A far‐infrared dielectric waveguide laser has been decoupled from the pump laser by the use of rooftop mirrors as the cavity reflection elements. A concomitant increase in the pump and far‐ infrared output stability has resulted. Further, a new type of polarization behavior has been observed; the far‐infrared output is circularly polarized with opposite helicities above and below line center. This behavior is independent of both the pump polarization and the molecular selection rules of the particular line in question.