POLARIZATION PLANE CONTROLLER FOR DELAYED SELF-HETERODYNE DETECTION

摘要

PURPOSE:To obtain a small-sized and inexpensive polarization plane controller for heterodyne detection by using a 1st polarizing means having a Fabry-Perot resonator and quarter lambda plate in the rear stage in place of a Faraday element and using electrooptic elements for both the 1st and 2nd polarizing means. CONSTITUTION:Light 1 to be measured is bisected by an optical branching filter 21. One of the light is subjected to a frequency shift by an acoustooptic modulator 3 and is entered to the 1st polarizing means 60a. This light is circularly polarized by the electrooptic elements 24a, b of the means 60a and is linearly polarized by the quarter lambda plate 27 through the Fabry-Perot resonator 23. This polarized light enters a polarized beam splitter 28. The voltage on the elements 24a, 24b of the splitter 28 is so controlled as to allow transmission of the more P wave. The other light is entered through a delay fiber 22 to the 2nd polarizing means 60b and the polarization plane is controlled to the linearly polarized light in the same manner as in the means 60a. The P wave transmits the splitter 28, is circularly polarized by the quarter lambdaplate 27, is reflected by the resonator 23 and is again linearly polarized by the plate 27. The S wave is reflected by the splitter 28 and is joined to the primary light from the modulator 3 to constitute the interference light which enters a photoelectric converter 31a.