Optimum end reflectivity in external semiconductor lasers

The external cavity semiconductor laser is one of the suitable sources for coherent optical communication systems. Coldren and Koch 1 have given design relationships for the external cavity semiconductor laser whose facet is uncoated. However, the performance of external cavity semiconductor lasers is influenced by the reflectivity of the laser facet. The threshold and side-mode suppression ratios are calculated and represented as 3-D figures vs end reflectivities (including laser facet and external cavity mirror). The calculated optimum ranges of end reflectivities were found to agree with the experiments.