Waveguide-type polarizer
The waveguide-type polarizer includes: a Z-cut lithium niobate substrate; an optical waveguide having a ridge structure and formed on the substrate; a low refractive index film formed with a thickness satisfying 0≦n·t/λ≦0.3742 (where n is a refractive index, t (μm) is the thickness of the film, and λ (μm) is the wavelength of a light wave) on the side of the ridge structure; and a high refractive index film formed with a thickness satisfying 0.089≦n·/λ on the low refractive index film. 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 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.
1. 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.
2. The waveguide-type polarizer according to claim 1 ,
wherein the thickness of the low refractive index film satisfies the following condition:
0.0935 ≦n·t /λ≦0.3742.
3. The waveguide-type polarizer according to claim 1 ,
wherein a main component of the low refractive index film is SiO 2 , and
impurities are mixed with the SiO 2 film to control the refractive index of the film.
4. The waveguide-type polarizer according to claim 2 ,
wherein a main component of the low refractive index film is SiO 2 , and
impurities are mixed with the SiO 2 film to control the refractive index of the film.