Second- and higher order resonant gratings with gain or loss-Part II: designing complex-coupled DFB lasers with second-order gratings

For part I see, ibid., p. 1421, (2000). This paper deals with the investigation of second-order DFB lasers with a gain grating. It is shown that by proper choice of the duty cycle, one may take advantage of the different radiation losses between the mode with the lowest threshold gain and the second mode to increase the single-mode yield and also obtain a strong complex-coupling with high external efficiency. The impact of the random phase of high-reflection (HR)-coated facet on modal properties in an anti-reflection and HR combination is also investigated.