| 摘要 |
PURPOSE:To realize a stable single-wavelength operation by a method wherein the laser gain is made to periodically change by laminating alternately and periodically two layers, whose forbidden band widths are different from each other, without using a diffraction grating with a periodic roughness and the imaginary component of the refractive index of laser beams is made to periodically change. CONSTITUTION:In the spectrum of a DFB laser with a refractive index, whose imaginary component is made to periodically change, the central mode coincides with the Bragg wavelength, but the threshold values of other modes become ones higher than that of the central mode. This principle is applied herein. A layer 9 with a smaller forbidden band width and an InP layer 10 with a larger forbidden band width than that of the layer 9 are periodically laminated in a plural number. By this way, carriers flow to the layer 9 with a smaller forbidden band width, the laser gain changes in every the same period as the laminated period of the layer 9 and the InP layer 10, and the imaginary component of the refractive index is made to periodically change. As a result, the purposive stable single-wavelength operation can be realized by the Bragg wavelength, which is decided by the laminated period of the layers 9 and 10 and the mean refractive index of the layer 9 and the InP layer 10.
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