All-dielectric metasurface absorbers for uncooled terahertz imaging

Imaging in the terahertz (THz) range of the electromagnetic spectrum is difficult owing to the lack of high-power sources and efficient detectors. For decades, there has been tremendous effort to fashion focal plane arrays for THz imaging owing to the great number of potential applications. Here, we propose and demonstrate an alternative approach which utilizes all-dielectric metasurface absorbers that act as universal converters of radiation. Incident THz waves are absorbed by the metasurface, converted to heat, and subsequently detected by an infrared camera. We realize a metasurface consisting of sub-wavelength cylindrical resonators that achieve diffraction-limited imaging at THz frequencies without cooling. The low thermal conductivity and diffusivity significantly limit the thermal conduction between neighboring pixels, thus improving the spatial resolution and imaging time. Similar to conventional metallic-based metamaterials, our all-dielectric metasurface absorber can be scaled to other bands of the electromagnetic spectrum, offering a blueprint to achieve novel uncooled bolometric imaging.