The innovation could be used to improve radio astronomy and medicine

Mar 12, 2014 10:37 GMT  ·  By
A new nanomembrane made of silicon nitrate and coated with a thin layer of aluminum is the centerpiece of a new sensitive radio wave detector developed at the NBI
   A new nanomembrane made of silicon nitrate and coated with a thin layer of aluminum is the centerpiece of a new sensitive radio wave detector developed at the NBI

Experts with the Niels Bohr Institute (NBI) at the University of Copenhagen announce the development of a new radio wave detection method, which relies on lasers to provide unprecedented sensitivity and accuracy levels. The approach could theoretically be used in a variety of fields, ranging from medicine to astronomy and quantum mechanics. 

Scientists say that radio waves are an endemic part of our daily lives today. They are used in a large number of applications, ranging from Magnetic Resonance Imaging (MRI) scanners and mobile phones to scientific experiments and observations of the Universe. However, measurements of radio wave properties are usually impaired by noise that occurs in the detectors.

The NBI team basically developed a way of using laser light to prevent the emergence of noise. As a direct consequence, measurement accuracy increases significantly, the group reports in the March 5 online issue of the top scientific journal Nature. Experts argue that heat is the main reason why noise usually occurs in detectors.

Heat usually agitates atoms and electrons alike, forcing them to move around chaotically, reducing detector sensitivity and accuracy as a result. Cooling such instruments to 5 – 10 degrees Kelvin helps, but only to some extent. This approach is very ineffective in terms of costs and unable to measure extremely faint signals, such as those produced by extremely distant radio sources in the Universe.

“We have developed a detector that does not need to be cooled down, but which can operate at room temperature and yet hardly has any thermal noise. The only noise that fundamentally remains is so-called quantum noise, which is the minimal fluctuations of the laser light itself,” says NBI expert Eugene Polzik, who is a professor and the head of the Institute's Quantop research center.

The new optomechanical device relies on interactions between optical radiations (provided by a laser) and mechanical movements (provided by a capacitor and an antenna for detecting radio waves). In this setup, the antenna picks up radio waves and then transfers them to the capacitor, which is not merely your average ensemble of metal plates. The capacitor/laser combo is the detector in this approach.

“In our system, one metal plate in the capacitor is replaced by a 50-nanometer thick membrane. It is this nanomembrane that allows us to make ultrasensitive measurements without cooling the system,” says Albert Schliesser, a research assistant professor at Quantop and the coordinator of the new experiments.

The electromechanical chip the team used in this research was developed at Nanotech, DTU. Scientific support was provided by the NBI theoretical quantum optics groups and by researchers with the Joint Quantum Institute in Maryland, the United States.