Band profile for the simulated quantum cascade laser. One module is indicated by a rectangular box. From left to right, the layer thicknesses of one module are 5.4/7.8/2.4/6.4/3.8/15.3/3.5/8.8 in units of nanometers, where the barriers are in boldface and GaAs wells in plain text. The underlined 15.3 nm GaAs well is doped to , yielding a sheet density of . The applied electric field is .
The lifetimes of radiative states (left) and the nonradiative relaxation time (right) as a function of applied biases.
Current density for a range of applied biases. Squares are the simulated results. The full line represents the measured curve accounting for a series resistance and the dashed line accounting for a parallel resistance based on the full line. The experimental results are measured at a heat sink temperature of 10 K. The injection anticrossing occurs at . The inset is the band profile under an applied bias of .
Population density in radiative states (a) and gain (b) for a range of applied biases. Also indicated is the calculated threshold gain value for a metal-metal ridge structure with uncoated facets.
Schematic profile of metal-metal waveguide structure and parameters for the calculation of the waveguide loss.
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