Linewidth reduction of DSM lasers due to effects of composite cavity and distributed reflectors

Spectral properties of dynamic single-mode (DSM) lasers are theoretically analyzed in terms of the effects of composite cavity and distributed reflectors. Unique reduction mechanisms of adiabatic chirp and linewidth are found in distributed reflector (DR) lasers and complex-coupled (CC) (i.e., gain+index-coupled) DSM lasers, which are explained from the viewpoints of modal phase and modal gain behaviours. For CC-DSM lasers, it is shown that the arrangement of index and gain corrugation, namely, antiphase or in-phase combination, will suppress or enhance, respectively, an effective linewidth enhancement factor, alpha /sub eff/. Numerical results show that DR structures are much superior in spectral and single-mode properties to distributed-feedback (DFB) and distributed-Bragg-reflector (DBR) structures.<
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