Metamaterial/graphene amplitude and frequency modulators for the active control of terahertz quantum cascade lasers

Hybrid metamaterial/graphene amplitude and frequency modulators have been implemented as external optoelectronic mirrors in external cavity configurations with terahertz quantum cascade lasers (QCLs). These devices' tunability is accomplished via the interplay between metamaterial resonant units, normally engineered in mm-size arrays, and graphene. The integration of these devices in external cavity QCLs offers unique emission features and realizes an unprecedented studied regime. The implementation of an external amplitude modulation allows the full switching of laser emission in single mode operation by electrostatically gating graphene. The introduction of more dispersive tunable architectures in frequency modulators yields additionally an all-electronic spectral laser bistability.