Numerical optimization of gain region in dual-upper-state quantum cascade laser

The advanced simulation tool which utilizes the non-equilibrium Green’s function (NEGF) method is employed to analyze and improve the gain region in the quantum cascade laser. The device under consideration is tailored for the emission of 11.5 µm wavelength radiation and is supposed to find an application in trace sensing of BTEX (benzene, toluene, ethylbenzene, and xylene) gases. The applied optimization strategy was to tune the width of the injection barrier responsible for the laser pumping. It is shown that the improvement of the structure is possible by thinning the injection barrier by 0.3 nm. The results of the calculations show that the output optical power from the device with a thinner injection barrier increases by ∼ 30%.