OPTICAL WAVEGUIDE TYPE POLARIZER

PURPOSE: To control the extinction rate for polarized light and optical loss by forming a dielectric film between the surface of an optical waveguide and a metal in such a manner that the dielectric film has a lower refractive index than the core of the optical waveguide. CONSTITUTION: A core 52 to be used as an optical waveguide 1 is formed in the upper part of an optical waveguide element 51 in such a manner that the upper face of the core 52 is exposed to form one face with the upper face of the optical waveguide element 51. A dielectric film 3 is formed on the upper face of the core 52, namely on the surface of the optical waveguide 1, in such a manner that the film 3 crosses the element 51 at one position in the longitudinal direction of the optical waveguide 1. The film 3 is a SiO2 film having a lower refractive index than the optical waveguide 1. When light transmits through the part of the waveguide 1 where a metal 2 is present on the film 3, the electromagnetic component permeating the metal 2 changes with the film thickness of the film 3. Therefore, by changing the film thickness of the dielectric film 3, the optical loss in the lateral polarized light and longitudinal polarized light can be controlled. Also, by changing the film thickness of the film 3, the extinction rate of polarized light can be controlled.