Scientists Create Quantum Cascade Laser Nanoantenna

The device consists of an optical antenna fabricated on the facet of a quantum cascade laser emitting infrared light with a wavelength of 7 microns. The Harvard team used nanofabrication techniques to form the optical antenna, which consists of two gold rectangles, each 1.2 microns long, separated by a narrow gap (100 nm). Light from the laser illuminates the antenna, resulting in an intense spot of light in the gap of size seventy times smaller than the wavelength. This is far smaller than what would be possible with the conventional approach of forming a spot of light by focusing with a lens. Due to the wave nature of light, such a spot would have a diameter of more than 7 microns. The figure is an electron microscope micrograph of the facet of the QC laser with the built-in nanoantenna. Shown are also an atomic force microscope topographic image of the antenna and an optical image obtained with a near field scanning optical microscope, showing the highly localized light spot in the antenna gap. Credit: Harvard University