Patent ID: 6842568

Claim:
A method of making a diffraction grating device, in which an optical waveguide is irradiated, by way of a phase grating mask, with refractive index modulation inducing light capable of inducing a refractive index modulation in a predetermined region of said optical waveguide so as to form a diffraction grating in said predetermined region, said method comprising: a diffraction efficiency distribution measuring step of measuring a diffraction efficiency distribution of said phase grating mask; and a refractive index modulating step of longitudinally scanning said optical waveguide with said refractive index modulation inducing light by way of said phase grating mask and irradiating said optical waveguide with said refractive index modulation inducing light so as to modulate a refractive index of said predetermined region; wherein, in said refractive index modulating step, upon scanning with said refractive index modulation inducing light, longitudinal relative positions of said phase grating mask and said optical waveguide are changed according to said diffraction efficiency distribution of said phase grating mask.