| 摘要 |
PROBLEM TO BE SOLVED: To attain a high optical output with good yield. SOLUTION: The distributed feedback type semiconductor laser comprises a first diffraction grating layer 12a and a second diffraction grading layer 12b which are allocated separately on both sides of a flat coupling layer 13 extended in the light emitting direction to virtually form a part of a diffraction grating 16 in the equal interval of gratings in which the phase is continuous. In this laser, a region in the upper part of the first and the second diffraction grating layers and coupling layer and in the lower part of the active layer and the coupling layer are formed with the same material substance as a semiconductor substrate, coupling coefficients k<SB>1</SB>, k<SB>2</SB>at the diffraction gratings of the first and the second diffraction grating layers are set to different values. Moreover, a reflection preventing film 22 is formed at the light emitting end surface on the side of the diffraction grating layer having a smaller coupling coefficient of the diffraction grating among the first and second diffraction grating layers. COPYRIGHT: (C)2004,JPO
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