| 摘要 |
PROBLEM TO BE SOLVED: To obtain a grating element without polarization dependence.SOLUTION: A grating element includes an optical waveguide 12 constituted of a clad 14 provided on the side of a principal surface 8a of a substrate 8, and a core 16 provided in the clad and for converting light with a wavelength λ corresponding to a period λ of regular irregularities C formed in the core into a polarized wave and reflecting it. The clad includes a first clad 14a and a second clad 14b having a refractive index smaller than that of the first clad, provided on the principal surface in this order. The core is provided between the first and second clads, and a material forming the core has a refractive index larger by 40% or more than that of a material forming the first clad. The irregularities are provided on the side surfaces of the core. A formula of Λ=λ/(nTE+nTM) is satisfied, where nTE represents an equivalent refractive index of a TE wave with a wave length λ and nTM represents an equivalent refractive index of a TM wave with a wave length λ. |
