Generation of radiation in tunnel-coupled waveguides with positive and negative refractive indices

The possibility of generating microwave radiation in tunnel-coupled planar waveguides, one of which is made of a metamaterial and is characterized by a negative refractive index in the corresponding frequency range, while the other waveguide is active and exhibits positive refractive index, is demonstrated. The model of a tunable distributed feedback laser, in which the dependence of the refractive index of the metamaterial on the external magnetic field allows controlling the oscillation frequency, is proposed.