Fig. 1. High-resolution X-ray diffraction (HRXRD) diagrams of the lattice matched QCL structure. (a) Comparison between experimental measured (solid line) and theoretical simulated (blue, dashed line) HRXRD spectra; (b) enlarged image of the elliptically marked diffraction satellite peak and the corresponding FWHM

Fig. 2. Scanning electron microscopy (SEM) image of laser cross-section

Fig. 3. Performances of the device in pulse and CW modes. (a)(b) In pulse mode; (c)(d) in CW mode; (a)(c) power-current-voltage curves at different temperatures; (b)(d) relationship between wall plug efficiency and current at different temperatures

Fig. 4. Emission spectrum and beam image of the device (room temperature, CW mode, input current of 0.6 A). (a) Emission spectrum; (b) beam image

Fig. 5. Threshold current density and slope efficiency versus temperature in pulse mode

Fig. 6. Electroluminescence spectra in pulse mode (pulse width of 2 μs, frequency of 50 kHz)