A Higher Order Lateral Mode Suppression Scheme for Terahertz Quantum Cascade Laser Waveguides

The modal performance of a slot-clad metal-metal waveguide for terahertz quantum cascade lasers (QCLs) is elucidated in this study. Terahertz QCLs, based on metal-metal waveguides having a large ridge width, are susceptible to lase with higher order lateral modes, which may produce poor quality beams and can lead to detrimental consequences for certain applications. By comparing the modal performance of the slot-clad waveguide with previously reported designs, it has been shown that the slot-clad metal-metal waveguide can significantly enhance the degree of suppression of higher order lateral modes.