Transverse mode control of high-power single plasmon terahertz frequency quantum cascade lasers

Terahertz (THz) frequency quantum cascade lasers (QCLs) have previously been demonstrated to emit peak powers of greater than 1 W from a single facet in a single plasmon geometry. However, this was achieved by drastically increasing the laser ridge width, resulting in higher order transverse modes. In this study, we control and fully suppress these modes through metallic side-absorbers. Fundamental transverse mode operation is achieved without sacrificing THz peak power, leading to enhanced power densities. This work will open up new perspectives for using these sources in nonlinear THz physics.