Frequency modulation characteristics of absorptive-grating gain-coupled DFB lasers: spatial hole burning self-suppression effect

The spatial hole burning (SHB) in distributed feedback (DFB) lasers limits longitudinal-mode stability and occasionally results in spectral linewidth broadening or multiple-mode oscillation. Introduction of gain coupling is one of effective methods to reduce SHB. However, SHB may still exist in the gain-coupled (GC) DFB laser due to inappropriate coupling strength, parasitic index coupling, and facet reflection in practical devices. This paper describes self-suppression effect of SHB in absorptive-grating GC DFB lasers which is observed through the measurement of frequency modulation (FM) characteristics. This effect is attributed to the photon-density-dependent coupling coefficient in the gain-coupled cavity.<
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