A basic analysis of complex-coupled distributed-feedback semiconductor lasers with stepwise constant coupling coefficients κ is derived. Solving coupled-wave equations at threshold reveals that the longitudinal distribution of κ as well as the relative amount of index and gain coupling plays a decisive role in the modal and spatial (internal fields) properties of complex-coupled structures. The standing-wave effect, extended to multisection devices, and the concept of apparent absorption induced by spatially dependent κ can explain the discrepancies between uniformly and nonuniformly complex-coupled structures. The complex-coupling profile is also discussed with respect to its influence on spatial hole burning and threshold gain margin, the usual criteria for optimizing sources in optical fiber telecommunication systems.
© 1998 Optical Society of America
(130.0250) Integrated optics : Optoelectronics
(140.3490) Lasers and laser optics : Lasers, distributed-feedback
(140.5960) Lasers and laser optics : Semiconductor lasers
(230.1480) Optical devices : Bragg reflectors
Thierry Fessant, "Theoretical investigation of threshold properties of purely and partly gain-coupled distributed-feedback semiconductor lasers with stepwise constant coupling coefficients," J. Opt. Soc. Am. B 15, 2689-2699 (1998)