Plasmon waveguides for terahertz quantum cascade lasers

Abstract Two possible designs of plasmon waveguides for terahertz quantum cascade lasers based on GaAs/AlGaAs are considered: using a highly doped substrate and a standard doped substrate (∼10 18 cm −3 ), but with a layer doped up to 5 × 10 18 cm −3 . Based on the results of the analysis of the minimum threshold gain for them, it was shown that the optimal solution for this type of waveguide is to use a highly doped substrate and a generation frequency lying in the range of 1.6–2.1 THz. When using a standard doped substrate, the thickness of the high- doped layer should exceed 1.1 μm. The minimum threshold gain value increases with temperature from 20 to 120 K from 9.5 to 41 cm −1 and is accessible for existing active media based on GaAs/AlGaAs superlattices.