Comparison of quasi-symmetrical and asymmetrical mode beatings in two-section partially gain-coupled DFB lasers

The self-consistent mode-beating model is applied to a two-section partially gain-coupled distributed feedback (TS-GC DFB) laser with low coupling strengths. The model is based on introducing a fixed detuning parameter to the governing rate equations of the slowly-varying fields. The existence of quasi-symmetrical, a mix of quasi–symmetrical and asymmetrical, and asymmetrical mode beating depends on the coupling strength of the cavity. The quasi-symmetrical mode beating predicted here is similar in characteristics to the mode beating found in index-coupled self-pulsating lasers. It has a continuous and a wide tuning range. The asymmetrical mode beating is capable of producing self-pulsations over multiple self-pulsating regimes and higher self-pulsating frequencies than the quasi-symmetrical mode beating.