| 摘要 |
PROBLEM TO BE SOLVED: To effectively restrain a distributed feedback laser diode from oscillating in a side mode by a method, wherein an optical coupling between a diffraction grating and light transmitted through a light waveguide layer is enhanced at the axial center of the laser diode and continuously lessened towards the both edges. SOLUTION: A distributed feedback(DFB) laser diode includes a light waveguide 22, which is provided corresponding to a light waveguide layer that extends in the axial direction (z-direction) of the laser diode and a diffraction grating 24 which is formed above the light waveguide 22 separating therefrom. The diffraction grating 24 obliquely crosses the light waveguide 22 at an angleθ, and a distance in a straight line between the light waveguide 22 and the diffraction grating 24 changes according to the axial direction. Therefore, a component of light which is transmitted through the light waveguide 22 interacting with the diffraction grating 24 can be controlled, so to be increased in intensity at the axial center of the laser diode and decreased towards the both edges. An apodization can be applied to light which interacts with the diffraction grating 24 so as to suppress a side-mode oscillation.
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