Reconfigurable Metasurfaces in the Infrared

Abstract

Recently there has been great interest in the applications of infrared (IR) light in many areas, including infrared imaging, trace-gas detection, biological and medical sensing, and environmental monitoring. Over the last decade, there has been major progress in the development of new IR sources and detectors. However, a limiting factor in the development of IR optics is the lack of suitable materials that are transparent, low cost, lightweight, and easy to fabricate. A new class of optical components based on metasurfaces could be used to overcome these limitations. In contrast to conventional optical components that achieve wavefront engineering by phase accumulation through light propagation in the medium, these components control the wavefront of light using arrays of optical resonators with subwavelength dimensions, which are patterned on a surface to introduce a desired spatial profile of optical phase. By tailoring the properties of each element of the array, one can spatially control the phase, amplitude, and/or polarization of the scattered light and consequently mold the wavefront. Their exceptional optical properties have led to the development of ultrathin optical devices with various functionalities outperforming their conventional bulky counterparts or demonstrating new optical phenomena covering a wide range of spectrum from the visible to the terahertz. However, most of the metasurface devices are static, limiting the functions that can be achieved. In this thesis, reconfigurable metasurface devices at IR wavelengths based on three types of tuning mechanisms are designed and fabricated: (1) a metasurface absorber and a metasurface polarizer based on a phase transition material, vanadium dioxide (VO2); (2) a metasurface lens integrated with a Micro-Electro-Mechanical System (MEMS); (3) a metasurface lens and aberration corrector based on dielectric elastomer actuators (DEAs). These devices were designed to operate in the long-wave IR (LWIR, 8 – 14 µm), mid-wave IR (MWIR, 3 – 5 µm), and short-wave IR (SWIR, 1 – 3 µm), respectively. However, the design principles of these devices can be generalized to other wavelength ranges.