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(a) Absolute square of the Wannier states of the QCL from Ref. 3 together with the heterostructure potential. (b) Same data for the device proposed here. The layer sequence is 17.5/1.5/11.5/3 nm with effective masses of 0.067 in the wells and 0.0919 in the barriers (bold symbols). The conduction band offset is 0.27 eV, which relates to a structure. The underlined barrier is n-doped with . [Note that Wannier states are not the commonly plotted eigenstates of the Hamiltonian but are better localized within the period (Ref. 8).]
Simulation results for the proposed structure of Fig. 1(b) at different lattice temperatures. (a) Current vs bias per period. (b) Gain spectrum at a bias of 48 mV per period.
Electron density at 200 K for the first current peak at 37 mV per period (upper panel) and the lasing operation point at 48 mV per period (lower panel). In addition the electronic eigenstates are shown, which clearly show the mixing of the Wannier states at the respective resonances.
Calculated quantities for the gain transition at 48 mV per period. If the upper laser level were in thermal equilibrium with its injector level, one would expect , which is a lower bound for the population of the lower laser level, , being in resonance with the injector level.
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