Spontaneous- and Stimulated-Emission Spectra of CdSnP2

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Abstract
We report the band‐edge photoluminescence spectra of CdSnP2 crystals lightly doped with Cu or Ag. The emission from CdSnP2:Cu is dominated by a broad band 0.13 eV below the band gap at 1.240 eV (2°K). The emission from CdSnP2:Ag is much stronger and is dominated by a narrow band‐to‐band emission with three impurity peaks at slightly longer wavelengths. At the very high excitation levels, possible with a pulsed N2 laser, a new band appears ∼ 15 meV below the band gap in CdSnP2:Ag, grows superlinearly in the excitation level, and has other features indicating stimulated emission. Indeed, in crystals suitably prepared to form Fabry‐Perot cavities, narrow‐line laser emission is observed. Studies in a magnetic field reveal that the spontaneous band‐to‐band transition and the new stimulated line shift to higher energies at precisely the same rate indicating that they result from the same recombination mechanism. From the observed shift to higher energies, it is argued that exciton‐exciton scattering can be unambiguously eliminated as the laser mechanism. As briefly reported previously, it is shown that the magnitude and field dependence of the shift requires proper account of electron‐plasmon (plasmaron) coupling.