Gain spectra modified by many-body Coulomb interactions were quantitatively calculated for one-dimensional (1D) quantum-wire lasers at various carrier densities and temperatures to investigate, in particular, robustness and 1D inherence of the gain suppression effect at the band edge. We found that the gain suppression at the band edge in the 1D case gets stronger at higher density, in a manner insensitive to temperature or spectral broadening, and results in a robust peak-gain bowing effect at all temperatures. The gain suppression is in stark contrast to the gain/absorption enhancement at the Fermi edge, which commonly occurs in 1D, 2D, and 3D and is temperature sensitive and quenches at higher temperatures. We numerically calculated gain spectra for various types of electron-hole interaction potentials and found that similar gain spectra are reproduced even when the original screened Coulomb potential is replaced by a simple contact-type potential, for which an analytical solution is available. The analysis clarified that the gain suppression effect at the band edge is a unique and inherent feature in 1D resulting from the 1D density of states.
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