Potential chirpless DFB laser for InGaAs/InGaAsP compressive-strained quantum wells using modulation doping

The effects of detuning on the linewidth enhancement factor alpha are theoretically investigated for InGaAs/InGaAsP compressive-strained QW lasers. The relationship among the material gain, the Kramers-Kronig transformed differential gain, and the linewidth enhancement factor is calculated taking into account the effect of compressive strain on the valence subband structure and of p-type modulation doping. It is shown that compressive strain and/or p-type doping significantly reduces the alpha factor. It is also demonstrated that chirpless operation wherein alpha =0 can be achieved in a modulation-doped compressive-strained structure by using detuning.>