According to the fundamental Huygens superposition principle, light beams traveling in a linear medium will pass though one another without mutual disturbance. Indeed, the field of photonics is based on the premise that controlling light signals with light requires intense laser fields to facilitate beam interactions in nonlinear media, where the superposition principle can be broken.
Here we challenge this wisdom and demonstrate that two coherent beams of light of arbitrarily low intensity can interact on a metamaterial layer of nanoscale thickness in such a way that one beam modulates the other.
On the basis of this approach we demonstrate that polarization effects due to absorption, anisotropy and chirality affecting an electromagnetic wave propagating through a thin slab of material can be controlled by another wave, and illustrate spectroscopic applications of these phenomena.
We also show that that the coherently controlled redistribution of energy in plasmonic metamaterials can deliver various forms of optical switching and demonstrate small-signal amplifier, summator and invertor functions. We show that these devices can operate down to single photon level and deliver a modulation bandwidth up to 100 THz.
niz@orc.soton.ac.uk