Terahertz Broadband Low-Reflection Metasurface by Controlling Phase Distributions

Recently, reflectionless or low-reflection surfaces made of subwavelength structures have been of broad interest in practical engineering. Here, a single-layer terahertz metasurface is proposed to produce ultralow reflections across a broad-frequency spectrum and wide incidence angles by controlling the reflection phases of subwavelength structures. To enable full control of the phase range in a continuous band, a combination of two different subwavelength elements are employed, both of which exhibit weak interactions with the incident terahertz waves, thereby showing high local reflectivities near the operating frequency. An optimization method is utilized to determine the array pattern with the minimum overall reflections under the illumination of plane waves. Both numerical simulations and experimental results demonstrate ultralow reflections of terahertz waves by the metasurface over a broad frequency band and wide incidence angles. By using the proposed metasurface, the far-field scattering patterns of metallic objects can be efficiently controlled, which opens up a new route for low-reflection surface designs in the terahertz spectrum.