Intrinsic linewidth of the plasmonic resonance in a micrometric metal mesh

The intrinsic linewidth and angular dispersion of Surface Plasmon Polariton resonance of a micrometric metal mesh have been measured with a collimated mid-infrared beam, provided by an External Cavity tunable Quantum Cascade Laser. We show that the use of a collimated beam yields an observed resonance linewidth ? = 12 cm-1 at the resonance frequency v0 = 1658 cm-1, better by an order of magnitude than with a non-collimated beam. The extremely narrow plasmon resonance attained by our mesh is then exploited to reconstruct, by varying the QCL angle of incidence 0, the angular intensity distribution f (0) of a globar at the focal plane of a conventional imaging setup. We thus show that f (0) is better reproduced by a Gaussian distribution than by a uniform one, in agreement with ray-tracing simulation. © 2013 Optical Society of America.