Extraordinarily Transparent Metaldielectrics for Infrared and Terahertz Applications

Metamaterials are extremely important in advanced technologies, but usually, they rely on the resonant behavior of their constituent blocks. This strongly limits the application of metamaterials to particular frequency band ranges. However, metamaterials with broadband behaviors are highly desirable and are essential for many applications. Herein, recently discovered metamaterials that are composed of densely packed metallic nanoparticles but behave as effective dielectrics are explored. Such metamaterials are extremely transparent for all wavelengths within or exceeding the near infrared and their performance is constant across an ultra‐broadband range of frequencies, which is vital to many devices that operate across the same frequency range. The ability to tune the refractive index of these metamaterials to unnaturally high values while maintaining transparency opens new avenues, such as creating flat, thin metalenses in the terahertz region where only bulk lenses are currently available. To highlight those features, several new possible infrared and terahertz applications of these metamaterials which push the boundary of existing technology in THz photonics are shown.