Frequency regulation of Terahertz quantum cascade lasers by changing barrier thickness

Terahertz (THz) sources with different frequency are important to gas detection. THz quantum cascade lasers (QCLs) based on resonant phonon structure with different frequency emission by changing transition barrier thickness are hereby presented. By theoretically calculation, a 0.19 nm thickening change of transition barrier would cause an approximately 350 GHz regulation range in frequency, and is then confirmed by experimental results. The corresponding far field beam profile keeps almost unchanged. With the increase of the transition barrier thickness, the output power only decreases by 15%, but the threshold current density decreases 24%. This simple method contributes to a satisfactory gas-detection approach with a stability of relative high output power.