JPS6420523A - Optical isolator - Google Patents

Abstract

PURPOSE:To realize the separation/synthesis of P-polarization and S-polarization, by using an isolator unit in which a PBS prism having structure adhering a parallel plate on the inclined plane of a rectangular prism via a polarizing film consisting of a dielectric multilayer, etc., is used. CONSTITUTION:In a forward direction, a beam of light from a lens 32 is separated to an S wave and a P wave at the polarizing film 44 of the PBS prism 12, and the S wave is reflected and the P wave transmits the polarizing film, and is reflected on the end face 46 of the parallel plate, then, advance to a Faraday rotor 14, and is rotated at 45 deg. in a clockwise direction based on the impressing direction of a magnetic field H, and furthermore, it is rotated by 45 deg. in the same direction at a 1/2-wave plate 16. Thereby, the P wave and the S wave are inputted to the PBS prism 18 after the P wave is changed to the S wave and the S wave to the P wave, and are reflected on the polarizing film 44 and the end face 46 of the parallel plate, and they are condensed and advance to a 90 deg. rotary polarizing plate 30 after being changed to circularly polarized light, then, inputted to the PBS prism 22. The same operation as that of the isolator unit at a first stage is performed again, and the beam of light is separated to the P wave and the S wave, and the polarizing plane is rotated at 90 deg. in total, rotation at 45 deg. in a rotor 24 and a 1/2-wave plate 26, respectively, then, the P wave is changed to the S wave and the S wave to the P wave, and are condensed by a prism 28 again, then, emitted to a lens 34 after being changed to the circularly polarized light.