Advances in nano-optics

The new frontier of Information Technology is the confinement of single light particles in nanostructures to control their movements in the integrated circuits of the future: actually, the possibility of implementing chips where, instead of electrons, move light particles, obtaining simply unimaginable processing frequencies. There are currently some physical limits that prevent from increasing the clock frequency in conventional processors and the processing power is increased by making more CPU operate together, as it happens in multicolour microprocessors. At the Wurzburg University, in Germany, they have experimented a new control method of the light, consisting in introducing into a nano-antenna polarised light pulses, that is to say electromagnetic waves that oscillate on a well precise plan only, and guiding them along some gold nanowires, with the signals available at the guide end through another nano-antenna. In this way, they have obtained the transmission of optical signals in nanoscale, that is to say in so small structures as to be integrated into the current micro-electronic components: as a matter of fact, antennas and wave guides measure only few hundreds of nanometres. A detail, however, is missing, and here is the real innovation. Normally, photons cannot be controlled in such a microscopic scale, and not by chance it is still problematic to integrate the photon technology with semiconductors’. To overcome these limits, they have not used free photons, but “bound” photons, which appear under determinate conditions on the surface of very conductive materials, like gold: an incident light can generate some electromagnetic waves that propagate in parallel direction to the metal/dielectric interface according to the phenomenon of the surface plasmon resonance: these wave oscillations (let’s not forget that the light particles are electromagnetic waves) are actually plasmons, similar to free photons but to be confined in narrow spaces.