Metamaterials and Metasurfaces


A. Boltasseva and H.A. Atwater, Science 331 290 (2011).

Tunable Metamaterials

Electromagnetic metamaterials are artificial materials comprised of nanostructures. They attract the interest of different fields of nanoscience because they offer unique optical functionalities like optical magnetism, negative refraction and epsilon-near-zero response. Thus, they hold great promise for applications such as perfect lensing and optical tunneling, among many others.

We are interested in developing analytic and numerical algorithms for understanding and describing the optical response of metamaterials that can enable us to precisely engineer their electromagnetic properties and investigate their potential as novel optical components and devices. In our group, effort is being put in building non-local parameter retrieval techniques for metamaterials in optical frequencies, where the plasmonic effects become important.

Until now, the response of metamaterials has been fixed at the time of metamaterial fabrication and active control of the collective response of metamaterials has not yet been the primary goal. The research in our group also aims to develop, realize and characterize metamaterials whose response can be tuned dynamically and we are interested in studying different potential tuning mechanisms that can provide frequency tunable metamaterials,

Epsilon-near-zero (ENZ) and negative index metamaterials

We are particularly interested in two of the most famous theoretically predicted optical functionalities of metamaterials: epsilon-near-zero and negative index metamaterials.

The epsilon-near-zero response of matter can give rise to exciting properties in its interaction with the electromagnetic waves. Specifically, the low wave number provided by ENZ metamaterials forces the phase advance of light passing through an ENZ region to go to zero. Thus, the AC nature of the field changes to a DC-like behavior. This optical tunneling effect is important for optical waveguiding and for squeezing the electromagnetic energy into ultra-small regions. Furthermore, the ENZ response of matter can improve the coupling and energy transfer between quantum emitters, which can effectively contribute to the efforts toward an all-quantum-computer. However, materials with near zero permittivity already exist in nature especially in noble metals, but the ENZ region is fixed in the infrared region. The tunability of metamaterials enables the shift of the ENZ region towards the spectral region of each potential application.

The research towards a negative index material dates back to 1960s, when Victor Vesalago first described the conditions for a negative index metamaterial. Negative refractive index materials do not exist in nature and people have been working in designing and fabricating negative index metamaterials in the microwave and in the optical regime. We are interesting in building an isotropic and tunable negative index metamaterial because the control of both the phase and amplitude of such a device opens the route towards holographic display, a cloaking device, a perfect lens, among many others.