Theoretical analysis of quantum well fountain and Raman laser schemes for far-infrared and THz generation

A theoretical analysis of fountain and Raman laser schemes based on semiconductor heterostructures with quantum wells and suited to generation in the far-infrared and THz range is conducted. It is shown that for a metal–metal waveguide and a heterostructure design optimal for lasing at 100 µm, a threshold mid-infrared pump intensity (inside the active region) for generation at this wavelength is ≅240 kW cm-2. The maximum output power (in the pulsed regime, from one strip per one facet) is estimated to be 0.4 W and achieved at the pump intensity 4.8 MW cm−2 when the generation wavelength is shifted to 85 µm. Stability analysis is carried out and domains of steady one-frequency generation as well as non-stationary lasing are found. The fountain and Raman quantum well lasers of the far-infrared and THz range could become an alternative for quantum cascade lasers whose advances in this frequency region encounter serious problems