Optics with hyperbolic materials [Invited]

A hyperbolic material (HM) is an optical material that exhibits a unique property of having anisotropy with simultaneously different signs of the permittivity tensor components. Such a property leads to novel optical phenomena. HM can host highly localized bulk plasmon polaritons and directional surface waves with the large wavevectors required in various applications in nano-guiding, sensing, and imaging. Research on HMs has been intensified in the last decade thanks to progress in nanofabrication and advances with two-dimensional materials. This paper reviews the recent developments in novel structures and materials with hyperbolic materials such as metasurfaces, hypercrystals, waveguides, and cavities. Furthermore, various applications that take advantage of the unique optical phenomena of HMs are covered, including negative refraction and photonic spin Hall effect for optical signal sorting, super-resolution, refractive index sensing, and mid-infrared vibrational spectroscopy.