Linewidth enhancement factor of 1.3 mu m InGaAsP/InP strained-layer multiple-quantum-well DFB lasers

The linewidth enhancement factor alpha in a 1.3 mu m InGaAsP/InP strained-layer multiple-quantum-well (SL-MQW) distributed feedback (DFB) laser has been evaluated from the relation between the frequency and intensity modulation indexes, and the spontaneous emission spectra below threshold current. It is demonstrated that the measured alpha -parameter of a 1.3 mu m SL-MQW DFB laser is about two, and is much smaller than that in a conventional bulk DFB laser. From the resonance frequency dependence on the output power, it is concluded that this reduction of the alpha -parameter originates in the increased differential gain. The reduction of wavelength chirping, as a result the low alpha -parameter, was experimentally confirmed for the SL-MQW DFB laser.<>