Planar heterogeneous structures for coherent emission of radiation.

The coupling of excited surface polaritons with thermal radiation through diffraction by gratings results in coherent thermal emission in a certain frequency range toward well-defined directions for p polarization. A planar coherent source is proposed that uses multilayers of negative permittivity (epsilon) and negative permeability (mu) materials. Owing to the excitation of surface polaritons at the interface between the negative-epsilon and negative-mu layers, coherent emission can be achieved for both s and p polarization. Moreover, one can control the emission frequency and direction by adjusting the layer thicknesses.