| 摘要 |
PROBLEM TO BE SOLVED: To realize element structure of a phase shift type distributed feedback semiconductor laser which can be formed by a simple method, by making the difference of propagation constants of two regions and the sum of lengths of regions where a diffraction grating is not formed satisfy a specified relation. SOLUTION: In a distributed feedback type semiconductor laser of wavelength 1.3μm band, the layer structure has a buried type diffraction grating 13 which is partly formed. In this structure, propagation constants of optical waves are a little different from each other, in the region 18 where the buried type diffraction grating exists and the region 19 where it does exist, in a resonator having a length of Lc. Between the differenceΔβof the propagation constants and the sum Ls of the region 19 where the grating is not formed, in order to satisfy a relation 0.4π<Δβ.Ls<0.6π, Ls is so adjusted that the productΔβ.Ls becomes equal toπ/2. Therefore, an equivalentλ/4 shift type diffraction grating can be obtained, so that a high output distributed feedback type semiconductor laser capable of a stable single mode, and an optical module mounting the laser can be realized by very easy technique.
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