| 摘要 |
PURPOSE:To obtain the distributed feedback type laser of a large amount of photo feedback and less threshold current by a method wherein a resonator utilizing Bragg's reflection due to periodical unevenness is formed at the interface between a waveguide layer and an enclosed layer, so that the side surface of this periodical unevenness makes an accurate perpendicular surface to the direction of photo radiation. CONSTITUTION:The laminated body of the lower waveguide layer 12 of N-InGaAsP, an active layer 13 of InGaAsP, the upper waveguide layer 14' of P-InGaAsP, and an auxiliary layer 20' of P-InP is formed on a substrate also serving as the lower enclosed layer 11 of N-InP. Successively, a resist mask 21 having a plurality of stripe apertures 21' is formed, and next stripe apertures 20' are formed by etching the auxiliary layer 20', thus forming a mask 20 to form the periodical unevennes in the layer 14' serving as the waveguide layer. Using the mask 20, new apertures 20''' are formed by etching the layer 14' to a depth approx. half, and accordingly the upper waveguide layer 14 having periodical unevenness is formed in the upper layer part. Since the side surface of the periodical aperture formed in such a manner is preserved as a plane perpendicular to the direction of photo radiation, a sufficient amount of photo feedback is secured, while the threshold current is reduced.
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