Intersublevel polaron laser with InAs∕GaAs self-assembled quantum dots

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Abstract
We propose a three-level scheme to achieve intersublevel population inversion, optical gain, and intersublevel lasing effect in n -doped InAs ∕ GaAs self-assembledquantum dots under optical pumping. The proposed Ruby-type laser scheme uses the natural splitting of the s - p polaron intersublevel transitions around 25 μ m wavelength. The relaxation time engineering, which leads to optical gain in the system, relies (i) on the slow polaron relaxation from the P − state down to the S ground state, governed by the specific strong coupling regime for the electron-phonon Fröhlich interaction and (ii) on the fast nonradiative relaxation of the polaron between the P + and P − levels through the irreversible emission of acoustic phonons. TE-polarized optical gain up to 330 cm − 1 is calculated for 80 quantum dot planes in an in-plane monomode waveguide geometry and a laser pump intensity threshold as low as 930 W ∕ cm 2 , two orders of magnitude smaller than for quantum wells, is predicted.