Absorption, emission, and gain spectra of 1.3 µm InGaAsP quaternary lasers

The spontaneous emission spectrum of mesa lasers was analyzed to determine the absorption and gain spectra at threshold. The radiative current density at threshold was found to be 4.4 kA cm^-2μm^-1, which is 60 percent of the total current density for the lowest threshold mesa laser. The increase in radiative lifetime due to reabsorption of emitted radiation was calculated to be 1.5, using file measured absorption and emission spectra. Contrary to other studies, our investigation of an LED and 3 lasers of different types yielded no evidence of carrier heating.