New Method for 'Improving' Light Signals

A simple scheme for the generation and detection of "noiseless" light signals may some day improve the efficiency of information transfer via optical signal processor, computers and other high-tech devices. The theoretical basis for this novel method was developed by Prof. Gershon Kurizki and Ph.D. student Boris Sherman of the Institute's Department of Chemical Physics; parts of the study were carried out with Prof. Peter Knight and his group at Imperial College, London.

Light signals used in optical communications and computing carry minute bits of information, detected by measuring the number of photons (elementary packets of light energy) they contain. Such measurements, however, are imprecise because light signals originating even from the best lasers are inevitably distorted by "noise" due to random fluctuations in the number of photons produced. The Weizmann Institute and Imperial College researchers have suggested new strategies to reduce such "noise."

They propose the coupling of laser light output to a special storage cavity exposed to a beam of atomic particles that interacts with the light. The idea is to select those atoms that are unchanged by the cavity, which implies that the light trapped inside has a fixed number of photons, and is therefore free of "noise."

One technique involves passage of the atoms in close proximity to tiny plastic or glass spheres on which surface photons are trapped. Another possibility is the passage of atoms through a regularly spaced array of such spheres, which enables atoms to emit light in a single direction only. The new schemes are expected to be tested experimentally in the near future.