PROBLEM TO BE SOLVED: To provide a phase grating mask with which a plurality of diffraction gratings whose period is different from one another can be easily formed on an optical waveguide, a method for forming the diffraction grating utilizing the phase grating mask, a diffraction grating element manufactured by utilizing the method, etc.;SOLUTION: First, the phase grating mask 10 composed of a transparent flat plate 11 on one surface 11a of which a plurality of phase gratings 12a-12h whose period is different from one another are arranged side by side, and a plurality of optical waveguides 22a-22h arranged in parallel are prepared. Next, the phase grating mask is arranged in such a manner that the surface on which the plurality of phase gratings are arranged side by side is confronted with the plurality of optical waveguides. The diffraction grating element 20 is manufactured by irradiating the plurality of optical waveguides with refractive index variation inducing light 30 having the wavelength which induces refractive index variation through the phase grating mask on the plurality of optical waveguides to form diffraction gratings 23a-23h whose period is different from one another on the optical waveguides. Then, the diffraction gratings whose period is different from one another can be easily formed on a plurality of optical waveguides.;COPYRIGHT: (C)2004,JPO&NCIPI
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