Emission-line broadening of current tunable InAsSbP/InAsSb/InAsSbP heterostructure lasers

The dependence of emission-line broadening on the drive current was studied at 50-80 K for tunable InAsSbP/InAsSb/InAsSbP double heterostructure laser s operating in the 3.3-3.4 mum spectral region. For a small increase of the injection current I over the threshold current I-th, the line width depend s on the I - I-th difference hyperbolically, in accordance with the Schawlo w-Townes and Henry theories that assume a homogeneous distribution of the n onequilibrium carrier concentration across the resonator width. With the cu rrent raised to (3-4)I-th, line narrowing ceases and the line starts to bro aden with increasing current. The observed line broadening is explained by the effect of the nonequilibrium carrier concentration gradient between the middle of the resonator and its edges. In tunable lasers, this gradient in creases with current, the lasing wavelength simultaneously decreasing. The minimal width of the lasing line is 10-20 MHz. (C) 2000 MAIK "Nauka/Interpe riodica".