FORMATION OF OPTICAL WAVEGUIDE TYPE DIFFRACTION GRATING AND FORMING DEVICE THEREFOR

摘要

PURPOSE: To provide a forming device for optical waveguide type diffraction gratings having diversified reflection characteristics. CONSTITUTION: An optical fiber 1 has a core added with Ge and the refractive index of its core part increases when the core part is irradiated with light of a wavelength about 240nm. A UV laser beam 2 having such wavelength is bisected by a beam splitter 3 and the flank of the optical fiber 1 is irradiated with the respective beams via first and second masks 6, 7 from mirrors 4, 5. The bisected laser beams interfere with each other in the core part of the optical fiber 1 and the core part is irradiated with the interference fringes. The first and second masks 6, 7 have the transmission characteristics of the transmittance of light distributing with arbitrary sizes and changing shapes in a longitudinal direction and independently control the modulation quantity distribution and average refractive index distribution along the longitudinal direction of the diffraction gratings formed on the optical fiber 1.