Prof Sir John Pendry, Imperial College

Controlling THz radiation with graphene

Biography

John Pendry has made seminal contributions to surface science, disordered systems and photonics. His most recent work has introduced a new class of materials, metamaterials, whose electromagnetic properties depend on their internal structure rather than their chemical constitution.

Pendry discovered that a ‘perfect lens’ manufactured from negatively refracting material would circumvent Abbé’s diffraction limit to spatial resolution, which has stood for more than a century. His innovation of ‘transformation optics’ gives the metamaterial specifications required to rearrange electromagnetic field configurations at will, by representing the field distortions as a warping of the space in which they exist.

In its simplest form the theory shows how we can direct field lines around a given obstacle and thus provide a ‘cloak of invisibility’, which was first realised at Duke in 2006. His latest work concerns application of transformation optics to plasmonic systems.

Synopsis

When graphene is doped to give a finite conductivity, it supports plasmons in the THz regime. Although these do not couple directly to external radiation, coupling can be induced by forming a grating in the graphene of a suitable period and thus produce very strong absorption of radiation but typically over a narrow band of frequencies.

Here I shall show that a suitably engineered metasurface can result in strong absorption over a wide range of THz frequencies. The effect has the potential to be switched at GHz rates.