| 摘要 |
PURPOSE:To vary a transmission band without varying a peak transmittivity by providing 1st and 2nd distribution reflectors which are separately connected so that respective reflectors may include diffraction gratings and may branch from two branch parts, and also providing a means for moving the reflection wavelength band of them. CONSTITUTION:An optical waveguide 8 is provided with two branch parts 83 and 84 between a light incident end 81 and a light emitting end 82, and the reflectors 91 and 92 having a distribution reflector structure constituted of the diffraction gratings whose pitches are respectively LAMBDA1 and LAMBDA2 are separate ly disposed on the optical waveguide 8. The refractive index of the semiconduc tor layers is varied by a current flowing across the semiconductor layers consti tuting the reflectors 91 and 92. By using the variation in the refractive index and moving the wavelength lambda0 by which respective reflectances of the distribu tion reflectors 91 and 92 are made a maximum value, the band width of emitted light POUT can be controlled so as to be a desired value. Thus, the width of the transmission band can be controlled without varying the peak transmittivity in the optical filter capable of varying the transmission band. |
