EVALUATION OF COUPLING-COEFFICIENTS FOR LATERALLY-COUPLED DISTRIBUTED-FEEDBACK LASERS

Dependence of coupling coefficient, kappa, on laterally-coupled distri buted feedback (LC-DFB) laser structure is investigated. In LC-DFB las ers, gratings are fabricated on and around the ridge after ridge-waveg uide formation and, thus, neither epitaxial regrowth nor growth on cor rugated substrates is required. For kappa calculation, coupled-mode th eory is used with the two-dimensional field intensity calculated using the imaginary-distance beam propagation method. Comparisons are made for LC-DFB lasers with different layer, ridge and grating structures a nd parameters that affect kappa are identified. In addition, it is sho wn that LC-DFB structure is less sensitive to processing variations an d, thus, more manufacturable than a conventional buried heterostructur e DFB structure.