Altuzarra, C.

Cencillo Abad, P.M.

Nalla, V.

Papaioannou, M.

Plum, E.

Valente, J.

Vezzoli, S.

Youngs, I.J.

Zheludev, N.

Southampton (e-Prints Soton)

Active control of light with metasurfaces J. Valente1, E. Plum1, M. Papaioannou1, P. Cencillo-Abad1, V. Nalla2, C. Altuzarra2, S. Vezzoli2,  I. J. Youngs3 and N. I. Zheludev1,2 1 Optoelectronics Research Centre and Centre for Photonic Metamaterial University of Southampton, Southampton SO17 1BJ, United Kingdom 2 Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637378, Singapore 3 Physical Sciences Department, DSTL, Salisbury SP4 0JQ, United Kingdom  Compared to natural materials, metamaterials provide an opportunity to design artificial materials with a far greater range of optical properties, such as negative, zero or extremely large refractive indicies, giant nonlinearities and novel polarization effects. However, these properties are usually static and narrowband. Therefore dynamic control of metamaterial functionalities has become the next big challenge on the route to many applications.  Here we demonstrate two distinct solutions for the active control of light with metasurfaces – two-dimensional metamaterials which could be mass-produced based on existing technology. Active control of light with metasurfaces by a control signal can be achieved in two ways: the control signal can either modify the metamaterial, or it can modify how light and metamaterial interact. We demonstrate active control of light with metasurfaces using electrical, magnetic and mechanical control signals to rearrange metasurfaces on the nanoscale (modifying the metamaterial), as well as coherent optical control signals to control the interaction of light and metamaterial from enhancement to complete suppression (modifying the light-matter interaction). Metamaterials consist of nanoscale electromagnetic resonators, the so-called meta-molecules. As the meta-molecules are strongly coupled, small displacements of their components lead to large changes of the optical properties of the metamaterial structure. We drive such actuation of arrays of thousands of meta-molecules with electrical currents, magnetic fields and directly through micromanipulation. Exploiting that electrical resistive heating bends nanostructures consisting of materials with different thermal expansion coefficients, we demonstrate 50% modulation of metamaterial optical properties. Using the magnetic Lorentz force that acts on a current-carrying nanowire placed in a magnetic field, we reconfigure metamaterial demonstrating a novel reciprocal magneto-electro-optical effect and magneto-electro-optical modulation of light at modulation rates of up to 100s of kHz. By combining mechanical and electromagnetic metamaterials on the nanoscale, we demonstrate the first nanoauxetic metamaterials, paving the way towards mechanically tuneable metadevices that conserve isotropy. Furthermore we realize the first random access electrically reconfigurable metamaterials, which may lead to spatial light modulators with sub-wavelength resolution and 3D holographic displays. Instead of modifying the metasurface, active control of light can also be achieved by controlling the light-matter interaction with an optical control signal. Here, the basic idea is that a metasurface, which is thin compared to the wavelength of light, may be placed at a node or anti-node of the standing wave formed by counter-propagating coherent beams of light. If the metasurface is placed at a node of electric field, the optical electric field cannot interact with the metasurface and therefore the electric light-matter interaction is switched off; the metasurface is effectively transparent. In contrast, the light-matter interaction will be enhanced if the metasurface is located at an electric field anti-node of the standing wave. We demonstrate that this linear approach allows control over absorption of light with light from almost 0% to almost 100% with 100 THz bandwidth, arbitrarily low intensities down to the single photon quantum limit and diffraction-limited spatial resolution.  JV would like to thank the Defence Science and Technology Laboratory (DSTL) for their support (grant DSTLX1000064081). 

Active control of light with metasurfaces

Active control of light with metasurfaces

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