“…Coherent THz waves, with a frequency range including frequencies between 100 GHz and 10 THz are promising applications for terahertz communications, detection, imaging systems, and sensing applications [14,15]. For rare-earth doped solid state lasers, the research on the dualwavelength emissions mainly focused on the Nd and Yb doped lasers in the wavelength range from 0.9 to 1.3 µm [16][17][18][19][20][21][22]. However, employing a pump laser in the 2 µm waveband will proportionally increase the quantum efficiency according to the Manley-Rowe relations, which doubles the quantum * Author to whom any correspondence should be addressed.…”