1.53 MU-M INGAASP-INP 1ST-ORDER LAMBDA-4-SHIFTED DISTRIBUTED FEEDBACK LASERS WITH HIGH COUPLING-COEFFICIENTS

We report on the performance of distributed feedback lasers revealing coupling coefficients as high as 330 cm-1 (K . L = 2 ... 7.5). No mode hopping is observed, stable single-mode operation at a high side-mode suppression ratio up to 51.2 dB is obtained, and the linewidths are linear with increasing reciprocal output power. Well open eyes and no bit-pattern effects are observed in 5 and 8 Gb/s "nonreturn to zero" modulations. In addition, high coupling is found to have several important advantages, e.g., lower feedback sensitivity, lower threshold gain for the Bragg mode, lower relative intensity noise, and lower influence on the facet reflectivity and on the end-facet phase resulting in a higher yield of single-mode lasers for arbitrary cleaved facets. We emphasize the discussion of high coupling coefficients, and find that such laser diodes are promising candidates for high bit rate transmission systems.