Mobile phones, Wi-Fi, and satellite links are examples of communication devices predominantly using radio waves with carrier frequencies ranging up to many 10s of GHz. The data rates and reach of long-range space communications such as inter-satellite or satellite-earth links are fundamentally limited by beam divergence resulting in large loss of power as a receiving antenna only captures a small fraction of the beam. A trend in long-range transmission is therefore a transition to lightwaves instead of radio waves as a way to transmit information, which significantly reduces the beam divergence and corresponding link loss. However, these losses are still a major limitation for the reach and capacity of such links. Lightwave receivers with high sensitivity are therefore essential to enable higher data rates and longer transmission distances.
In this project, we have worked on a novel approach to detect digital information carried by lightwaves and experimentally demonstrated the most sensitive optical receiver ever reported. Light is characterized both as a wave and as particles (photons). In our receiver, we only need on average 1 photon per digital bit of information to fully recover the data transmitted. The concept operates at very high speed (which will be needed in the future) and at room temperature (in contrast to many other approaches requiring cooling down to a temperature of a few Kelvin). The key technology in our, now patented, concept is the use of a special kind of amplifier that does not generate any excess noise, in contrast to all other known optical amplifiers.
Our results have been presented at several conferences and closed seminars worldwide and have attracted significant attention from the key Space agencies in the world. We believe that there is great promise to use this technology primarily in long-haul space links where reach and capacity is essential, for example for missions to the Moon, Mars and beyond, but also for commercial inter-satellite links.
