Experimental studies of injection lasers: spontaneous spectrum at room temperature

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Abstract
The current dependence of the spontaneous and coherent intensities and differential intensities from GaAs injection lasers operated at 300 K is reported. A compensated material with single heterojunction and a low‐doped double heterojunction unit were studied. While the spontaneous intensities rise smoothly with current at all power levels, the differential intensities show structure associated with onset of lasing. At threshold there is a sharp cusp, indicating a change in the internal dynamics. The data are found to be consistent with 100% radiative recombination but do not exclude nonradiative transitions. New features are negative differential intensity of lasing; a logarithmic increase of Fermi level with current in the lasing region; and marked differences of the spreading of the lasing spectrum and of the current saturation of the two lasers.