A laser device based on InGaAsN quantum well active regions emitting at 1.26 mm is reported. The performances of the laser under the effect of thermal energy are investigated in terms of threshold current, Ith, gain parameter, gt, photon energy, hn, and cavity length, Lc. Four structures with one, two, and three quantum wells along with a structure that have three quantum wells with tensile strained barriers are proposed to study the relation between the peak gain, gpeak, and photon energy. The founds show that structures with one and two quantum wells operating at room temperature and under pulse wave condition, exhibit a linear dependence of gpeak on both Lc and photon energy. It is shown that the threshold current density, Jth, increases at any temperature with the cavity length Lc ranging from 250 nm to 1000 nm. Also, the investigation of the proposed structures shows that gt decreases with increasing temperature, while the ratio of the cur-rent density parameter to internal efficiency, Jt/hi, per well increases with the quantum well number. A comparison was carried out for two particular structures with three quantum wells and GaAsP barriers, the results show a decrease in the threshold current per well.