john pendry

Extreme Time Modulation of Material Properties and Hawking Radiation

Experiments demonstrating extremely rapid modulation of the permittivity have been performed by exploiting the enhanced non-linear effects possible in the presence of plasmonic resonances. These experiments measure an extreme rise time by exploiting the analogy between Young's slits which produce diffraction in momentum space, and closely spaced time windows which produce diffraction in frequency space. I go on to discuss some theoretical consequences of space-time modulated structures. Diffraction gratings moving at trans-luminal velocities contain points where wave and grating velocity are equal. We show these points can be understood as a series of optical event horizons where wave energy can be trapped and amplified, leading to radiation from the quantum vacuum state. We calculate the spectrum of this emitted radiation, finding a quasi-thermal spectrum with features that depend on the grating profile, and an effective temperature that scales exponentially with the length of the grating, emitting a measurable flux even for very small grating contrast. Stimulated emission also takes place under the influence of incident photons, but in contrast to emission from excited atoms, transluminal systems radiate correlated photon pairs.

John PENDRY is a condensed matter theorist working at Imperial College London. His early work addressed electronic and structural properties of surfaces developing the theory of low energy diffraction, EXAFS, and of electronic surface states later moving on to studies of transport in disordered systems. In the mid 1990's he turned his attention to metamaterials and proposed several structures which radically influenced the development of the field leading to the experimental discovery of negative refraction by the Smith group and later, also in collaboration with David Smith, the design of a cloak of invisibility. His investigation of negative refraction led to the discovery that it is theoretically possible to design a lens whose resolution is limited only by the perfection of manufacture, not by the well known Abbé law which limits resolution to the order of the wavelength. The technique of transformation optics which he pioneered has led to many applications in the field of plasmonics, particularly building on the perfect lens concept and showing how to concentrate light into sub nanoscale volumes. His most recent work is the topic of today's talk and moves the study of metamaterials on to structures that vary in time as well as in space.