Since the first lasers appeared nearly 50 years ago, scientists and engineers have dreamt about creating all-optical circuits in which electrons are replaced by photons. While information is easily transmitted via light using optical fibres, switching and processing the information still rely on converting photons to electrons and then back again — which is a slow and power hungry process.
Unfortunately we are still far from seeing all-optical — or “photonic” — circuits in desktop computers and other everyday applications because these circuits require light to be manipulated in nanometre-sized spaces, something that is very difficult to do. Moreover, the efficient all-optical switching of light beams, which allows energy from one beam to amplify another, usually requires large photonic crystals.
Now, Vahid Sandoghdar and colleagues at ETH Zurich have made what they say is the world’s smallest optical transistor ever — from a single dye molecule. The device, which works by weakening or amplifying a “source” laser beam depending on the power of a second “gating” beam, could bring all-optical circuits and optical computing a step closer. By controlling the degree of attenuation and amplification via the power in a second gating laser beam, we have demonstrated the smallest optical transistor to date,” Sandoghdar said. ”
… And although our experiment was performed with conventional laser beams, the set-up also works for non-classical light beams at the single photon level,” explained Sandoghdar. “This means that quantum information processing will be possible.”