| 摘要 |
<p>PURPOSE:To obtain a variable tuning width of a large selection wavelength by forming both end faces of an element which is disposed with plural distributed feedback regions having phase shift structure and active regions in series and are coupled optically into non-reflection structure. CONSTITUTION:A lambda/4 shift diffraction grating is formed to the distributed feedback regions 201, 202 on an n-type InP substrate 110. After an InP clad layer 150 and active layer 140 of the regions 201, 202 are selectively removed, a p-type InP clad layer 160 is formed over the entire part. Grooves for electrical sepn. of amplifier regions 101, 102 and the regions 201, 202 are formed by executing mesa etching followed by embedment growth. An SiN film 170 is thereafter formed in order to decrease the reflectivity at both end faces of the element to <=1%. The oscillation of the element as a distributed feedback type laser is caused unless both end faces 170 have the nonreflection structure. Addition of the transmission prohibition wavelength region of the 2nd distributed feedback regions to the wavelength regions where the prohibition is heretofore not possible with the single distributed feedback region alone is thereby permitted and the wavelength selection width is increased.</p> |
