Investigation of intracavity MgO:LiNbO₃ terahertz polariton laser gain over an extended 1–5 THz range

Most intracavity MgO:LiNbO₃ terahertz polariton lasers generate output in the 1–3 THz range. In this study, we investigate the potential to extend this tuning range toward 6 THz. We predict broader tuning using a modified polariton gain theory that takes account of additional polariton damping at 3.15 THz and the angle-dependent field overlap in the crystal. We achieved continuous tuning between 1.5 and 5.4 THz and characterised the gain in this range—so far the widest THz frequency range achieved from a nonlinear crystal via intracavity SPS.