NASA's Langley Research Center has discovered a new approach to achieving a laser focal point size much smaller than the wavelength of light used, and smaller than that obtained using conventional micro zone plate lenses. The Photonic Densely Accumulated Ray-poinT (DART) technology relies on phase contrast along with interference phenomena, with or without the use of a micro zone plate lens. Coupled with the extremely small spot size, the technology also provides very high laser energy density at the pseudo focal point surrounded by destructive interference, thereby enabling a range of potential useful applications such as laser processing, lithography, nanofabrication, and optical data storage.
The NASA Photonic DART technology relies on two key aspects, one being the discovery of a new constructing interference point with an extremely fine pseudo focal point surrounded by destructive interference. A novel phase contrast method is used to achieve the constructive/destructive interference. While typical micro zone plates can be used to take advantage of the newly discovered focal point, they are not necessary; a phase contrast lens can also be used. This phase contrast method is similar in effect to the micro zone plate in the creation of constructive/destructive interference, but takes advantage of phase contrast obtained through novel 3D designs beyond the fixed binary micro zone plate design. The newly discovered central focal point in the Photonic DART technology is sharpened by the surrounding destructive interference rings present at the non-conventional focal point. The phase contrast phenomenon essentially removes the tail of the Gaussian energy distribution across the focal spot.
The ultra-small laser pseudo focal point is significantly smaller in size than the wavelength of the light used. An extremely high-intensity beam means that power density of beyond a few MW/cm2 is achievable even with a typical low-power laser.
The Photonic DART technology has potential applications in high-resolution optical lithography, high-density optical and X-ray data storage, nanofabrication, optical nano tweezers, nano-controlled physical and chemical reactions, optical manipulation of molecules and nanostructures, and scientific research.