for the optical modulator. First, the relationship between the applied force and optical bias angle is theoretically analyzed, taking into account the change in waveguide length and change in the refractive index when load is applied. Then, it is shown that the change in the waveguide length is more dominating than the change in the refractive index. An electric field sensor was actually fabricated to show that the optical bias angle can be adjusted as theoretically predicted and that its temperature dependence is comparable to that of a conventional electric field sensor. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(8): 53‐61, 2000