High-efficiency mid-infrared transmissive Huygens dielectric metasurface

Over the past decade, major progress in emerging mid-infrared (IR) sources and detectors leads to increased interests for various IR-based applications, such as trace-gas detection, biological and medical sensing, and environmental monitoring. However, a limiting factor in the middle and long wave IR range is the lack of suitable materials that are transparent, low cost, lightweight and easy to fabricate. Here, we numerically demonstrate the artificially constructed Huygens meta-surface with versatile mid-IR wavefront control, by hybridizing the dielectric meta-atoms of high-permittivity chalcogenide on fluoride substrates. Based on the double-elements Huygens meta-atom design for linear phase tuning, transmission is enhanced substantially with high-efficiency (85%) by concentrating beam propagation into the first diffraction order similar as traditional blazed grating but with ultra-thin thickness (lambda/8). Further, based on centrosymmetric deflection to produce a local and highly focused propagation mode, a Bessel beam generator is demonstrated (lambda=5.22 mu m, NA = 0.5) by coding a well-defined phase map into dielectric meta-atoms. As a result, the proposed dielectric metasurface with nanometer level thickness shows great prospects in the field of integrated photonics.