OPTICAL WAVEGUIDE TYPE DIFFRACTION GRATING AND METHOD FOR MANUFACTURING THE SAME

摘要

The method of making a diffraction grating device in accordance with the present invention comprises the steps of preparing an optical waveguide having an optical waveguide region doped with an additive adapted to generate a refractive index change upon irradiation with refractive index change inducing light having a predetermined wavelength, and a phase grating having a predetermined projection and depression pattern; separating the optical waveguide and the phase grating from each other by a distance yielding a predetermined optical path difference between zero-order transmitted light and second-order diffracted light of the refractive index change inducing light such that a modulation intensity of interference light between the zero-order transmitted light and second-order diffracted light becomes 85% or less of that obtained when no optical path difference exists between the zero-order transmitted light and second-order diffracted light; and making the refractive index change inducing light incident on the phase grating, so as to form an interference fringe of first-order diffracted light in the optical waveguide region of the optical waveguide, thereby forming the optical waveguide region with a diffraction grating. The present invention provides a method of making a diffraction grating device which is easy to make while exhibiting a sufficiently small cutoff amount in the wavelength band of 0.9 lambda B to 0.95 lambda B (where lambda B is a cutoff peak wavelength) originally meant to be transmitted. <IMAGE>