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

摘要

We propose a three-level scheme to achieve intersublevel population inversion, optical gain, and intersublevel lasing effect in n-doped InAs/GaAs self-assembled quantum dots under optical pumping. The proposed Ruby-type laser scheme uses the natural splitting of the s-p polaron intersublevel transitions around 25 μm 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 Froehlich 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.