Intrinsic linewidth of the Fano resonance in a micrometric metal mesh

The intrinsic linewidth of Surface Plasmon Polariton resonance in a micrometric metal mesh has been measured with a collimated mid-infrared beam, provided by an External-Cavity, tunable Quantum Cascade Laser. The use of a collimated beam yields a resonance linewidth of 12 cm -1 , much narrower than by conventional black-body sources. This opens more favorable perspectives to the use of metal meshes as sensors and detectors.