Metasurfaces use optically thin arrays of optical scatterers, such as antennas, with subwavelength sizes and separations to afford a spatially varying optical response. Metasurfaces enable new physics and phenomena that are distinctly different from those observed in three dimensional (3D) metamaterials, providing us with the unique capability to fully control light with planar elements and thus realize “planar photonics”[1], [2]. An excellent example of this is the discovery of the generalized laws of reflection and refraction [3] that enable to redirect an incident beam in any direction of space by endowing the metasurface with a phase gradient that acts as a quasi-wavevector in the lateral momentum conservation law.   It is the reduced dimensionality of optical metasurfaces that opens up new physics and novel functionalities that will be explored in this MURI.

Metasurfaces  have shown that they provide unprecedented design flexibility: one can engineer their interaction with the electric as well as the magnetic field components of light independently, which leads to complete control of not only the phase, amplitude and polarization response but also of the local impedance response of the metasurfaces. This control is not limited to a single wavelength but can be broadband by suitable dispersion engineering of the constituent elements of the metasurfaces. 

In this Multidisciplinary University Research Initiative our team will explore the topics illustrated above:

(1) Constituent Materials Building Blocks that offer new functionalities such as active tuning of the optical properties by external stimuli and reduced optical losses.

(2) The Physics of Metasurface Devices, discovering new phenomena that enable full control of scattered and guided light using optically thin photonic devices.

(3) Metasurface Platforms such as Metatronics with the goal of establishing new design tools and realizing large-area and multi-layered metasurfaces capable of incorporating active, nonlinear, and low-loss materials for full control of light-matter interaction .

(4) Quantum Metasurfaces by integrating non-classical light sources such as single photon emitters with arrays of properly designed optical scatterers, thus endowing metasurfaces with quantum information processing capabilities. 

(5) Active Metasurfaces where local control of amplitude, phase and polarization of light will provide us with complex functionalities such as fast wavefront control, beam forming and steering, pattern synthesis, polarization controlled waveguiding and routing, light emission manipulation. 

Our effort is focused on exploring the new physics afforded by metasurfaces that can lead to breakthrough applications in photonics and in particular active metasurfaces that are reconfigurable and/or tunable in real time with external control of their optical characteristics, including distinctively quantum properties such as single photon emission

Exploration of the underlying physics will focus on the connection between active metasurface design and the control of surface polaritons and reflected/transmitted beams and on the interaction of device building blocks (optical antennas, dielectric resonators, quantum emitters, etc.) with metasurfaces including nonlinear metasurfaces for broadband frequency conversion.  

On the materials side the focus will be on materials suitable for flat and conformal 2D structures and with desired light-matter interactions, which offer reduced optical losses and new functionalities such as active tuning of the optical properties, such as transparent conductive oxides, semiconductors, transition metal nitrides, phase change materials and graphene. 

Using the notion of metatronics (equivalent optical circuits) metasurface building blocks will be configured into large-area, single and multilayered metasurface platforms, to achieve new functionalities. 

Funded by U.S. Airforce Office for Science Research Grant # FA9550-14-1-0389