(Color online) Conduction band profile and the moduli squared of the relevant - and - wave functions in two adjacent stages of the proposed laser design. The bold black lines denote the active lasing levels (3: upper, 2: lower, 1: ground). The thin black lines are the injector miniband states, and the bold green lines are the continuum states . Level 4 denotes the first -state. The thin blue lines denote the doubly degenerate states, and the yellow lines are the states. The arrow denotes the lasing transition. The layer sequence of one stage (in ) starting from the barrier layer on the left is , , 12, , , , , , 34, , 30, , , , , , 19. The bold italic script denotes the barrier, the bold script the barriers, the normal script the GaAs wells, and the values in curly brackets indicate the wells. The underlined layers are -type doped with a sheet doping density of . The calculated energy difference is .
Electric field vs current density for the proposed QCL structure at the lattice temperatures of 77 K and 300 K. The solid lines are polynomial fits to the data points.
Modal gain vs current density at the lattice temperatures of 77 K and 300 K. The horizontal dashed line indicates the calculated total losses . The solid lines are linear fits to the data points in the region of relatively low current density, whose intercept with the loss line gives the threshold current density . Inset: Population inversion vs current density at 77 K and 300 K.
Electric field vs current density for the proposed QCL structure (a) and the QCL from Ref. 1 (b) at the lattice temperatures of 77 and 300 K, with and without the inclusion of the -valley transport in the simulation. The lines are polynomial fits to the data points.
(Color online) Blow-up of the wave function moduli squared of the injector miniband and the next-stage -continuum states in the proposed QCL (a) and the structure of Page et al. 1 (b), at the field of (above threshold for both structures). Black lines denote the injector states (bold black lines are the lower lasing level 2 and the ground state 1), while the green lines denote the next-stage -continuum states. Significant overlap between the injector miniband states and the -continuum states results not only in direct carrier loss to the -continuum states, but indirectly in high current through the -valley states, through the mechanism described in Ref. 4. The overlap is greater in the proposed structure (a) than the QCL of Ref. 1 (b).
Electron temperature vs current density for the proposed QCL and the QCL structure of Page et al.,1 at the lattice temperature of 300 K. The lines are polynomial fits, intended to guide the eye. Inset: Electron temperature vs input electrical power density for the two structures.
Article metrics loading...
Full text loading...