Patent ID: 6021242
Filing Date: 2000-02-01
Classification: G02B

Abstract:
A diffraction grating type band-pass filter in which a diffraction grating area having a periodic refractive index change along an axial direction is formed within an optical waveguide and is adjusted so as to transmit therethrough light in a predetermined wavelength band;said diffraction grating area comprising a plurality of areas divided in an optical axis direction and having:first and second periodic refractive index variable areas in which refractive index is varied with a period monotonously changing along the axial direction with substantially a constant changing width of .DELTA.n so as to form a plurality of diffraction gratings, the shortest period of one area being longer than the longest period of the other;a zero area, disposed between said first and second periodic refractive index variable areas, having substantially a constant refractive index; andfirst and second boundary areas, respectively disposed between said zero area and said first and second periodic variable refractive index areas, in which the changing width of refractive index continuously and monotonously changes between .DELTA.n and 0.