Electron-hole recombination in narrow-band-gapHg1−xCdxTe and stimulated emission of LO phonons

We investigate the dielectric properties of narrow-band-gap ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cd}}_{\mathit{x}}$Te under the resonant condition of the band gap ${\mathit{E}}_{\mathit{g}}$ matching the longitudinal-optic (LO) phonon energy ħ${\mathrm{\omega }}_{\mathrm{L}}$. The effect of interband transitions, which are now also induced by LO phonons, is to renormalize the mixed LO-phonon–plasmon mode downward in energy by ∼20%. We evaluate the gain in the mixed mode under conditions of population inversion and find that the stimulated emission of the LO-phonon–plasmon mixed mode from electron-hole recombination requires a pumping level of about 1–10 kW/${\mathrm{cm}}^2$. The feasibility of a stimulated-LO-phonon-emission laser is considered.