Scientists in Denmark and the US have developed a new approach to detecting and strengthening ultra-weak radio signals they say could benefit a range of industries.
According to the researchers, detecting extremely weak radio waves is key to many modern technologies, including satellite navigation, long-distance communications, radio telescopes and magnetic resonance imaging (MRI) systems. However, energy loss, noise problems and specialized cooling requirements have hindered the abilities of the sensitive instruments used in each field.
Now, researchers from the University of Copenhagen, Denmark; the Technical University of Denmark and the Joint Quantum Institute at the University of Maryland have created a new radio band detector that converts ultra-weak radio waves into light, “providing the first all-optical detection of microwaves and other radio band waves while reducing background noise a thousand times better than existing methods.”
The technology offers two distinct advantages, the researchers say. First, the conversion of a radio signal into light helps prevent energy loss, as light is transmitted via an optical fiber instead of a copper wire. Second, the device mitigates noise at room temperature, removing the need for expensive and inconvenient cryogenic cooling methods.
According to the researchers, the device works like this: “radio waves strike an antenna which constitutes one element in an electronic circuit. Another element in that circuit is a device with two electrodes called a capacitor. One of these electrodes consists of a flexible membrane. Light at visible frequencies reflects off the back side of this membrane. Depending on the radio signal arriving at the antenna, the silicon-nitride membrane (coated with a 50-nm-thick film of silver) mechanically alters its shape accordingly.”
“In the first place, this is a completely new way to measure electrical signals: making them excite a tiny membrane which we monitor with laser light,” team leader Albert Schliesser of the Niels Bohr Institute said. “It may sound surprising, but this approach is so sensitive that it can out-perform conventional electronic amplifiers. That means, for example, that it could be a new way of getting clearer MRI images, or maps of the sky recorded by radio telescopes. We are currently trying to extend our work—which so far is really just a demonstrator of the concept—to attain a smaller detector which is more sensitive and capable of handling a wider band of radio signals.”
Their research is published in the journal Nature.