Generating structured light with phase helix and intensity helix using reflection-enhanced plasmonic metasurface at 2 <italic>μ</italic>m.

Mid-infrared (2–20 <italic>μ</italic>m) light has been attracting great attention in many areas of science and technology. Beyond the extended wavelength range from visible and near-infrared to mid-infrared, shaping spatial structures may add opportunities to grooming applications of mid-infrared photonics. Here, we design and fabricate a reflection-enhanced plasmonic metasurface and demonstrate efficient generation of structured light with the phase helix and intensity helix at 2 <italic>μ</italic>m. This work includes two distinct aspects. First, structured light (phase helix, intensity helix) generation at 2 <italic>μ</italic>m, which is far beyond the ability of conventional spatial light modulators, is enabled by the metasurface with sub-wavelength engineered structures. Second, the self-referenced intensity helix against environmental noise is generated without using a spatially separated light. The demonstrations may open up advanced perspectives to structured light applications at 2 <italic>μ</italic>m, such as phase helix for communications and non-communications (imaging, sensing) and intensity helix for enhanced microscopy and advanced metrology. [ABSTRACT FROM AUTHOR]