Patent ID: 8306372

Claim:
A waveguide-type polarizer comprising: a Z-cut lithium niobate substrate; an optical waveguide that has a ridge structure and is formed on the substrate; characterized in that a low refractive index film is formed with a thickness satisfying 0≦n·t/λ≦0.3742 (where n is a refractive index, t is the thickness of the film, λ is the wavelength of a light wave, and the unit of the thickness and the wavelength is μm) on the side of the ridge structure; and a high refractive index film is formed with a thickness satisfying 0.089≦n·t/λ on the low refractive index film, wherein the width of the ridge structure is a ridge width where the distribution of ordinary light of the light waves propagated through the optical waveguide changes and the distribution of the extraordinary light of the light waves does not change, the angle of the ridge structure is less than 90°, and the waveguide-type polarizer has a function of transmitting extraordinary light.