Plasmonic quantum cascade laser antenna

We report a plasmonic quantum cascade laser antenna that confines coherent midinfrared radiation well below the diffraction limit. The antenna was fabricated on the facet of a midinfrared quantum cascade laser and consists of a pair of gold nanorods separated by a gap. The antenna near field was characterized by an apertureless near-field scanning optical microscope; field confinement of about 100 and 70 nm , limited by the gap size, was demonstrated at wavelengths of 7.0 and 5.3 μ m , respectively. This device may find important applications in midinfrared subwavelength chemical and biological imaging and spectroscopy.