LINEWIDTH ENHANCEMENT FACTOR IN INGAASP INP MODULATION-DOPED STRAINEDMULTIPLE-QUANTUM-WELL LASERS/

Reduction of the linewidth enhancement factor alpha is studied in InP- based strained multiple-quantum-well (MQW) lasers. Theoretical analysi s shows that the alpha-parameter is greatly reduced in modulation-dope d strained MQW lasers and may be zero while keeping positive gain. The experimental evaluation exhibits a very small alpha-parameter of arou nd 1 in InGaAsP/InP modulation-doped strained MQW lasers. As a result of the small alpha-parameter, the linewidth-power product is effective ly reduced in 1.5-mum DFB lasers with the modulation-doped strained MQ W structure. The narrow spectral linewidth around 100 kHz were also ob tained reproducibly in 1.5-mum modulation-doped strained MQW DFB laser s.