An optical waveguide device is provided that can reduce external
interference noise. The optical waveguide device includes a substrate, an
optical waveguide formed on the substrate, a periodic polarization
inversion region formed on the optical waveguide, and an optical thin film
formed in a portion of the optical waveguide. The optical waveguide
(refractive index: N2) and the optical thin film (refractive index: N1)
differ in refractive index dispersion, and the magnitude relationship
between the refractive indexes is reversed depending on wavelength. The
relationship N1>N2 is established for light having a shorter
wavelength, while the relationship N2>N1 is established for light
having a longer wavelength.
