Terahertz quantum-cascade lasers based on composite right/left-handed metamaterials

A composite right/left-handed metamaterial waveguide for terahertz quantum-cascade lasers is presented. Left handed (backward wave) propagation is confirmed by using the waveguide as a leaky-wave antenna where directional beams at angles of -4° and -63° are experimentally observed at excitation frequencies 2.59 and 2.48 THz, respectively.