Fig. 4: Measured and simulated far-field emission patterns of THz PEPC QCLs.
From: High brightness terahertz quantum cascade laser with near-diffraction-limited Gaussian beam
a Experimental 2D far-field emission pattern of the THz PEPC QCL, where θx and θy are angles with respect to the surface normal along the longitudinal and lateral directions of the PEPC, respectively. b Experimental 1D far-field distributions of the THz PEPC QCL plotted along θx at different bias conditions. For the experimental results, the far field was measured at 13 K with pulse condition 1% (10 kHz, 4 μs). c The calculated 2D far-field pattern of the fundamental mode of the THz PEPC cavity. d, e Experimental and simulated 1D far-field emission patterns plotted along θx and θy, respectively. It can be seen that the simulation results are highly consistent with the experimental results. f Beam quality factor (M2) values for the THz PEPC QCL at different bias currents. g Brightness upscaling of THz PEPC QCL with dimension and brightness comparison with a PC QCL and a DFB QCL with a focal lens from ref. 45
