Spectral Linewidth and Linewidth Enhancement Factor in 1.5-µ m Modulation-Doped Strained Multiple-Quantum-Well Lasers

A study of the linewidth enhancement factor ( α-parameter) of 1.5-µm modulation-doped strained multiple-quantum-well (MQW) lasers is reported. The α-parameter was effectively decreased with increasing negative detuning. At a detuning of -30 nm, the α-parameter can be reduced to less than 1 by 1×10 18 cm -3 p-type modulation doping and 1.4% compressive strain in a Fabry-Perot laser. Applying this structure to a distributed feedback (DFB) laser, we investigate the dependence of the linewidth characteristics on the α-parameter. Finally, in the DFB laser with the cavity length of 1500 µm, the minimum spectral linewidth is lowered to 80 kHz at an output power of 40 mW.