PURPOSE: To form a grating which is changed in inter-grating spacings at a desired ratio along a light propagation direction by adjusting the irradiation angle of interference beams forming interference frings by progressing while converging.
CONSTITUTION: Parallel beams are made while incident on a cylindrical lens 20 and while these beams are converged, the phase grating 30 is irradiated with such beams. The beams are made into the interference beams converging and progressing while forming the interference fringes. An optical fiber 40 is irradiated with these beams. The intervals of the brightness and darkness of the bright and dark patterns to be cast to the optical waveguide change along the light propagation direction of the optical waveguide when the optical waveguide is irradiated with such interference beams from a direction not orthogonal with the light propagation direction of the optical waveguide. At this time, the ratio of the change in the intervals of the brightness and darkness varies with the irradiation angle of the interference beams. The ratio of the change is larger as the irradiation direction of the interference beams and the light propagation direction of the optical waveguide is more approximate to parallel. The gratings formed in the optical waveguide exhibit nearly the same patterns as the patterns of the brightness and darkness to be irradiated and, therefore, the irradiation angle of the interference beams is adjusted.
HATTORI YASUJI
MOBARA MASAICHI
ITO MASUMI
INAI MAKI
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